Podcast Beta
Questions and Answers
Which of the following amino acids are produced by the shