Biochemistry Quiz on Metabolites

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Questions and Answers

Which of the following is NOT classified as a primary metabolite?

Atropine (correct)

Citric acid

L-lactate

Ethanol

Primary metabolites play a crucial role in an organism's growth and reproduction.

True

What is the role of secondary metabolites in organisms?

Ecological functions such as defense mechanisms and antibiotic production.

___ is a secondary metabolite derived from various plants with important clinical uses.

Atropine Signup and view all the answers

Which organism is known for producing citric acid?

Aspergillus niger Signup and view all the answers

Secondary metabolites are formed primarily during the growth phase of an organism.

False Signup and view all the answers

Name one example of a secondary metabolite used in industry.

Erythromycin or Bacitracin Signup and view all the answers

Match the following primary metabolites with their uses:

Ethanol = Used for large-scale production in industrial microbiology Citric acid = Widely used in food production L-glutamate = Commonly used as a dietary supplement L-lysine = Important amino acid for nutrition Signup and view all the answers

What type of receptors does atropine act on?

Muscarinic receptors Signup and view all the answers

Erythromycin is produced from organisms classified under Bacillus subtilis.

False Signup and view all the answers

What is the primary process by which plants convert light energy into chemical energy?

Photosynthesis Signup and view all the answers

The light-dependent reactions of photosynthesis occur in the ______ of the chloroplast.

thylakoid membranes Signup and view all the answers

Match the following steps of the Calvin cycle with their descriptions:

Carbon fixation = Combines CO2 with RuBP Reduction = Converts 3-PGA into G3P Regeneration = Recycles G3P to regenerate RuBP Signup and view all the answers

Which of the following substances is produced during the light reactions of photosynthesis?

NADPH Signup and view all the answers

Bacitracin is commonly used as an oral antibiotic.

False Signup and view all the answers

What is the final product of glycolysis?

Pyruvate Signup and view all the answers

The chemical equation for the light reaction of photosynthesis can be simplified to: 2H2O + 2NADP+ + 3ADP + 3Pi → O2 + ______ + 3ATP

2NADPH Signup and view all the answers

Match the following biochemical pathways with their description:

Glycolysis = Converts glucose into pyruvate Citric Acid Cycle = Oxidizes acetyl-CoA to produce ATP Calvin Cycle = Incorporates CO2 into sugar molecules Signup and view all the answers

Which of the following is a reactant in the dark reactions of photosynthesis?

ATP Signup and view all the answers

Which of the following vitamins is classified as water soluble?

Vitamin C Signup and view all the answers

Chlorophyll a is the main pigment in most green plants.

True Signup and view all the answers

Vitamins can be synthesized by the body.

False Signup and view all the answers

What is the initial acceptor molecule in the Calvin cycle?

Ribulose-1,5-bisphosphate (RuBP) Signup and view all the answers

The Krebs cycle takes place in the ______ of the mitochondria.

matrix Signup and view all the answers

What is the primary natural form of Vitamin A?

Retinol Signup and view all the answers

Excessive intake of _______ soluble vitamins may be toxic.

fat Signup and view all the answers

Which vitamin is referred to as the 'sunshine vitamin'?

Vitamin D Signup and view all the answers

Beta-carotene can be converted into Vitamin A by the body.

True Signup and view all the answers

What is the role of Vitamin D in the body?

It assists in the absorption of calcium and phosphorus. Signup and view all the answers

Vitamin _______ is essential for vision, growth, and immune function.

A Signup and view all the answers

Which of the following dietary sources is rich in Vitamin E?

Nuts and seeds Signup and view all the answers

Match the following vitamins with their primary deficiency states:

Vitamin A = Xerophthalmia Vitamin D = Rickets Vitamin C = Scurvy Vitamin B = Beriberi Signup and view all the answers

How are fat-soluble vitamins absorbed in the body?

With lipids Signup and view all the answers

Vitamin E is a specific term for one particular form of tocopherol.

False Signup and view all the answers

What condition can arise from Vitamin D deficiency in adults?

Osteomalacia Signup and view all the answers

The vitamins can be classified as either _______ soluble or water soluble.

fat Signup and view all the answers

Which vitamin is primarily derived from plant sources such as mushrooms?

Vitamin D2 Signup and view all the answers

What is the primary location where the Krebs cycle occurs?

Matrix of mitochondria Signup and view all the answers

The shikimic acid pathway is utilized by plants only for synthesizing fatty acids.

False Signup and view all the answers

What are the two substrates that start the shikimic acid pathway?

Phosphoenolpyruvate and erythrose-4-phosphate Signup and view all the answers

The main product of the mevalonate pathway is __________.

cholesterol Signup and view all the answers

Match the following metabolic pathways with their main products:

Shikimate pathway = Phenolic compounds and aromatic amino acids Malonate pathway = Fatty acids Mevalonate pathway = Cholesterol and isoprenoids Signup and view all the answers

Which of these compounds is considered a building block in biosynthesis?

Acetyl CoA Signup and view all the answers

The acetate pathway is primarily for synthesizing amino acids.

False Signup and view all the answers

What are the main intermediates produced by the mevalonate pathway?

Isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) Signup and view all the answers

C2 building blocks in biosynthesis are derived from __________.

acetyl-CoA Signup and view all the answers

Match the following pathways with their type of secondary metabolites:

Shikimate pathway = Alkaloids and phenolic compounds Malonate pathway = Fatty acids Mevalonate pathway = Terpenes and steroids Signup and view all the answers

What initiates the shikimic acid pathway reactions?

Phosphoenolpyruvate Signup and view all the answers

Environmental stresses do not influence the expression of secondary metabolites.

False Signup and view all the answers

Name an enzyme involved in the shikimic acid pathway.

DAHP synthase Signup and view all the answers

Malonyl-CoA is formed from __________ by the addition of CO2.

acetyl-CoA Signup and view all the answers

Which acid is a key precursor in the biosynthesis of aromatic amino acids?

Shikimic acid Signup and view all the answers

Which of the following is a common dietary source of Vitamin E?

Wheat germ oil Signup and view all the answers

Vitamin K is primarily involved in blood clotting and can help in the metabolism of bone proteins.

True Signup and view all the answers

Name one symptom of Vitamin E deficiency.

Muscle weakness Signup and view all the answers

Vitamin B1 is also known as _____ .

thiamine Signup and view all the answers

Match the following vitamins with their primary functions:

Vitamin K = Blood clotting Vitamin B2 = Energy metabolism Vitamin B3 = Neurological protection Vitamin E = Antioxidant activity Signup and view all the answers

What is a major health consequence of Vitamin K deficiency?

Hemorrhage Signup and view all the answers

Riboflavin is sensitive to light and can change to lumichrome or lumiflavin.

True Signup and view all the answers

What is the common deficiency condition associated with Vitamin B3?

Pellagra Signup and view all the answers

Vitamin B2 is also known as _____ .

riboflavin Signup and view all the answers

Which vitamin is described as a lipid-soluble antioxidant?

Vitamin E Signup and view all the answers

Thiamine is stable in an acidic environment but decomposes above pH 5.0.

True Signup and view all the answers

Identify one dietary source of Vitamin B1.

Whole grains Signup and view all the answers

Niacin is also called _____ .

nicotinic acid Signup and view all the answers

Match the following vitamins with sources:

Vitamin E = Plant oils Vitamin K = Green leafy vegetables Vitamin B1 = Legumes Vitamin B2 = Yeast Signup and view all the answers

Which plant is known for containing cardiac glycosides and has historically been considered poisonous?

Nerium oleander Signup and view all the answers

Ouabagenin has an aldehydic group at C-10.

False Signup and view all the answers

What is the main therapeutic effect of Strophanthin when administered intravenously?

It acts as a cardiotonic. Signup and view all the answers

The sugar component of Ouabagenin is ______.

rhamnose Signup and view all the answers

What vitamin is known for its role in energy metabolism and synthesis of lipids?

Vitamin B5 Signup and view all the answers

Match the following substances with their properties or uses:

Oleanderin = Used for treating cardiac insufficiency Red squill = Used as rat poison Strophanthidin = Cardiotonic used I.V. Squill glycosides = Expectorant properties Signup and view all the answers

Vitamin B6 is primarily found in animal tissues and is used for amino acid metabolism.

True Signup and view all the answers

What condition can arise from a deficiency of Vitamin B12?

Pernicious anemia Signup and view all the answers

Vitamin C is essential for the synthesis of __________.

collagen Signup and view all the answers

Match the vitamin to its key use:

Vitamin B5 = Energy metabolism Vitamin B9 = DNA synthesis Vitamin B7 = Fat metabolism Vitamin C = Antioxidant activity Signup and view all the answers

Which vitamin is primarily involved in mood improvement and red blood cell formation?

Vitamin B6 Signup and view all the answers

Deficiency in Vitamin B7 can lead to fatigue and dermatitis.

True Signup and view all the answers

List one major food source of Vitamin C.

Citrus fruits Signup and view all the answers

Vitamin B9 is particularly important during __________ to prevent birth defects.

early pregnancy Signup and view all the answers

Which vitamin is known for aiding in the absorption of iron?

Vitamin C Signup and view all the answers

Glycosides are organic compounds that contain a sugar and a non-sugar moiety.

True Signup and view all the answers

What vitamin helps in the maintenance of nerve fibers?

Vitamin B12 Signup and view all the answers

Vitamin B12 is also referred to as __________.

cobalamin Signup and view all the answers

Match the vitamin with its deficiency symptoms:

Vitamin B6 = Peripheral neuropathy Vitamin B5 = Fatigue and sleep disturbances Vitamin C = Scurvy Vitamin B9 = Megaloblastic anemia Signup and view all the answers

Which form of glycosides predominates in plants?

β-glycosides Signup and view all the answers

Most glycosides are soluble in non-polar organic solvents.

False Signup and view all the answers

What are the two main components of glycosides?

glycone and aglycone Signup and view all the answers

The acidic hydrolysis of glycosides results in the cleavage of the ________ linkages.

glycosidic Signup and view all the answers

Match the following types of glycosides with their examples:

O-glycosides = Senna C-glycosides = Cascaroside S-glycosides = Sinigrin N-glycosides = Glycoalkaloid Signup and view all the answers

Which enzyme specifically hydrolyzes most β-glycoside linkages?

Emulsin Signup and view all the answers

Glycosides can be classified based on the chemical nature of the aglycon.

True Signup and view all the answers

What is the primary role of the glycone part of glycosides in biological systems?

solubility properties Signup and view all the answers

Glycosides derived from digitalis are commonly used for ________ effects.

cardiac Signup and view all the answers

What is the taste characteristic of most glycosides?

Bitter Signup and view all the answers

Enzymatic hydrolysis of glycosides can occur within the same plant.

True Signup and view all the answers

Name one glycoside that is used as a laxative.

Senna Signup and view all the answers

________ glycosides are classified based on the type of glycosidic linkage.

α and β Signup and view all the answers

Match the following glycoside types with their respective sugars:

Glucoside = Glucose Galactoside = Galactose Mannoside = Mannose Arabinoside = Arabinose Signup and view all the answers

Which of the following is a process involved in the purification of plant material from seeds?

Defatting Signup and view all the answers

Cardioactive glycosides are only derived from plants in the Scrophulariaceae family.

False Signup and view all the answers

What type of sugars can the glycone portion at position C-3 of cardiac glycosides contain?

mono, di, tri, or tetra saccharides Signup and view all the answers

The compounds containing a five-membered lactone ring are known as __________.

cardenolides Signup and view all the answers

Match the following components with their corresponding terms:

Cardenolides = Aglycones with 23 carbons Bufadienolides = Aglycones with 24 carbons Digitalis purpurea = Source of Digitoxin Strophanthus kombe = Source of K-strophanthoside Signup and view all the answers

What is a key medicinal compound derived from Digitalis purpurea?

Digitoxin Signup and view all the answers

Bufadienolides have a five-membered lactone ring.

False Signup and view all the answers

What enzyme do cardioactive glycosides primarily inhibit?

Na+/K+ ATPase Signup and view all the answers

The aglycone part of cardioactive glycosides is referred to as __________.

cardiac genin Signup and view all the answers

Which of the following statements correctly describes a feature of cardioactive glycosides?

They contain a β-OH group at position C-3. Signup and view all the answers

The average concentration of glycosides in Digitalis purpurea is around 0.16%.

True Signup and view all the answers

What is the main glycoside found in Strophanthus kombe?

K-strophanthoside Signup and view all the answers

Glycosides derived from Digitoxigenin include Lanatoside A, Acetyl-digitoxin, and __________.

Digitoxin Signup and view all the answers

Match the type of glycoside with the description:

Cardenolides = Contain a butenolide ring Bufadienolides = Contain a pentadienolide ring Aglycone with 23 carbons = Digitoxigenin Aglycone with 24 carbons = Scilladienolide Signup and view all the answers

What is the primary role of primary metabolites?

Support in growth and reproduction Signup and view all the answers

Secondary metabolites are primarily produced during the growth phase.

False Signup and view all the answers

What type of organism is known for producing erythromycin?

Streptomyces Signup and view all the answers

Atropine is derived from __________ and has important clinical uses.

various plants Signup and view all the answers

Which of the following is commonly used in food production?

Citric Acid Signup and view all the answers

Match the following secondary metabolites with their uses:

Erythromycin = Antibiotic treatment Atropine = Dilating pupils in eye exams Bacitracin = Topical anti-infection Pigments = Coloring agents in food Signup and view all the answers

Primary metabolites are typically produced during the stationary phase of growth.

False Signup and view all the answers

The significant amino acids like L-glutamate are produced from ________ species.

Corynebacteria Signup and view all the answers

Which of the following vitamins is classified as fat-soluble?

Vitamin A Signup and view all the answers

Water-soluble vitamins can be stored in the body.

False Signup and view all the answers

What is a primary function of Vitamin D in the body?

Assists in the absorption of calcium and phosphorus Signup and view all the answers

Vitamin A is essential for _______ and immune function.

vision Signup and view all the answers

Match the following vitamins with their primary deficiencies:

Vitamin A = Xerophthalmia Vitamin D = Rickets Vitamin C = Scurvy Vitamin K = Bleeding disorders Signup and view all the answers

Which of the following vitamins has a major form known as tocopherol?

Vitamin E Signup and view all the answers

Vitamin D3 is derived solely from plant sources.

False Signup and view all the answers

What is one common dietary source of Vitamin A?

Fish liver oils Signup and view all the answers

The two primary forms of Vitamin D are D2 (ergocalciferol) and D3 (_______).

cholecalciferol Signup and view all the answers

Match the following vitamin deficiencies with their conditions:

Vitamin A = Nyctalopia Vitamin D = Osteomalacia Vitamin C = Hyperkeratosis Vitamin K = Increased bleeding tendency Signup and view all the answers

Which vitamin can be converted to its active form from provitamin A substances?

Vitamin A Signup and view all the answers

Excessive intake of fat-soluble vitamins can lead to toxicity.

True Signup and view all the answers

What condition results from a deficiency of Vitamin D in children?

Rickets Signup and view all the answers

Vitamin E is essential for protecting _______ from oxidative damage.

cells Signup and view all the answers

Which of the following compounds is a precursor for the shikimic acid pathway?

Phosphoenol pyruvate Signup and view all the answers

What is the primary product formed during the light-dependent reactions of photosynthesis?

Oxygen Signup and view all the answers

The mevalonate pathway is responsible for synthesizing secondary metabolites in all organisms.

False Signup and view all the answers

Erythromycin is derived from Saccharopolyspora erythraea.

True Signup and view all the answers

Name one environmental stress that can trigger the expression of secondary metabolites.

Pathogens, herbivores attack, inappropriate pH, temperature changes, UV radiation, saline stress, or heavy metal stress. Signup and view all the answers

The pathway responsible for the synthesis of aromatic amino acids is known as the __________ pathway.

shikimic acid Signup and view all the answers

What role does chlorophyll play in photosynthesis?

Captures light energy Signup and view all the answers

The Calvin cycle primarily occurs in the ______ of the chloroplast.

stroma Signup and view all the answers

Match the following pathways with their primary product:

Shikimic Acid Pathway = Aromatic Amino Acids Malonate Pathway = Fatty Acids Mevalonate Pathway = Cholesterol Signup and view all the answers

Match the following processes of photosynthesis with their descriptors:

Light-dependent reactions = Convert light energy to chemical energy Calvin cycle = Convert carbon dioxide into glucose Glycolysis = Convert glucose into pyruvate Krebs cycle = Oxidize acetyl-CoA to produce ATP Signup and view all the answers

Which compound is a building block derived from acetyl-CoA?

Malonic acid Signup and view all the answers

What is the main carbon source for the dark reactions in photosynthesis?

Carbon dioxide Signup and view all the answers

Acetyl-CoA is a direct precursor for the growing fatty acid chain in fatty acid synthesis.

True Signup and view all the answers

What is the function of 5-enolpyruvylshikimate-3-phosphate synthase in the shikimic acid pathway?

Catalyzes the transformation of shikimate-3-phosphate and phosphoenolpyruvate. Signup and view all the answers

Bacitracin is commonly administered orally.

False Signup and view all the answers

Malonate is formed from acetyl-CoA by the addition of __________.

CO2 Signup and view all the answers

Name the enzyme that catalyzes the reaction in the Calvin cycle.

RuBisCO Signup and view all the answers

During glycolysis, glucose is converted to ______.

pyruvate Signup and view all the answers

Match the following building blocks with their derived sources:

C1 = S-methyl of L-methionine C2 = Acetyl-CoA C5 = Isoprene units C6-C3 = Phenylpropyl from phenylalanine Signup and view all the answers

Which enzyme catalyzes the ATP dependent phosphorylation of shikimate?

Shikimate kinase Signup and view all the answers

Match the following antibiotics with their descriptions:

Erythromycin = Wide antimicrobial spectrum antibiotic Bacitracin = Topical antibiotic from Bacillus subtilis Signup and view all the answers

What are the two types of photosystems involved in the light reactions?

Photosystem I and II Signup and view all the answers

The acetyl-CoA carboxylase enzyme is involved in the formation of malonyl-CoA.

True Signup and view all the answers

What type of secondary metabolites does the shikimic acid pathway specifically produce?

Phenolic compounds and alkaloids. Signup and view all the answers

The Krebs cycle occurs in the mitochondrial matrix.

True Signup and view all the answers

The main intermediates produced in the mevalonate pathway include __________ and its isomer.

Isopentenyl pyrophosphate Signup and view all the answers

What is the overall reaction for the Krebs cycle in relation to glucose?

C6H12O6 + 6CO2 + 38 ADP + 38 Pi → 6H2O + 6CO2 + 38 ATP Signup and view all the answers

Photosynthesis requires ______, water, and carbon dioxide.

light energy Signup and view all the answers

Which of the following is produced in the light-dependent reaction but not in the dark reaction of photosynthesis?

Oxygen Signup and view all the answers

All plants have chlorophyll b.

False Signup and view all the answers

Which vitamin plays a crucial role in blood clotting?

Vitamin K Signup and view all the answers

Vitamin E is primarily a water-soluble vitamin.

False Signup and view all the answers

What is a common deficiency symptom of Vitamin B1?

Wernicke encephalopathy Signup and view all the answers

Vitamin _______ is known for protecting cell membranes from oxidation.

E Signup and view all the answers

Match the following vitamins with their primary sources:

Vitamin B2 = Yeast Vitamin B3 = Meats Vitamin E = Plant oils Vitamin K = Green leafy vegetables Signup and view all the answers

Which vitamin is essential for the metabolism of bone proteins?

Vitamin K Signup and view all the answers

Riboflavin is sensitive to light and may change to lumichrome or lumiflavin when exposed.

True Signup and view all the answers

Name a deficiency condition associated with Vitamin B3.

Pellagra Signup and view all the answers

Thiamine deficiency can lead to ________, a syndrome affecting the nervous system.

beriberi Signup and view all the answers

Match the following vitamins with their primary functions:

Vitamin B1 = Energy metabolism Vitamin B2 = Coenzyme in oxidation-reduction reactions Vitamin B3 = Lowering LDL cholesterol Vitamin K = Blood clotting Signup and view all the answers

Which vitamin is vital for immune function boosting?

Vitamin E Signup and view all the answers

Vitamin K can be obtained from the intestinal microflora.

True Signup and view all the answers

What dietary sources are rich in Vitamin K?

Green leafy vegetables Signup and view all the answers

The primary use of Riboflavin (Vitamin B2) is as a _______ in energy metabolism.

coenzyme Signup and view all the answers

What is a primary use of ouabain (G-strophanthin)?

Cardiotonic for prompt therapeutic effect Signup and view all the answers

Oleander is considered non-toxic and can be safely consumed in any amounts.

False Signup and view all the answers

What two types of sugars make up the trisaccharide in strophanthidin?

cymarose, β-glucose and α-glucose Signup and view all the answers

The main constituent of Nerium oleander is ______.

oleanderin Signup and view all the answers

Match the following compounds to their uses:

Ouabain = Cardiotonic, administered I.V. Oleanderin = Potential anticancer treatment Red squill = Used as rat poison Squill glycosides = Expectorant with diuretic properties Signup and view all the answers

What is the primary purpose of treating plant material with lead acetate?

To precipitate tannins and non-glycosidal impurities Signup and view all the answers

Cardioactive glycosides exclusively contain a four-membered lactone ring.

False Signup and view all the answers

What are the two types of genin identified in cardioactive glycosides?

Cardenolides and bufadienolides Signup and view all the answers

The enzyme Na+/K+ ATPase is inhibited by cardioactive glycosides, leading to increased levels of __________ inside the cell.

Calcium ions Signup and view all the answers

Match the following cardiac glycosides with their sources:

Digitalis purpurea = Foxglove Strophanthus kombe = Dried ripe seeds Digitalis lanata = Dried leaves Digitalis glycosides = Various medicinal applications Signup and view all the answers

Which of the following structural features is NOT characteristic of cardioactive glycosides?

Lactone ring must be saturated Signup and view all the answers

The principal glycosides in Digitalis purpurea include digitoxin, gitoxin, and gitaloxin.

True Signup and view all the answers

Name one method used to purify crude glycosides.

Chromatography or crystallization Signup and view all the answers

Bufadienolides are condensation products involving a C21 steroid and a __________ unit.

C3 Signup and view all the answers

Which of the following is a function of cardioactive glycosides?

Increase cardiac muscle tone Signup and view all the answers

All cardioactive glycosides are derived from cholesterol.

False Signup and view all the answers

What configuration must be denoted when naming cardioactive glycosides?

The configuration of functional groups and whether they are α or β Signup and view all the answers

The glycone portion of cardiac glycosides can contain up to __________ monosaccharide molecules linked in series.

four Signup and view all the answers

What is one of the primary functions of pantothenic acid (Vitamin B5)?

Turn food into energy Signup and view all the answers

Which compound is associated with the dried leaves of Digitalis lanata?

Digitoxin Signup and view all the answers

Deficiency of Vitamin B6 can lead to peripheral neuropathy.

True Signup and view all the answers

What is a common dietary source of Vitamin B7?

Eggs Signup and view all the answers

Match the glycosides with their respective structural characteristics:

Cardenolides = Aglycones with 23 carbons Bufadienolides = Aglycones with 24 carbons Butenolide = 4 carbons attached to C17 Pentadienolide = 5 carbons with two double bonds Signup and view all the answers

Vitamin B9 is crucial during early pregnancy to reduce the risk of __________.

birth defects Signup and view all the answers

Match the following vitamins with their associated deficiencies:

Vitamin B5 = Fatigue and sleep disturbances Vitamin B6 = Peripheral neuropathy Vitamin B9 = Megaloblastic anemia Vitamin C = Scurvy Signup and view all the answers

Which vitamin is essential for the synthesis of red blood cells?

Vitamin B12 Signup and view all the answers

Vitamin C is the most stable of all vitamins.

False Signup and view all the answers

Which of the following is true regarding the structure of glycosides?

The glycone part generally confers solubility properties. Signup and view all the answers

List one function of Vitamin C.

Antioxidant activity Signup and view all the answers

Vitamin C helps in the synthesis of __________.

collagen Signup and view all the answers

β-glycosides are predominantly found in plants.

True Signup and view all the answers

What type of compound is a glycoside?

An organic compound Signup and view all the answers

What type of linkage connects the glycone and aglycone parts in glycosides?

Glycosidic linkage Signup and view all the answers

Glycosides derived from digitalis are primarily used as _______ agents.

cardiac Signup and view all the answers

Biotin is involved only in carbohydrate metabolism.

False Signup and view all the answers

Match each type of glycoside with its respective aglycone component:

Senna = O-glycoside Cascara = C-glycoside Black mustard = N-glycoside Saponin = S-glycoside Signup and view all the answers

What is one food source of Vitamin B12?

Beef liver Signup and view all the answers

Pyridoxine is the term usually used for __________ in pharmacy and medicine.

pyridoxol Signup and view all the answers

Which of the following is NOT a property of glycosides?

They are volatile and aromatic. Signup and view all the answers

Enzymatic hydrolysis of glycosides can only be carried out by one specific enzyme for all types of glycosides.

False Signup and view all the answers

Which of the following vitamins aids in the production of DNA and RNA?

Vitamin B9 Signup and view all the answers

Match the following vitamins with key roles:

Vitamin B5 = Energy metabolism Vitamin B6 = Neurotransmitter synthesis Vitamin B12 = DNA synthesis Vitamin C = Iron absorption Signup and view all the answers

Name a therapeutic class that glycosides can be derived from.

Cardiac drugs Signup and view all the answers

The hydroxyl group on the anomeric carbon is ______ in the α-form of glycosides.

down Signup and view all the answers

Match the glycoside with its corresponding feature:

Flavonoids = Yellow color Anthraquinones = Red or orange color Saponin = Odorless Rhubarb = Bitter taste Signup and view all the answers

Which of the following substances predominantly increases the water solubility of glycosides?

The sugar moiety Signup and view all the answers

Glycosides are relatively stable in alkaline conditions.

True Signup and view all the answers

What is the primary role of the aglycone part in glycosides?

Responsible for pharmacological activity Signup and view all the answers

The process by which plants inactivate hydrolyzing enzymes for glycosides involves putting them into _______ water or alcohol.

boiling Signup and view all the answers

What is a common primary metabolite produced by the organism Aspergillus niger?

Citric acid Signup and view all the answers

Secondary metabolites are primarily formed during the growth phase of an organism.

False Signup and view all the answers

Name one example of a primary metabolite used for large-scale production in industrial microbiology.

Ethanol Signup and view all the answers

___ is an example of a secondary metabolite with important clinical uses derived from various plants.

Atropine Signup and view all the answers

Match the following metabolites with their classifications:

Ethanol = Primary metabolite Erythromycin = Secondary metabolite Citric acid = Primary metabolite Bacitracin = Secondary metabolite Signup and view all the answers

Which of the following best describes a primary metabolite?

Organic compound involved in growth and reproduction. Signup and view all the answers

L-glutamate is an example of a secondary metabolite.

False Signup and view all the answers

What role do secondary metabolites play in ecological functions?

Defense mechanism, including serving as antibiotics. Signup and view all the answers

Which vitamin is essential for vision and immune function?

Vitamin A Signup and view all the answers

Water-soluble vitamins are stored in the body and can lead to toxicity if taken in excess.

False Signup and view all the answers

Name one condition that can result from Vitamin A deficiency.

nyctalopia Signup and view all the answers

Vitamin D3 is primarily obtained from _______ sources.

animal Signup and view all the answers

Match the following vitamins with their primary deficiency states:

Vitamin A = Xerophthalmia Vitamin D = Rickets Vitamin C = Scurvy Vitamin E = Neurological issues Signup and view all the answers

Which food is a natural source of Vitamin E?

Sunflower seeds Signup and view all the answers

Vitamin D3 is synthesized in the skin through exposure to UVB light.

True Signup and view all the answers

What are the two classes of vitamins?

Fat-soluble and water-soluble Signup and view all the answers

Vitamin _______ is critical for bone and calcium homeostasis.

D Signup and view all the answers

Which vitamin is also known as the 'sunshine vitamin'?

Vitamin D Signup and view all the answers

Excessive intake of fat-soluble vitamins is generally safe.

False Signup and view all the answers

List one dietary source of Vitamin C.

Oranges Signup and view all the answers

Vitamin K is important for _______ in blood clotting.

coagulation Signup and view all the answers

Match the vitamin with its natural source:

Vitamin A = Carrots Vitamin D3 = Oily fish Vitamin C = Berries Vitamin E = Nuts Signup and view all the answers

What process do plants use to capture light energy?

Photosynthesis Signup and view all the answers

Atropine is a competitive antagonist for nicotinic receptors.

False Signup and view all the answers

What is the main pigment involved in the light-dependent reactions of photosynthesis?

Chlorophyll-a Signup and view all the answers

The overall reaction of glycolysis converts glucose into ______.

pyruvate Signup and view all the answers

Match the following antibiotics with their source:

Erythromycin = Saccharopolyspora erythraea Bacitracin = Bacillus subtilis Signup and view all the answers

Which of the following substances is generated during the light-dependent reactions?

Oxygen Signup and view all the answers

The dark reaction of photosynthesis requires light to proceed.

False Signup and view all the answers

What are the two main stages of photosynthesis?

Light-dependent reaction and Light-independent reaction Signup and view all the answers

The Calvin cycle primarily occurs in the ______ of the chloroplast.

stroma Signup and view all the answers

Match the following stages of the Calvin cycle with their functions:

Carbon fixation = Formation of 3-PGA from RuBP and CO2 Reduction = Conversion of 3-PGA to G3P Regeneration = Restoration of RuBP from G3P Signup and view all the answers

What is the main product formed during the dark reactions of photosynthesis?

Glucose Signup and view all the answers

Photosystems are located in the cytosol of plant cells.

False Signup and view all the answers

What enzyme catalyzes the reaction in the carbon fixation stage of the Calvin cycle?

Rubisco Signup and view all the answers

During glycolysis, a net gain of ______ molecules of ATP is produced.

two Signup and view all the answers

What is the main function of the shikimic acid pathway?

Biosynthesis of phenolic compounds and aromatic amino acids Signup and view all the answers

The mevalonate pathway is crucial for cholesterol biosynthesis.

True Signup and view all the answers

What are the two starting substrates of the shikimic acid pathway?

Phosphoenol pyruvate and erythrose-4-phosphate Signup and view all the answers

C2 building blocks in biosynthesis are derived from __________.

acetyl-CoA Signup and view all the answers

Match the following metabolic pathways with their primary products:

Shikimic acid pathway = Aromatic amino acids Malonate pathway = Fatty acids Mevalonate pathway = Cholesterol and isoprenoids Acetate pathway = Acyl thioesters Signup and view all the answers

Which intermediate is produced from the mevalonate pathway?

Farnesyl pyrophosphate Signup and view all the answers

Environmental stresses do not affect the expression of secondary metabolites.

False Signup and view all the answers

What type of acid is malonate?

Three-carbon dicarboxylic acid Signup and view all the answers

The building blocks produced from photosynthesis are mainly used in __________.

biosynthesis of secondary metabolites Signup and view all the answers

Which of the following compounds is NOT derived from the shikimic acid pathway?

Cholesterol Signup and view all the answers

The acetate pathway directly synthesizes fatty acids.

True Signup and view all the answers

What are the main building blocks for secondary metabolite production categorized by carbon units?

C1, C2, C5, C6-C3 Signup and view all the answers

Match the following compounds with their carbon unit classification:

Acetyl-CoA = C2 S-methyl of L-methionine = C1 Isoprene units = C5 Phenylalanine = C6-C3 Signup and view all the answers

Which of the following describes the role of shikimic acid?

Intermediary in aromatic amino acid production Signup and view all the answers

Which of the following is a major dietary source of Vitamin E?

Wheat germ oil Signup and view all the answers

Vitamin K is primarily involved in energy metabolism.

False Signup and view all the answers

What are the symptoms of Vitamin B1 (thiamine) deficiency?

Wernicke encephalopathy and beriberi Signup and view all the answers

Vitamin ___ is essential for blood clotting.

K Signup and view all the answers

Match the following vitamins to their primary roles:

Vitamin E = Lipid-soluble antioxidant Vitamin K = Blood clotting Vitamin B3 = Energy transfer reactions Vitamin B1 = Nerve and muscle activity Signup and view all the answers

What is a common symptom of Vitamin E deficiency?

Muscle weakness Signup and view all the answers

Which of the following is a cardiotonic agent used intravenously?

Ouabin Signup and view all the answers

Alcohol can enhance the absorption of Vitamin B1.

False Signup and view all the answers

What are the three D's associated with niacin deficiency?

Dementia, dermatitis, diarrhea Signup and view all the answers

Oleander can be safely consumed in large amounts without toxicity.

False Signup and view all the answers

Vitamin B2 is also known as __________.

riboflavin Signup and view all the answers

What is the main constituent of Nerium oleander known for its medicinal use?

Oleanderin Signup and view all the answers

Match the B-vitamins with their sources:

B1 = Whole grains and legumes B2 = Dairy products and eggs B3 = Meats and fish B5 = Meats and whole grains Signup and view all the answers

Strophanthidin is coupled to a trisaccharide consisting of cymarose, β-glucose, and ______.

α-glucose Signup and view all the answers

Which vitamin contributes to the formation of myelin sheaths?

Vitamin B1 Signup and view all the answers

Match the following cardiac glycosides with their sources or uses:

Ouabin = S. grantus Oleanderin = Nerium oleander Red Squill = Urginea maritima Squill = Expectorant and diuretic Signup and view all the answers

Riboflavin is stable during cooking in the absence of light.

True Signup and view all the answers

Why is Vitamin K important for bone health?

It helps osteocalcin bind to minerals. Signup and view all the answers

Niacin is also referred to as __________.

Vitamin B3 Signup and view all the answers

Which of the following vitamins is known for its antihemorrhagic activity?

Vitamin K Signup and view all the answers

Vitamin E is primarily water-soluble.

False Signup and view all the answers

What is a primary source of pantothenic acid?

Cereal grains Signup and view all the answers

Vitamin B6 is necessary for amino acid metabolism.

True Signup and view all the answers

What deficiency can result from a lack of vitamin B9?

Megaloblastic anemia or macrocytic anemia Signup and view all the answers

Vitamin C is essential for the synthesis of ______.

collagen Signup and view all the answers

Match the following vitamins with their primary benefits:

Vitamin B5 = Helps in energy metabolism Vitamin B7 = Involved in fat metabolism Vitamin B12 = Prevents pernicious anemia Vitamin C = Antioxidant properties Signup and view all the answers

Which vitamin is essential for the production of red blood cells?

Vitamin B12 Signup and view all the answers

All types of glycosides yield the same number of sugars upon hydrolysis.

False Signup and view all the answers

Name a key deficiency symptom of vitamin C.

Scurvy Signup and view all the answers

Fatty acid synthesis requires the presence of ______.

biotin Signup and view all the answers

Match the vitamins with their primary food sources:

Vitamin B6 = Fish and poultry Vitamin B9 = Beans and whole grains Vitamin B5 = Animal organs Vitamin C = Citrus fruits Signup and view all the answers

What is a potential consequence of vitamin B12 deficiency?

Mood swings Signup and view all the answers

Pyridoxine is the primary form of vitamin B6 found in plant sources.

True Signup and view all the answers

List one role of biotin in the body.

Transfer of carbon dioxide in metabolism Signup and view all the answers

Vitamin B7 helps in the metabolism of ______.

carbohydrates Signup and view all the answers

What occurs during the purification of plant material from seeds?

Defatting or purification of the plant material Signup and view all the answers

Cardioactive glycosides have a specific action on cardiac muscle that increases excitability and contractility.

True Signup and view all the answers

What type of chemical structure is primarily associated with cardioactive glycosides?

Steroidal structure with lactone rings Signup and view all the answers

The main glycoside in both S. kombe and S. hispidus is known as __________.

K-strophanthoside Signup and view all the answers

Match the following glycosides with their corresponding characteristics:

Digitoxin = Derived from Digitalis purpurea K-strophanthoside = Main glycoside in S. kombe Bufotoxin = Derived from bufadienolides Scillarenin = Derived from scilladienolides Signup and view all the answers

What method is used to precipitate tannins during the purification process?

Treatment with lead acetate Signup and view all the answers

The glycone portion at position C-3 of cardiac glycosides may contain four monosaccharide molecules linked in series.

True Signup and view all the answers

What is the mechanism of action for cardioactive glycosides?

Inhibition of Na+/K+ ATPase enzyme Signup and view all the answers

Cardiac glycosides are proposed to arise from the condensation of a C21 steroid with a C2 unit, with bufadienolides arising from a C21 steroid and a __________ unit.

C3 Signup and view all the answers

Match the following digitalis glycosides with their derivatives:

Lanatoside A = Derived from Digitoxigenin Digitoxin = Derived from Digitoxigenin Gitaloxin = Derived from Digitoxigenin Gluco-gitaloxin = Derived from Digitoxigenin Signup and view all the answers

Which of the following correctly describes cardenolides?

Contain one double bond Signup and view all the answers

Bufadienolides contain a five-membered lactone ring.

False Signup and view all the answers

How many different glycosides have been identified in the leaves of Digitalis lanata?

Nearly 70 Signup and view all the answers

The presence of another β-OH group at C-14 is a characteristic feature of ______________.

cardioactive glycosides Signup and view all the answers

What is the primary difference between α and β glycosides?

The position of the hydroxyl group on the anomeric carbon Signup and view all the answers

Glycosides are always insoluble in water.

False Signup and view all the answers

Identify one therapeutic agent derived from glycosides.

Digitalis Signup and view all the answers

Glycosides can be hydrolyzed by heating with a dilute ______.

acid Signup and view all the answers

Match the type of glycosidic linkage with its corresponding type:

α-glycosides = Hydroxyl group down β-glycosides = Hydroxyl group up C-glycosides = Aglycone with carbon linkage O-glycosides = Aglycone with hydroxyl group linkage Signup and view all the answers

Which enzymes are primarily responsible for hydrolyzing β-glycoside linkages?

Emulsin Signup and view all the answers

The aglycone part of glycosides is responsible for solubility properties.

False Signup and view all the answers

What is one function of glycosides in plants?

Defense against microorganisms Signup and view all the answers

The sugar moiety in glycosides enhances ______ solubility.

water Signup and view all the answers

Match the glycoside with its corresponding source or type:

Senna = Laxative drug Glycyrrhizin = From saponins Frangula = Contains anthraquinones Digitalis = Cardiac glycoside Signup and view all the answers

What role do glycosides play in plant metabolism?

Waste products Signup and view all the answers

Most glycosides are volatile compounds.

False Signup and view all the answers

What is the effect of sugar residues on glycoside solubility?

Increase water solubility Signup and view all the answers

Glycosides can be classified depending on the chemical group of the ______.

aglycone Signup and view all the answers

Match the glycoside to its corresponding property:

Bitter taste = Most glycosides Colorless = General glycosides Yellow = Flavonoids Red or orange = Anthraquinones Signup and view all the answers

Study Notes

Metabolism

Metabolism is the chemical transformation that occurs in cells of living organisms.
Primary metabolites are involved in growth, development and reproduction.
Examples of primary metabolites include ethanol, lactic acid, and certain amino acids.
Secondary metabolites are derived from primary metabolites and are not directly involved in growth.
Examples of secondary metabolites include antibiotics like erythromycin and bacitracin.

Photosynthesis

Photosynthesis is the process that converts light energy into chemical energy stored in glucose.
Occurs in chloroplasts and other parts of green organisms.
Requires carbon dioxide, water and light energy.
Produces glucose and oxygen as byproducts.
Consists of two stages: light-dependent reaction and light-independent reaction.
Light reaction captures light energy and converts it into ATP and NADPH.
Dark reaction uses ATP and NADPH to convert carbon dioxide into glucose.

Glycolysis

The metabolic pathway that converts glucose into pyruvate.
Occurs in the cytosol and is oxygen-independent.
Produces ATP and pyruvate.

Citric Acid Cycle

Also known as the Krebs cycle or TCA cycle.
A series of enzyme-catalyzed reactions that occur in the mitochondrial matrix.
Oxidizes acetyl-CoA to form carbon dioxide and reduced coenzymes.
Generates ATP via the electron transport chain.

Biosynthesis of Secondary Metabolites

A multi-step process involving enzymes that convert substrates into more complex products.
Simple compounds are modified, converted, or joined together to form macromolecules.
Building blocks are derived from primary metabolites.
Important building blocks include acetyl CoA, shikimic acid, mevalonic acid, and malonic acid.

Shikimic-Acid Pathway

The basis for biosynthesis of phenolic compounds, alkaloids, and other aromatic compounds.
Occurs in chloroplast plant cells.
Triggered by environmental stresses like pathogens, herbivores, pH, temperature, UV radiation, and heavy metals.
Provides the building blocks for aromatic amino acids (phenylalanine, tyrosine, and tryptophan).

Malonic-Acid Pathway

Involved in the synthesis of fatty acids.
Uses acetyl CoA and malonyl CoA.
Malonyl CoA is formed from acetyl CoA by adding CO2.

Mevalonic-Acid Pathway

Synthesizes isoprenoid compounds.
Produces isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP).
IPP and DMAPP form the basic building blocks of isoprenoid compounds.
Leads to the production of cholesterol and other compounds like triterpenoids.

Introduction to Vitamins

Organic substances not synthesized within the body.
Essential in small amounts for normal metabolic functions.
Does not provide energy or building units for cellular structure.
Lack of specific vitamins lead to deficiency states like beriberi, rickets, scurvy, and xerophthalmia.

Classification of Vitamins

Fat-soluble vitamins: A, D, E, and K.
Water-soluble vitamins: C and B complex.

Fat-Soluble Vitamins

Stored in the body.
Deficiencies are rare; excessive intakes may be toxic.
Absorbed along with lipids.
Deficiency states can be caused by conditions that impair fat absorption.

Vitamin A

Also known as retinol.
Important for vision, growth development, immune function, red blood cell formation, skin and bone formation.
Deficiency leads to night blindness, xerophthalmia, hyperkeratosis, growth retardation, and decreased resistance to infection.

Vitamin D

Essential for calcium absorption and utilization.
Two forms: D2 (ergocalciferol) and D3 (cholecalciferol).
Vitamin D3 is formed in the skin by exposure to UVB radiation.
Vitamins D2 and D3 can be obtained from food or supplements.
Important for bone health, muscle function, immune system function, and cell function in general.
Deficiency leads to rickets in children and osteomalacia in adults.

Vitamin E

Refers to various forms of α-tocopherol.

Vitamin E

Several structurally related tocopherol analogs, including B, gamma, and S-tocopherols, occur in nature, but these substances possess only low levels of vitamin E activity.
Vitamin E is widely distributed in nature, and the body's requirements are normally satisfied by dietary sources.
Plant oils, green vegetables, whole grains, egg yolks, and meats are common dietary sources of this vitamin.
Wheat germ oil is a traditional natural source of vitamin E for therapeutic purposes.
Vitamin E is the major lipid-soluble antioxidant protecting cell membranes, proteins, and DNA from oxidation, thereby contributing to cellular health.
Vitamin E prevents oxidation of polyunsaturated fatty acids and lipids in the cells.
Vitamin E deficiency can cause nerve and muscle damage that results in loss of feeling in the arms and legs, loss of body movement control, muscle weakness, and vision problems.
A weakened immune system is another sign of vitamin E deficiency.

Vitamin K

Vitamin K is a term that refers to 2-methyl-1,4-naphthoquinone and derivatives of this compound.
Vitamin K is distributed widely in dairy products and many fruits and vegetables, green leafy vegetables being especially good dietary sources.
The intestinal microflora also provides a significant portion of the normal human supply of this vitamin.
Vitamin K acts primarily in blood clotting (antihemorrhagic activity).
Vitamin K is used in treatments for bleeding events caused by overdose of the anticoagulant drug warfarin.
Vitamin K helps in the metabolism of bone proteins (osteocalcin).
Without vitamin K, osteocalcin cannot bind to the minerals that normally form bones, resulting in poor bone mineralization.
Vitamin K helps regulate blood calcium levels.
Hemorrhage is the most common symptom in Vitamin K deficiency.

Vitamin B1

Thiamine or vitamin B1 has substituted pyrimidine and thiazole rings linked by a methylene bridge.
The vitamin is stable in an acidic environment but decomposes readily above pH 5.0.
It is estimated that about 50% of the vitamin in foods is destroyed during cooking.
Whole grains, legumes, and meats are good dietary sources of thiamine.
Alcohol inhibits its absorption from the small intestine.
Thiamin is a sulfur-containing vitamin that participates in energy metabolism.
Thiamin is involved in converting carbohydrates, lipids and proteins into energy.
It plays a key role in nerve and muscle activity.
Thiamin may be helpful to people with Alzheimer's disease.
Thiamin contributes to the development of myelin sheaths and improves brain function.
Vitamin B1 (thiamine) deficiency can cause several clinical syndromes, including Wernicke encephalopathy and beriberi.
Risk factors for deficiency include alcohol dependence, malabsorption, and a diet low in thiamine.

Vitamin B2

Riboflavin or vitamin B2 is a yellow, heat-stable substance that is slightly soluble in water.
Riboflavin is sensitive to light and will change into lumichrome or lumiflavin, depending on whether the irradiated solution is acidic or alkaline; neither lumichrome nor lumiflavin possesses physiologic activity.
Yeast is the richest natural source of riboflavin.
Dairy products, eggs, legumes, and meats are the main dietary sources of this vitamin.
Small amounts are provided by cereal grains, fruits, and green vegetables.
Riboflavin is stable during cooking in the absence of light.
Riboflavin occurs in foods in the free form and as riboflavin 5'-phosphate (Flavin mononucleotide or FMN) and flavin adenine dinucleotide (FAD).
The nucleotides are hydrolyzed to riboflavin in the upper gastrointestinal tract.
Free riboflavin is absorbed readily into cells of the intestinal mucosa by an active transport system that is enhanced by bile salt.
Riboflavin functions as a coenzyme in numerous oxidation-reduction reactions, which are necessary for releasing energy from carbohydrates, fats and proteins.
Riboflavin stimulates growth and reproduction.
It plays a role in vision.
Riboflavin plays a role in the conversion of vitamins B6, folic acid, and niacin into their active coenzyme forms.
Riboflavin neutralizes free radicals hence acts as an antioxidant.
Riboflavin deficiency can cause stomatitis and dermatitis.

Vitamin B3

Niacin, nicotinic acid, or vitamin B3 is a simple, naturally occurring pyridine derivative that prevents pellagra.
Niacinamide or nicotinamide also occurs naturally, has antipellagra activity, and is used for dietary and therapeutic purposes.
Niacin and niacinamide are readily absorbed from the gastrointestinal tract under normal circumstances.
Meats, fish, and dairy products are good dietary sources of niacin.
The roasting of coffee beans results in the release of a significant quantity of niacin as well as the development of a characteristic flavor.
Tryptophan is also converted to niacin in the body.
Niacin acts as a coenzyme in energy-transfer reactions.
Niacin is similar to the riboflavin coenzymes in that it carries hydrogen during metabolic reactions.
Niacin protects against neurological degeneration and Alzheimer’s disease.
Niacin helps lower LDL cholesterol.
Niacin lowers the risk of cardiovascular diseases and eases arthritis.
Pellagra is the classic niacin-deficiency condition.
Symptoms of deficiency involve the nervous system, the skin, and the gastrointestinal tract and are sometimes summarized as the 3D's—dementia, dermatitis, and diarrhea.
Oral lesions, especially angular stomatitis and a red tongue, are more distinctive than the other symptoms.

Vitamin B5

Pantothenic acid or vitamin B5 is a component of the vitamin B complex that is sometimes known as the “chick antidermatitis factor” (based on a prior bioassay procedure).
Pantothenic acid is a naturally occurring compound that upon hydrolysis yields β-alanine and pantoic acid, a substituted butyric acid derivative.
Animal organs (heart, kidney, and liver) and cereal grains are rich dietary sources of pantothenic acid.
Pantothenic acid helps to turn food into energy.
It is involved in the synthesis of lipids, neurotransmitters, steroid hormones, and hemoglobin.
Pantothenic acid aids in maintenance and repair of tissues and cells of the skin and hair.
It helps in the healing of wounds and lesions.
Pantothenic acid normalizes the blood lipid profile.
Pantothenic acid deficiency can cause fatigue and sleep disturbances.

Vitamin B6

Vitamin B6 is a term that is applied to pyridoxol, pyridoxal, and pyridoxamine, three closely related, naturally occurring, highly substituted pyridine derivatives with comparable physiologic activity.
Pyridoxine, the most stable of these substances, is synthesized for exogenous dietary supplementation and therapeutic purposes.
Beef liver, tuna, salmon, fortified cereals, chickpeas, poultry, and some vegetables and fruits are good sources of vitamin B6.
Vitamin B6 improves mood.
It is required for biological reactions including amino acid metabolism, neurotransmitter synthesis, and red blood cell formation.
Vitamin B6 acts as a critical cofactor for a diverse range of biochemical reactions that regulate basic cellular metabolism.
Vitamin B6 deficiency can cause peripheral neuropathy.
Symptoms of vitamin B6 deficiency somewhat resemble those of niacin and riboflavin deficiencies, including neurological abnormalities, skin lesions, and hypochromic microcytic anemia.

Vitamin B7

Foods that contain the most biotin include eggs, fish, meat, seeds, nuts, and certain vegetables (such as sweet potatoes).
Biotin plays an important role in metabolism as a coenzyme that transfers carbon dioxide.
This role is critical in the breakdown of food (carbohydrates, fats and proteins) into energy.
Biotin is involved in many cellular reactions, particularly in fat and protein metabolism of hair roots, finger nails, and skin.
It is used in fatty acid synthesis.
Biotin deficiency can cause fatigue, depression and dermatitis.

Vitamin B9

Folic acid, folacin, pteroylglutamic acid, and occasionally vitamin B9 are terms that refer to a material with anti-anemia properties.
Beans, peanuts, sunflower seeds, fresh fruits, fruit juices, whole grains, and liver are good sources of folic acid.
Folate is essential for brain development and function.
Folate aids in the production of DNA and RNA.
It plays a role in the metabolism of vitamins and amino acids.
Folate is crucial during early pregnancy to reduce the risk of birth defects of the brain and spine.
Folate is required for the synthesis of glycine, methionine, nucleotides T & U.
Deficiency causes megaloblastic and macrocytic anemias and glossitis.

Vitamin B12

Vitamin B12 (cobalamins) are terms that refer to a series of porphyrin-related corrinoid derivatives that function as extrinsic factors to prevent pernicious anemia.
Cyanocobalamin, a red crystalline material, is the most stable of the cobalamins and is frequently utilized in therapy.
Hydroxocobalamin, in which the cyano group is replaced with a hydroxyl substituent, is also used therapeutically.
Vitamin B12 acts as a coenzyme in the conversion of homocysteine to methionine.
It plays a role in the metabolism of fatty acids and amino acids.
Vitamin B12 contributes to the production of neurotransmitters.
Vitamin B12 maintains a special lining that surrounds and protects nerve fibers.
Bone cell activity depends on vitamin B12.
Vitamin B12 plays a significant role in DNA synthesis.
It helps in brain function and the synthesis of red blood cells.
Deficiencies usually involve rapidly dividing cells of the hematopoietic system (e.g., megaloblastic anemia) and irreversible neurological damage (e.g., defective myelin nerve sheaths).
Symptoms include irritability, weakness, memory loss, mood swings, and a sensation of tingling or numbness of the arms and legs.

Vitamin C

Vitamin C or L-ascorbic acid is a naturally occurring vitamin substance that prevents scurvy and has useful antioxidant properties.
It occurs in equilibrium with dehydro-L-ascorbic acid, an oxidized form, which also has antiscorbutic properties.
Vitamin C is the least stable of all the vitamins.
Good dietary sources of ascorbic acid include citrus fruits, tomatoes, strawberries, and other fresh fruits and vegetables.
Although vitamin C content is preserved on freezing, up to 50% of the vitamin C content is lost upon cooking.
One of the important properties of Vitamin C is its antioxidant activity.
Vitamin C functions in enzyme activation and oxidative stress reduction.
It plays roles in the synthesis of collagen and absorption of iron.
Vitamin C aids defense against infections and inflammation.
Vitamin C helps to prevent certain diseases such as cancer, the common cold, cardiovascular diseases, and cataracts.
Vitamin C deficiency causes scurvy.

Glycosides

A glycoside is an organic compound, usually of plant origin, that is composed of a sugar portion linked to a non-sugar moiety by a glycosidic bond.
The sugar portion is called the glycon.
The non-sugar portion is called the aglycon or genin.
There are four basic classes of glycosides: C-glycosides, in which the sugar is attached to the aglycone through a C-C bond, and O-glycosides in which the sugar is connected to the aglycone through a oxygen-carbon bond, S-glycosides, and N-glycosides.
Glycosides yield one or more sugars among the products upon enzymatic or acid hydrolysis.
The sugar component of glycosides may be mono-, di-, tri- or tetrasaccharides.
Sugars in glycosides exist in isomeric α and β forms so both α and β glycosides are theoretically possible, but the β-form is the one that occurs in plants.
The two diastereoisomers differ in configuration about the anomeric carbon (C-1).
The hydroxyl group on the anomeric carbon is down in relation to the cyclic structure for the α anomer while the hydroxyl group on the anomeric carbon is up in relation to the cyclic structure for the β anomer.
Chemically the glycosides are acetals in which the hydroxyl group (OH) of the glycone is condensed with the hydroxyl group of the aglycone.
Sugars exist predominantly as cyclic hemiacetals (R-O-C-OH group), while glycosides are usually mixed acetals (R-O-C-O-R) group.
Inside the body, glycosides will be cleaved to glycone and aglycone parts.
The glycone part confers on the molecule solubility properties, thus is important in the absorption and distribution in the body.
The aglycone part is responsible for the pharmacological activity.

Physical and Chemical Properties of Glycosides

Because of the complexity of the structure of naturally occurring glycosides, no generalizations are possible with regard to their stability.
There are differences in their solubility properties.
Most glycosides are soluble in water or hydroalcoholic solutions and insoluble or less soluble in non-polar organic solvents because the solubility properties of the sugar residues exert a considerable effect; i.e. the sugar moiety increases water solubility.
The aglycon part is soluble in non-polar (organic) solvents such as benzene, ether, and chloroform.
Glycosides can be hydrolyzed by heating with a dilute acid where by the glycosidic linkages are cleaved.
Glycosides are relatively stable towards alkalis.
Glycosides can be hydrolyzed by appropriate enzymes, which are usually found in the same plant, in separate compartments.
There is a specific enzyme for each glycoside to exert a hydrolytic action on it.
The same enzyme is capable to hydrolyze different glycosides, but α and β stereo-isomers of the same glycoside are usually not hydrolyzed by the same enzyme.
Emulsin is found to hydrolyze most β-glycoside linkages while maltase and invertase are α-glycosidases, capable of hydrolyzing.
Glycosides are solid, amorphous and non-volatile.
Glycosides are colorless except flavonoids which are yellow and anthraquinones which are red or orange.
Most glycosides have a bitter taste.
Glycosides are odorless except saponin (glycyrrhizin).

Importance of Glycosides

Glycosides play an important role in the life of the plant and are involved in different functions:
Sugar reserves.
Waste products of plant metabolism.
Mean of detoxification.
Regulating osmosis.
Regulating the supply of substances of importance in metabolism.
Defense against the invasion of tissues by microorganisms.
Many therapeutic agents are derived from glycosides.
Some of our most valuable cardiac glycosides are from digitalis, strophanthus, squill, and others.
Laxative drugs, such as senna, aloe, rhubarb, cascara sagrada, and frangula, contain emodin and other anthraquinone glycosides.
Sinigrin, a glycoside from black mustard, yields allyl isothiocyanate, a powerful local irritant.

Classification of Glycosides

Glycosides can be classified according to the following:
The type of glycosidic linkage (α-glycosides or β-glycosides).
The chemical group of the aglycon involved in the formation of glycoside linkage (O-glycosides, C-glycosides, S-glycosides, and N-glycosides).
The chemical nature of the aglycon (cardioactive group, anthraquinone group, saponin group, cyanophore group, isothiocyanate group, flavonol group, alcohol group, aldehyde group, phenol group).
The nature of the simple sugar component of the glycoside (glucoside, galactoside, mannoside, arabinoside).

Biosynthesis of Glycosides

Biosynthetic pathways are widely variable depending on the type of aglycone as well as the glycone units.
The aglycone and the sugar parts are biosynthesized separately, and then coupled to form a glycoside.
The coupling of the two parts occurs via phosphorylation of a sugar to yield a sugar 1-phosphate which reacts with a uridine triphosphate to form a uridine diphosphate sugar (UDP-sugar) and inorganic phosphate.
This UDP-sugar reacts with the aglycone to form the glycoside and a free UDP.

Extraction of Glycosides

Since glycosides are accompanied by specific hydrolyzing enzymes, these enzymes must be inactivated by putting the plant in boiling water or alcohol.
Defatting or purification of the plant material in case of seeds.
Treatment with lead acetate to precipitate tannins and other non-glycosidal impurities.
Removal of any excess of lead acetate by passing hydrogen sulfide H2S gas through the solution.
The extract is filtered and concentrated to get the crude glycoside.
Purification of the crude glycosides by chromatography or crystallization.

Cardioactive Glycosides

The glycosides of this group are characterized by their highly specific action on cardiac muscle, increasing tone, excitability, and contractility.
The aglycones of these glycosides are referred to as "cardiac genin".
They are steroidal in nature, specifically, they are derivatives of cyclopentaphenanthrene containing an unsaturated lactone ring attached to C17.
Two types of genin may be distinguished according to whether there is a five- or six-membered lactone ring.
These types are known respectively as cardenolides (e.g., digitoxigenin) and bufanolides or bufadienolides (e.g., scillarenin).
In the cardenolide (aglycones with 23 carbons), the lactone ring attached at C17 is a butenolide (4 carbons), which is also referred as α,β-unsaturated lactone ring. (e.g., the glycosides of digitalis and strophanthus species).
The lactone ring attached at C17 in the scilladienolide (aglycone with 24 carbons) is a pentadienolide (5 carbons with two double bonds), also called a pentenolide. (e.g. the squill glycosides and, Bufotoxin).

Bufadienolides

Bufadienolides are a group of cardiac glycosides, which are naturally occurring compounds that affect the heart.
They are characterized by their specific chemical structure, including a 6-membered doubly unsaturated lactone ring at position C-17 and at least one double bond in the steroid nucleus.
They are found in plants like squill bulbs (Urginea maritima), which are used medicinally for their expectorant, emetic, cardiotonic, and diuretic properties.
Bufadienolides are often used as rat poison due to their toxic effects.

Cardioactive Glycosides

These are a class of natural compounds found in plants that exert a strong effect on the heart.
They are characterized by the presence of a specific structure: a β-OH group at positions C-3 and C-14, an unsaturated 5 or 6-membered lactone ring at position C-17, and additional OH groups at positions C-5, C-11, and C-16.
They are classified into different types based on the number of double bonds present: cardenolides (one double bond), dienolides (two double bonds), cardanolides (no double bond), and bufanolides (no double bond).

Digitalis

Digitalis is a dried leaf of the plant Digitalis purpurea (Foxglove).
It contains a large number of cardiac glycosides, with the most important ones being digitoxin, gitoxin, and gitaloxin.
Digitalis has been used in the treatment of congestive heart failure.

Strophanthus

Strophanthus is a dried ripe seed of the plant Strophanthus kombe or Strophanthus hispidus.
It contains cardiac glycosides, particularly K-strophanthoside, K-strophanthin-B, and cymarin.
Strophanthus is used intravenously (I.V.) as a cardiotonic agent.

Oleander

Oleander is derived from the plant Nerium oleander.
It contains cardiac glycosides, especially oleanderin, which is considered a promising agent for anticancer treatment.
Oleander is known to be poisonous, particularly to animals, if consumed in large quantities.

Squill

Squill refers to the bulb of the plant Urginea maritima (white or Mediterranean squill) or Urginea indica (Indian squill).
Squill glycosides differ from cardenolides in having a six-membered doubly unsaturated lactone ring at position C-17 and at least one double bond in the steroid nucleus.
Squill is used as an expectorant, but it also possesses emetic, cardiotonic, and diuretic properties.
Red squill, derived from the bulb of the red variety of Urginea maritima, is used as a rat poison.

Mechanism of Action

Cardioactive glycosides inhibit the Na+/K+ ATPase enzyme, a membrane-bound enzyme responsible for maintaining potassium (K+) levels inside the cell and sodium (Na+) levels outside the cell.
Inhibition of this enzyme disrupts ion balance, leading to increased calcium (Ca+2) entry into the cell.
Increased intracellular calcium promotes the contraction of actin and myosin, leading to stronger heart contractions.

Important Facts

The glycone portion of cardiac glycosides can contain up to four monosaccharide molecules linked in series.
Cardioactive glycosides are primarily derived from mevalonic acid, with the final molecules arising from a condensation of a C21 steroid with a C2 or C3 unit.
Digitalis (foxglove) contains numerous cardiac glycosides, including digitoxin, gitoxin, and gitaloxin.
Strophanthus contains K-strophanthoside, K-strophanthin-B, and cymarin, which are based on the genin strophanthidin.
Oleander contains oleanderin, a potential anticancer agent.
Squill glycosides differ from cardenolides in their structure and have expectorant, emetic, cardiotonic, and diuretic properties.

Metabolism

Metabolism refers to all chemical processes in living organisms.
Metabolites are products of metabolic processes and include primary and secondary metabolites.
Primary metabolites are involved in essential functions during growth, development, and reproduction, like energy metabolism, while secondary metabolites don't have a central role and are often produced during the stationary phase of growth.

Primary Metabolites

Primary metabolites include ethanol, lactic acid, and certain amino acids.
Primary metabolites like amino acids (L-glutamate, L-lysine) and citric acid are commonly used in industrial microbiology.
L-glutamate and L-lysine are produced by Corynebacteria glutamicum, while citric acid is produced by Aspergillus niger.

Secondary Metabolites

Secondary metabolites are formed by modifying primary metabolite synthases and often serve ecological functions, like defense mechanisms, by producing antibiotics and pigments.
Atropine, erythromycin, and bacitracin are examples of secondary metabolites used industrially.
Atropine, derived from plants, is a muscarinic acetylcholine receptor antagonist used to treat bradycardia.
Erythromycin, produced by Saccharopolyspora erythraea, is a broad-spectrum antibiotic commonly administered orally.
Bacitracin, produced by Bacillus subtilis, is a topical antibiotic.

Photosynthesis

Photosynthesis converts light energy into chemical energy stored in glucose.
The process occurs in chloroplasts of green organisms.
Photosynthesis depends on carbon dioxide, water, and light energy, producing glucose, oxygen, and water.
Pigments like chlorophyll a, chlorophyll b, and carotenoids are involved in capturing light energy, with chlorophyll a as the main pigment.

Light Reaction

This reaction uses light energy to generate ATP and NADPH in the thylakoid membranes of chloroplasts.
Photosystems I and II, within the grana, gather light and play a key role in the light-dependent reactions.

Dark Reaction

This reaction is also called the carbon-fixing reaction and is light-independent.
It occurs in the stroma of the chloroplast, using NADPH and ATP from the light reaction to synthesize sugar molecules.
The Calvin cycle is a crucial part of the dark reaction, incorporating carbon dioxide from the atmosphere to form glucose.

Glycolysis

This pathway converts glucose into pyruvate in the cytosol with a net gain of two ATP molecules.
This process can occur in both aerobic and anaerobic conditions.

Citric Acid Cycle

This cycle takes place in the mitochondrial matrix and oxidizes acetyl-CoA to carbon dioxide, producing reduced coenzymes that generate ATP in the electron transport chain.

Biosynthesis of Secondary Metabolites

Biosynthesis involves multi-step enzyme-catalyzed processes, converting substrates into more complex products using primary metabolites as building blocks.
Important building blocks include acetyl CoA, shikimic acid, mevalonic acid, and malonic acid, derived from photosynthesis, glycolysis, and the Krebs cycle.

Shikimic Acid Pathway

This pathway is essential for the biosynthesis of phenolic compounds, alkaloids, and other aromatic compounds.
It occurs in chloroplasts of plant cells and involves phenylpropanoid precursors.
It is a seven-step pathway used by bacteria, archaea, fungi, algae, some protozoans, and plants for the synthesis of folates and aromatic amino acids (phenylalanine, tyrosine, and tryptophan).

Malonic Acid Pathway

This pathway works with acyl carrier protein (ACP) to produce fatty acyl thioesters of ACP, which are important intermediates in fatty acid synthesis.
Acetyl CoA units are used to synthesize fatty acids of varying chain lengths.

Mevalonic Acid Pathway

This pathway is also known as the isoprenoid pathway and is involved in the synthesis of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR).
The pathway is crucial for cholesterol biosynthesis, protein synthesis, membrane cell structure, steroid hormone production, and other functions.
The pathway produces isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are important building blocks for isoprenoid compounds.

Vitamin E

Several tocopherol analogs, including B, y, and S-tocopherols, exist in nature, but possess low levels of vitamin E activity.
Vitamin E is widely distributed in nature, and dietary sources typically meet the body's requirements.
Plant oils, green vegetables, whole grains, egg yolks, and meats are common dietary sources.
Wheat germ oil is a traditional natural source of vitamin E for therapeutic purposes.
Vitamin E is the major lipid-soluble antioxidant, protecting cell membranes, proteins, and DNA from oxidation.
Vitamin E prevents oxidation of polyunsaturated fatty acids and lipids in cells.
Vitamin E deficiency can lead to nerve and muscle damage resulting in loss of feeling in extremities, movement control, muscle weakness, and vision problems.
A weakened immune system is another sign of deficiency.

Vitamin K

Vitamin K refers to 2-methyl-1,4-naphthoquinone and its derivatives.
Dairy products, various fruits and vegetables, and green leafy vegetables are good sources of vitamin K.
The intestinal microflora also provide a significant portion of the normal human supply of vitamin K.
Vitamin K's primary function is in blood clotting (antihemorrhagic activity).
Vitamin K is used in treatments for bleeding events caused by warfarin overdose.
Vitamin K assists in metabolism of bone proteins (osteocalcin), crucial for bone mineralization.
Vitamin K deficiency leads to hemorrhage, the most common symptom.

Water-Soluble Vitamins

Water-soluble vitamins are a group of essential nutrients that dissolve in water.

B-complex Vitamins

These vitamins are a group of eight essential nutrients involved in various metabolic processes.

Vitamin B1 (Thiamine)

Thiamine contains substituted pyrimidine and thiazole rings linked by a methylene bridge.
Commercial thiamine is prepared by chemical synthesis and is usually used as the hydrochloride salt.
Thiamine is stable in acidic environments but decomposes readily above pH 5.0.
About 50% of thiamine in food is destroyed during cooking.
Whole grains, legumes, and meats are good sources of thiamine.
Alcohol inhibits thiamine absorption.
Thiamine is involved in energy metabolism, converting carbohydrates, lipids, and proteins into energy.
Plays a key role in nerve and muscle activity.
May be helpful for people with Alzheimer's disease.
Involved in development of myelin sheaths and improves brain function.
Deficiency can cause Wernicke encephalopathy and beriberi.
Risk factors include alcohol dependence, malabsorption, and a thiamine-deficient diet.

Vitamin B2 (Riboflavin)

Riboflavin is a yellow, heat-stable substance slightly soluble in water. It is sensitive to light.
Yeast is the richest natural source of riboflavin.
Dairy products, eggs, legumes, and meats are the main dietary sources.
Riboflavin is stable during cooking in the absence of light.
Riboflavin exists in foods as free form or as riboflavin 5'-phosphate (FMN) and flavin adenine dinucleotide (FAD).
These nucleotides are hydrolyzed to free riboflavin in the upper gastrointestinal tract.
Free riboflavin is readily absorbed into cells by an active transport system enhanced by bile salts.
Riboflavin acts as a coenzyme in numerous oxidation-reduction reactions, essential for energy release from carbohydrates, fats, and proteins.
It stimulates growth and reproduction.
Plays a role in vision.
Involved in conversion of vitamins B6, folic acid, and niacin into their active coenzyme forms.
Acts as an antioxidant by neutralizing free radicals.
Deficiency causes stomatitis and dermatitis.

Vitamin B3 (Niacin)

Niacin, nicotinic acid, or vitamin B3 is a naturally occurring pyridine derivative that prevents pellagra.
Niacinamide or nicotinamide also occurs naturally and has anti-pellagra activity, being used for dietary and therapeutic purposes.
They are readily absorbed from the gastrointestinal tract under normal circumstances.
Meats, fish, and dairy products are good dietary sources of niacin.
Roasting coffee beans releases significant amounts of niacin.
Tryptophan can be converted to niacin in the body.
Niacin acts as a coenzyme in energy-transfer reactions.
Similar to riboflavin coenzymes, it carries hydrogen during metabolic reactions.
Protects against neurological degeneration and Alzheimer's disease.
Helps lower LDL cholesterol.
Lowers cardiovascular disease risk and eases arthritis.
Deficiency causes pellagra, characterized by symptoms affecting the nervous system, skin, and gastrointestinal tract (dementia, dermatitis, and diarrhea).

Vitamin B5 (Pantothenic acid)

Pantothenic acid is a component of the vitamin B complex, sometimes known as the "chick antidermatitis factor."
Hydrolysis of pantothenic acid yields β-alanine and pantoic acid.
Animal organs (heart, kidney, and liver) and cereal grains are rich dietary sources of pantothenic acid.
Pantothenic acid facilitates the conversion of food into energy.
Involved in the synthesis of lipids, neurotransmitters, steroid hormones, and hemoglobin.
Maintains and repairs tissues and cells of the skin and hair.
Helps heal wounds and lesions.
Normalizes blood lipid profiles.
Deficiency causes fatigue and sleep disturbances.

Vitamin B6 (Pyridoxine)

Vitamin B6 refers to pyridoxol, pyridoxal, and pyridoxamine, three related pyridine derivatives with comparable physiological activity.
Pyridoxine is the predominant form of vitamin B6 in plants, while pyridoxal and pyridoxamine occur in animal tissues.
Synthetically prepared pyridoxine is typically used for dietary supplementation.
Beef liver, tuna, salmon, fortified cereals, chickpeas, poultry, and some vegetables and fruits are good sources of Vitamin B6.
Vitamin B6 is required for biological reactions, including amino acid metabolism, neurotransmitter synthesis, and red blood cell formation.
Acts as a coenzyme for biochemical reactions regulating cellular metabolism.

Vitamin B7 (Biotin)

Foods rich in biotin include eggs, fish, meat, seeds, nuts, and vegetables like sweet potatoes.
Biotin plays a crucial role in metabolism as a coenzyme that transfers carbon dioxide.
Essential for the breakdown of food (carbohydrates, fats, and proteins) into energy.
Involved in numerous cellular reactions, particularly fat and protein metabolism of hair, nails, and skin.
Used in fatty acid synthesis.
Deficiency causes fatigue, depression, and dermatitis.

Vitamin B9 (Folic Acid)

Folic acid, folacin, pteroylglutamic acid, and vitamin B9 are terms referencing a material with anti-anemia properties.
Beans, peanuts, sunflower seeds, fresh fruits, fruit juices, whole grains, and liver are good sources of folic acid.
Folic acid is essential for brain development and function.
Aids in the production of DNA and RNA.
Involved in the metabolism of vitamins and amino acids.
Crucial during early pregnancy to reduce the risk of birth defects.
Required for the synthesis glycine, methionine, and nucleotides T and U.
Deficiency causes megaloblastic and macrocytic anemias and glossitis.

Vitamin B12 (Cobalamin)

Vitamin B12 (cobalamins) are a series of porphyrin-related corrinoid derivatives that function as extrinsic factors preventing pernicious anemia.
Cyanocobalamin is the most stable cobalamin, commonly used therapeutically.
Hydroxocobalamin, with a hydroxyl group replacing the cyano group, is also used therapeutically.
Vitamin B12 acts as a coenzyme in the conversion of homocysteine to methionine.
It plays a role in the metabolism of fatty acids and amino acids.
Involved in the production of neurotransmitters.
Maintains the lining surrounding and protecting nerve fibers.
Bone cell activity depends on vitamin B12.
Plays a significant role in DNA synthesis.
Essential for brain function and red blood cell synthesis.
Deficiency affects rapidly dividing cells in the hematopoietic system (e.g., megaloblastic anemia) and can cause irreversible neurological damage (e.g., defective myelin nerve sheaths).

Vitamin C

Vitamin C, or L-ascorbic acid, prevents scurvy and has antioxidant properties.
It exists in equilibrium with dehydro-L-ascorbic acid, an oxidized form with antiscorbutic properties.
Vitamin C is the least stable of all vitamins.
Citrus fruits, tomatoes, strawberries, and other fresh fruits and vegetables are good dietary sources.
Freezing preserves the vitamin content, but cooking can lead to a 50% loss of vitamin C.
Vitamin C has significant antioxidant activity.
Functions in enzyme activation and oxidative stress reduction.
Plays a role in collagen synthesis and iron absorption.
Important for defense against infections and inflammation.
Helps prevent diseases like cancer, the common cold, cardiovascular diseases, and cataracts.
Deficiency causes scurvy.

Bufadienolides

Bufadienolides are a type of cardiac glycoside with a six-membered doubly unsaturated lactone ring at position C-17
They have at least one double bond in the steroid nucleus
Squill glycosides (R1=OH, R2=H) and Bufotoxin (R1 & R2 = ester group) are examples of bufadienolides

Cardiac Glycosides

All cardioactive glycosides have a β-OH group at position C-3, which is involved in a glycosidic linkage to a mono, di, tri, or tetrasaccharide
They also have a β-OH group at C-14
They have an unsaturated 5 or 6-membered lactone ring at position C-17, also in the β configuration
They may have additional OH groups at C-5, C-11, and C-16

Nomenclature

The sequence of nomenclature for cardioactive glycosides is as follows:
- Arrange the functional groups and denote their configuration
- Denote whether the configuration is α or β
- Denote the type of glycoside
- Denote the position of the double bonds
If the compound has one double bond, it is called a cardenolide
If it has two double bonds, it is called a dienolide
If it has no double bond, it is called a cardanolide or bufanolide

Biosynthesis

Aglycones of cardiac glycosides are derived from mevalonic acid
The final molecules arise from a condensation of a C21 steroid with a C2 unit (the source of C-22 and C-23).
Bufadienolides are condensation products of a C21 steroid and a C3 unit

Drugs containing cardioactive glycosides

Digitalis or foxglove
- It's the dried leaf of Digitalis purpurea (Scrophulariaceae)
- Contains a large number of glycosides, the most important being digitoxin, gitoxin, and gitaloxin
- The average concentration of glycosides in the leaf is about 0.16%
- Nearly 30 other glycosides have been identified in the drug, including purpurea glycosides A and B, gluco-gitaloxin, and gluco-digitoxigenin
- Primary glycosides with acetylated sugar moieties
Digitalis lanata
- Nearly 70 different glycosides have been detected in the leaves of Digitalis lanata
- All are derivatives of five different aglycones, three of which (digitoxigenin, gitoxigenin, and gitaloxigenin) also occur in Digitalis purpurea
- The other two types of glycosides are derived from digoxigenin and diginatigenin, which occur in Digitalis lanata but not in Digitalis purpurea
- The leaves of Digitalis lanata are used as a source of the glycosides digoxin and lanatoside C
- Lantoside A, B, and E are acetyl derivatives of purpurea A, B, and E, respectively
Glycosides derived from Digitoxigenin:
- Lanatoside A = Digitoxigenin---DX---DX----DX(AC)---G
- Acetyl-digitoxin = Digitoxigenin---DX---DX----DX---(AC)
- Digitoxin = Digitoxigenin------DX---DX----DX
- Purpurea gly A = Digitoxigenin---DX---DX----DX---G
- DX = Digitoxose, DX (AC)=Acetyldigitoxose, G = Glucose
Strophanthus
- It's the dried ripe seeds of Strophanthus kombe or Strophanthus hispidus (Apocyanaceae)
- Principal glycosides are K-strophanthoside, K-strophanthin-B, and cymarin, all based on the genin strophanthidin
- K-strophanthoside, also known as strophoside, is the main glycoside in both S.kombe and S.hispidus
- It's composed of the genin strophanthidin coupled to a trisaccharide consisting of cymarose, β-glucose, and α-glucose
- Strophanthin is used intravenously as a cardiotonic
Ouabin (G-strophanthin)
- It's obtained from Strophanthus gratus (Apocynaceae)
- It's a highly polar cardioactive glycoside
- Acts as a cardiotonic and is administered intravenously for prompt therapeutic effect
- It's absorbed so slowly and irregularly from the alimentary canal that oral administration is not recommended and is considered unsafe
Oleander
- The leaves of Nerium oleander (Apocynaceae) have been used to treat cardiac insufficiency
- The main constituent is oleanderin, which is a promising agent for anticancer treatment
- Oleander has historically been considered a poisonous plant because some of its compounds may exhibit toxicity, especially to animals, when consumed in large amounts
Squill bulb
- The white variety of Urginea maritima is known as white or Mediterranean squill
- Urginea indica is known as Indian squill (Liliaceae)
- Squill glycosides have a six-membered doubly unsaturated lactone ring at position C-17
- They have at least one double bond in the steroid nucleus
- Used as an expectorant and possesses emetic, cardiotonic, and diuretic properties
Red squill
- It consists of the bulb of the red variety of Urginea maritima and is mostly used as rat poison

Mechanism of Action

Cardiac glycosides act by inhibiting the Na+/K+ ATPase enzyme
This enzyme maintains the concentration of K+ inside the cell and Na+ outside the cell
Inhibition of the enzyme blocks K+ transport back into the cell, increasing its concentration in the extracellular fluid
At the same time, Na+ ions enter the cell, facilitating the entry of Ca+2 which is essential for the contraction of actin and myosin
Therefore, cardiac glycosides are used in the treatment of congestive heart failure.

Side Effects

Cardiac glycosides can cause various side effects, including:
- Nausea
- Vomiting
- Diarrhea
- Loss of appetite
- Arrhythmias
- Heart block
- Visual disturbances
It is important to monitor patients carefully for these side effects and adjust the dosage as needed.

Metabolism

Metabolism refers to all chemical transformations occurring in living organisms, essential for their survival.
Metabolites are the end products and intermediates formed during metabolic processes.
Primary metabolites directly contribute to normal growth, development, and reproduction.
Primary metabolites are produced during the growth phase due to energy metabolism, and are crucial for proper growth.
Primary metabolites include alcohols (ethanol, lactic acid), amino acids (L-glutamate, L-lysine), and citric acid.
Secondary metabolites are organic compounds formed through the modification of primary metabolite synthases, typically during the stationary phase of growth.
Secondary metabolites play a role in ecological functions:
- Defense mechanisms (antibiotics, pigmentation)
- Ecological interactions

Biosynthesis of Secondary Metabolites

Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products.
Simple compounds are modified, converted, or joined to form macromolecules, often involving metabolic pathways.
Building blocks for secondary metabolites are derived from primary metabolites, mainly from photosynthesis, glycolysis, and the Krebs cycle.
Key building block molecules include:
- Acetyl CoA
- Shikimic acid
- Mevalonic acid
- Malonic acid

Shikimic Acid Pathway

The shikimic acid pathway is the foundation for the biosynthesis of phenolic compounds, alkaloids, and other secondary metabolites.
This pathway takes place in chloroplast plant cells and utilizes phenylpropanoid precursors.
Aromatic compounds, a type of secondary metabolite, are abundant in plants and their expression is triggered by environmental stresses (pathogens, herbivores, pH, temperature, UV, salinity, heavy metals).
The shikimic acid pathway is also known as the chorismate pathway.
The pathway starts with two substrates: phosphoenol pyruvate and erythrose-4-phosphate, and ends with chorismate, a precursor for the synthesis of three aromatic amino acids.
Aromatic amino acids (phenylalanine, tyrosine, tryptophan) are produced by the shikimate pathway and serve as building blocks for proteins, alkaloids, phenols, and other biosynthesis processes.
The shikimate pathway links central and specialized metabolism in plant cells and carbon degradation during the synthesis of secondary metabolites.

Malonic Acid (Malonate/Acetate) Pathway

The acetate pathway operates with the involvement of acyl carrier protein (ACP) to produce fatty acylthioesters of ACP.
These acyl thioesters are crucial intermediates in fatty acid synthesis.
Acetyl CoA units produce fatty acids with even numbers of carbons, ranging from butyric to arachidic acid.
Malonyl CoA, formed from acetyl CoA by the addition of CO2, is the primary substrate for fatty acid synthase.

Mevalonic Acid (Mevalonate) Pathway

The mevalonic acid (MVA) pathway, or isoprenoid pathway, involves the synthesis of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR).
This pathway plays a critical role in cellular metabolism in eukaryotes, archaea, and some bacteria, including cholesterol biosynthesis and protein production.
Cholesterol is used to build cell membrane structure, steroid hormones, myelin sheaths in the nervous system, vitamin D precursors, and synaptic vesicles.
The MVA pathway produces isopentenyl pyrophosphate (IPP) and its isomer dimethylallyl pyrophosphate (DMAPP).
These two intermediates are the basic building blocks of isoprenoid compounds.
They build various isoprenoid compounds, including:
- Geranyl pyrophosphate (C10-monoterpenes)
- Farnesyl pyrophosphate (C15-sesquiterpenes)
- Geranyl-geranyl pyrophosphate (C20-diterpenes)
Farnesyl pyrophosphate is used to produce squalene, and its subsequent cyclization generates cholesterol and triterpenoids.

Vitamin E

Structurally related tocopherol analogs, including B, gamma, and delta-tocopherols, occur in nature but possess low vitamin E activity.
Dietary sources include plant oils, green vegetables, whole grains, egg yolks, and meats.
Wheat germ oil is a traditional source of vitamin E for therapeutic purposes.
Vitamin E is a major lipid-soluble antioxidant that protects cell membranes, proteins, and DNA from oxidation.
Prevents oxidation of polyunsaturated fatty acids and lipids in cells.
Contributes to cellular health.
Deficiency can lead to nerve and muscle damage, resulting in loss of feeling in arms and legs, loss of body movement control, muscle weakness, and vision problems.
A weakened immune system is another sign of deficiency.

Vitamin K

Refers to 2-methyl-1,4-naphthoquinone and its derivatives.
Widely distributed in dairy products, many fruits and vegetables, especially green leafy vegetables.
The intestinal microflora provides a significant portion of the normal human supply of vitamin K.
Primarily acts in blood clotting (antihemorrhagic activity).
Treatment for bleeding events caused by warfarin (anticoagulant drug) overdose.
Helps in the metabolism of bone proteins (osteocalcin).
Without vitamin K, osteocalcin cannot bind to minerals needed for bone formation, resulting in poor bone mineralization.
Regulates blood calcium levels.
Hemorrhage is the most common symptom in vitamin K deficiency.

Vitamin B-Complex

Vitamin B1 (Thiamine)

Thiamine or vitamin B1 consists of substituted pyrimidine and thiazole rings linked by a methylene bridge.
Commercial supplies are prepared by chemical synthesis and often used as the hydrochloride salt.
Stable in acidic environments but readily decomposes above pH 5.0.
Approximately 50% of the vitamin in foods is destroyed during cooking.
Good dietary sources are whole grains, legumes, and meats.
Alcohol inhibits its absorption.
Participates in energy metabolism by converting carbohydrates, lipids, and proteins into energy.
Plays a key role in nerve and muscle activity.
May be helpful for those with Alzheimer’s disease.
Promotes brain function and the development of myelin sheaths.
Deficiency can cause several clinical syndromes, including Wernicke encephalopathy and beriberi.
Risk factors include alcohol dependence, malabsorption, and a thiamine-deficient diet.

Vitamin B2 (Riboflavin)

Yellow, heat-stable substance slightly soluble in water.
Sensitive to light and can change into lumichrome or lumiflavin, depending on the acidity or alkalinity of the irradiated solution; neither form has physiological activity.
Yeast is the richest natural source.
Main dietary sources include dairy products, eggs, legumes, and meats.
Small amounts are found in cereal grains, fruits, and green vegetables.
Stable during cooking when protected from light.
Occurs in foods in free form and as riboflavin 5'-phosphate (Flavin mononucleotide or FMN) and flavin adenine dinucleotide (FAD).
Nucleotides are hydrolyzed to riboflavin in the upper gastrointestinal tract.
Free riboflavin is readily absorbed into cells of the intestinal mucosa by an active transport system enhanced by bile salts.
Acts as a coenzyme in numerous oxidation-reduction reactions essential for energy release from carbohydrates, fats, and proteins.
Stimulates growth and reproduction.
Plays a role in vision.
Involved in the conversion of vitamins B6, folic acid, and niacin into their active coenzyme forms.
Neutralizes free radicals, acting as an antioxidant.
Deficiency can cause stomatitis and dermatitis.

Vitamin B3 (Niacin)

Simple pyridine derivative that prevents pellagra.
Niacinamide also has anti-pellagra activity and is used for dietary and therapeutic purposes.
Readily absorbed from the gastrointestinal tract under normal circumstances.
Good dietary sources are meats, fish, and dairy products.
Roasting coffee beans releases significant amounts of niacin and develops a characteristic flavor.
Tryptophan is converted to niacin in the body.
Acts as a coenzyme in energy-transfer reactions.
Similar to riboflavin coenzymes in carrying hydrogen during metabolic reactions.
Protects against neurological degeneration and Alzheimer’s disease.
Helps lower LDL cholesterol.
Lowers the risk of cardiovascular diseases and eases arthritis.
Pellagra is the classic niacin-deficiency condition.
Symptoms involve the nervous system, skin, and gastrointestinal tract, often summarized as the 3Ds: dementia, dermatitis, and diarrhea.
Oral lesions, especially angular stomatitis and red tongue, are more distinct than other symptoms.

Vitamin B5 (Pantothenic Acid)

Component of the vitamin B complex, sometimes known as the “chick antidermatitis factor".
Naturally occurring compound that yields β-alanine and pantoic acid upon hydrolysis.
Animal organs (heart, kidney, and liver) and cereal grains are rich dietary sources.
Turns food into energy.
Involved in the synthesis of lipids, neurotransmitters, steroid hormones, and hemoglobin.
Maintains and repairs skin and hair tissues and cells.
Helps heal wounds and lesions.
Normalizes blood lipid profile.
Deficiency can cause fatigue and sleep disturbances.

Vitamin B6

Term applied to pyridoxol, pyridoxal, and pyridoxamine, three closely related, naturally occurring pyridine derivatives with comparable physiological activity.
Pyridoxine (pyridoxol) is the predominant form in plants, and the term used in pharmacy and medicine.
Pyridoxal and pyridoxamine occur in animal tissues.
Pyridoxine is the most stable, so synthetically prepared pyridoxine is usually used in exogenous dietary supplementation and therapeutic purposes.
Good dietary sources include beef liver, tuna, salmon, fortified cereals, chickpeas, and poultry.
Some vegetables and fruits, especially dark leafy greens, pineapple, papaya, oranges, and cantaloupe, also contain vitamin B6.
Required for biological reactions like amino acid metabolism, neurotransmitter synthesis, and red blood cell formation.
Acts as a crucial co-factor for diverse biochemical reactions that regulate basic cellular metabolism.
Deficiency can cause peripheral neuropathy.
Symptoms resemble those of niacin and riboflavin deficiencies and include neurological abnormalities, skin lesions, and hypochromic microcytic anemia.

Vitamin B7 (Biotin)

Found in eggs, fish, meat, seeds, nuts, and certain vegetables (sweet potatoes).
Plays an important role in metabolism as a coenzyme that transfers carbon dioxide.
Crucial for breaking down food (carbohydrates, fats, and proteins) into energy.
Involved in many cellular reactions, particularly in fat and protein metabolism of hair roots, fingernails, and skin.
Used in fatty acid synthesis.
Deficiency can cause fatigue, depression, and dermatitis.

Vitamin B9 (Folate)

Terms include folic acid, folacin, pteroylglutamic acid, and vitamin B9.
Sources include beans, peanuts, sunflower seeds, fresh fruits, fruit juices, whole grains, and liver.
Essential for brain development and function.
Aids in the production of DNA and RNA.
Involved in the metabolism of vitamins and amino acids.
Crucial during early pregnancy to reduce the risk of birth defects of the brain and spine.
Required for the synthesis of glycine, methionine, and nucleotides T and U.
Deficiency states include megaloblastic and macrocytic anemias and glossitis.

Vitamin B12 (cobalamins)

Refer to a series of porphyrin-related corrinoid derivatives that function as extrinsic factors to prevent pernicious anemia.
Cyanocobalamin is the most stable form and is frequently used in therapy.
Hydroxocobalamin also finds some therapeutic use, with the cyano group replaced by a hydroxyl substituent.
Acts as a coenzyme in the conversion of homocysteine to methionine.
Plays a role in the metabolism of fatty acids and amino acids.
Involved in the production of neurotransmitters.
Maintains the lining surrounding and protecting nerve fibers.
Bone cell activity depends on vitamin B12.
Plays a significant role in DNA synthesis.
Helps in brain function and the synthesis of red blood cells.
Deficiency usually involves rapidly dividing cells of the hematopoietic system (megaloblastic anemia) and irreversible neurological damage (defective myelin nerve sheaths).
Symptoms include irritability, weakness, memory loss, mood swings, and a tingling or numbness sensation in the arms and legs.

Vitamin C (L-Ascorbic Acid)

Naturally occurring vitamin that prevents scurvy and has antioxidant properties.
Exists in equilibrium with dehydro-L-ascorbic acid, an oxidized form, which also has antiscorbutic properties.
Least stable of all vitamins.
Good dietary sources include citrus fruits, tomatoes, strawberries, and other fresh fruits and vegetables.
Content is preserved on freezing, but up to 50% is lost upon cooking.
One of its important properties is antioxidant activity.
Functions in enzyme activation and oxidative stress reduction.
Plays a role in collagen synthesis and iron absorption.
Provides defense against infections and inflammation.
Helps prevent certain diseases like cancer, the common cold, cardiovascular diseases, and cataracts.
Deficiency causes scurvy.

Glycosides

Organic compounds, usually of plant origin, composed of a sugar portion linked to a non-sugar moiety by a glycosidic bond.
Sugar portion is called glycon.
Non-sugar portion is called aglycon or genin.
Four basic classes: C-glycosides, O-glycosides, S-glycosides, and N-glycosides.
Yield one or more sugars upon enzymatic or acid hydrolysis.
Sugar component can be mono-, di-, tri-, or tetrasaccharides.

Alpha and Beta Glycosides

Sugars exist in isomeric α and β forms, so both are theoretically possible.
β-form is the one that predominantly occurs in plants.
Diastereoisomers differ in configuration about the anomeric carbon (C-1).
α anomer has a hydroxyl group on the anomeric carbon down in relation to the cyclic structure.
β anomer has a hydroxyl group on the anomeric carbon up in relation to the cyclic structure.
Chemically, glycosides are acetals with the hydroxyl group (OH) of the glycon condensed with the hydroxyl group of the aglycone.
Sugars exist as cyclic hemiacetals (R-O-C-OH group), while glycosides are mixed acetals (R-O-C-O-R group).
Glycosides are cleaved in the body to glycon and aglycone parts.
Glycon confers solubility properties, important for absorption and distribution.
Aglycone is responsible for the pharmacological activity.

Physical and Chemical Properties of Glycosides

No generalizations are possible regarding stability due to structural complexity.
There are differences in their solubility properties.

Solubility

Most are soluble in water or hydroalcoholic solutions and insoluble or less soluble in non-polar organic solvents because the sugar residues increase water solubility.
Aglycone part is soluble in non-polar organic solvents like benzene, ether, and chloroform.

Stability and Hydrolytic Cleavage

Acids and alkali: Glycosides are hydrolyzed by heating with dilute acid, cleaving the glycosidic linkages. They are relatively stable towards alkalis.
Enzyme hydrolysis: Specific enzymes, usually found in the same plant, in separate compartments, can hydrolyze glycosides. One enzyme can hydrolyze different glycosides, but α and β stereo-isomers of the same glycoside usually are not hydrolyzed by the same enzyme. Emulsin hydrolyzes most β-glycoside linkages, while maltase and invertase are α-glycosidases.

Shape, Color, Taste, and Odor:

Shape: Glycosides are solid, amorphous, and nonvolatile.
Color: Colorless except for flavonoids (yellow) and anthraquinones (red or orange).
Taste: Most are bitter.
Odor: Odorless except for saponin (glycyrrhizin).

Importance of Glycosides

Play an important role in plant life.
Serve as sugar reserves, waste products of plant metabolism, a means of detoxification, regulators of osmosis, regulators of the supply of important substances in metabolism, and a defense against microbial invasion. Aglycones are sometimes suggested to be antiseptics and bactericidal.
Many therapeutic agents are derived from glycosides, contributing to almost every therapeutic class. Examples include:
- Cardioactive glycosides: Digitalis, strophanthus, squill.
- Laxative drugs: Senna, aloe, rhubarb, cascara sagrada, frangula.
- Sinigrin: From black mustard, yields allyl isothiocyanate (irritant).

Biosynthesis of Glycosides

Pathways are variable depending on the aglycone and glycone units.
Aglycone and sugar parts are biosynthesized separately and then coupled to form a glycoside.
Coupling occurs by phosphorylation of a sugar to yield a sugar 1-phosphate, which reacts with uridine triphosphate to form a uridine diphosphate sugar (UDP-sugar) and inorganic phosphate.
UDP-sugar reacts with the aglycone to form the glycoside and a free UDP.

Extraction of Glycosides

Inactivate hydrolyzing enzymes by putting the plant in boiling water or alcohol.
Defatting or purification of the plant material (seeds).
Treatment with lead acetate: Precipitates tannins and other non-glycosidal impurities.
Removal of excess lead acetate: By passing hydrogen sulfide (H2S) gas through the solution.
Filter and concentrate the extract: To obtain the crude glycoside.
Purify the crude glycosides: By chromatography or crystallization.

Cardioactive Glycosides

Characterized by their specific action on cardiac muscle, increasing tone, excitability, and contractility.
Aglycones are referred to as "cardiac genin" and are steroidal in nature.
Derivatives of cyclopentaphenanthrene, with an unsaturated lactone ring attached to C17.

Structure of Glycosides

Cardenolide: Contains a five-membered lactone ring. Examples include digitoxigenin and glycosides of digitalis and strophanthus species.
Scilladienolide (Bufadienolide): Contains a six-membered lactone ring. Examples include scillarenin, squill glycosides, and bufotoxin.

Cardenolide Structure (C23)

Possesses a butenolide (4 carbons) attached at C17, also known as an α,β-unsaturated lactone ring.

Scilladienolide Structure (C24)

Possesses a pentadienolide (5 carbons with two double bonds) attached at C17, also known as a pentenolide.

Color Tests

The two types of lactone rings (cardenolide and scilladienolide) give different reactions to certain color tests.

Bufadienolides

Bufadienolides are a type of cardiac glycoside
The glycone portion of cardiac glycosides can contain up to four sugar molecules
Bufadienolides contain a C3 unit (in addition to the C21 steroid)
Bufadienolides are condensation products of a C21 steroid and a C3 unit.
In the nomenclature of cardioactive glycosides, the configuration of functional groups is denoted first
The type of glycoside (e.g., cardenolide, dienolide, cardanolide, bufanolide) is denoted based on the number of double bonds in the molecule

Cardiac Glycosides

Cardiac glycosides contain a β-OH group at position C-3 that is glycosidically linked to a mono, di, tri, or tetrasaccharide.
Cardiac glycosides also contain a β-OH group at position C-14.
Cardiac glycosides contain an unsaturated 5 or 6-membered lactone ring at position C-17 in the β configuration.

Digitalis

Digitalis is derived from the dried leaves of Digitalis purpurea
Digitalis contains various glycosides, including digitoxin, gitoxin, and gitaloxin
Digitalis acts through inhibiting the sodium-potassium ATPase enzyme
It is used in the treatment of congestive heart failure
Digitalis lanata also contains various glycosides including digitoxin, gitoxin, and gitaloxin.

Strophanthus

Strophanthus is derived from the dried seeds of Strophanthus kombe or Strophanthus hispidus
Strophanthus is a cardiotonic
Strophanthus contains various glycosides including k-strophanthoside, k-strophanthin-B and cymarin.

Oleander

Oleander is derived from the leaves of Nerium oleander
Oleander is used to treat cardiac insufficiency
Oleanderin is a constituent of oleander and is studied for anticancer treatment

Squill

Squill is derived from the bulbs of Urginea maritima or Urginea indica
Squill glycosides differ from cardiac glycosides in having a six-membered, doubly unsaturated lactone ring in position C-17.
Squill glycosides also have at least one double bond in the steroid nucleus
Squill has expectorant, emetic, cardiotonic and diuretic properties.

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Test your knowledge on primary and secondary metabolites in this engaging quiz. Explore their roles in organisms, industrial applications, and key biochemical processes such as photosynthesis and the Calvin cycle. A great way to solidify your understanding of metabolic pathways!

Biochemistry Quiz on Metabolites

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Questions and Answers

Which of the following is NOT classified as a primary metabolite?

Primary metabolites play a crucial role in an organism's growth and reproduction.

What is the role of secondary metabolites in organisms?

___ is a secondary metabolite derived from various plants with important clinical uses.

Which organism is known for producing citric acid?

Secondary metabolites are formed primarily during the growth phase of an organism.

Name one example of a secondary metabolite used in industry.

Match the following primary metabolites with their uses:

What type of receptors does atropine act on?

Erythromycin is produced from organisms classified under Bacillus subtilis.

What is the primary process by which plants convert light energy into chemical energy?

The light-dependent reactions of photosynthesis occur in the ______ of the chloroplast.

Match the following steps of the Calvin cycle with their descriptions:

Which of the following substances is produced during the light reactions of photosynthesis?

Bacitracin is commonly used as an oral antibiotic.

What is the final product of glycolysis?

The chemical equation for the light reaction of photosynthesis can be simplified to: 2H2O + 2NADP+ + 3ADP + 3Pi → O2 + ______ + 3ATP

Match the following biochemical pathways with their description:

Which of the following is a reactant in the dark reactions of photosynthesis?

Which of the following vitamins is classified as water soluble?

Chlorophyll a is the main pigment in most green plants.

Vitamins can be synthesized by the body.

What is the initial acceptor molecule in the Calvin cycle?

The Krebs cycle takes place in the ______ of the mitochondria.

What is the primary natural form of Vitamin A?

Excessive intake of _______ soluble vitamins may be toxic.

Which vitamin is referred to as the 'sunshine vitamin'?

Beta-carotene can be converted into Vitamin A by the body.

What is the role of Vitamin D in the body?

Vitamin _______ is essential for vision, growth, and immune function.

Which of the following dietary sources is rich in Vitamin E?

Match the following vitamins with their primary deficiency states:

How are fat-soluble vitamins absorbed in the body?

Vitamin E is a specific term for one particular form of tocopherol.

What condition can arise from Vitamin D deficiency in adults?

The vitamins can be classified as either _______ soluble or water soluble.

Which vitamin is primarily derived from plant sources such as mushrooms?

What is the primary location where the Krebs cycle occurs?

The shikimic acid pathway is utilized by plants only for synthesizing fatty acids.

What are the two substrates that start the shikimic acid pathway?

The main product of the mevalonate pathway is __________.

Match the following metabolic pathways with their main products:

Which of these compounds is considered a building block in biosynthesis?

The acetate pathway is primarily for synthesizing amino acids.

What are the main intermediates produced by the mevalonate pathway?

C2 building blocks in biosynthesis are derived from __________.

Match the following pathways with their type of secondary metabolites:

What initiates the shikimic acid pathway reactions?

Environmental stresses do not influence the expression of secondary metabolites.

Name an enzyme involved in the shikimic acid pathway.

Malonyl-CoA is formed from __________ by the addition of CO2.

Which acid is a key precursor in the biosynthesis of aromatic amino acids?

Which of the following is a common dietary source of Vitamin E?

Vitamin K is primarily involved in blood clotting and can help in the metabolism of bone proteins.

Name one symptom of Vitamin E deficiency.

Vitamin B1 is also known as _____ .

Match the following vitamins with their primary functions:

What is a major health consequence of Vitamin K deficiency?

Riboflavin is sensitive to light and can change to lumichrome or lumiflavin.

What is the common deficiency condition associated with Vitamin B3?

Vitamin B2 is also known as _____ .

Which vitamin is described as a lipid-soluble antioxidant?

Thiamine is stable in an acidic environment but decomposes above pH 5.0.

Identify one dietary source of Vitamin B1.

Niacin is also called _____ .

Match the following vitamins with sources:

Which plant is known for containing cardiac glycosides and has historically been considered poisonous?

Ouabagenin has an aldehydic group at C-10.

What is the main therapeutic effect of Strophanthin when administered intravenously?

The sugar component of Ouabagenin is ______.

What vitamin is known for its role in energy metabolism and synthesis of lipids?

Match the following substances with their properties or uses:

Vitamin B6 is primarily found in animal tissues and is used for amino acid metabolism.

What condition can arise from a deficiency of Vitamin B12?

Vitamin C is essential for the synthesis of __________.

Match the vitamin to its key use: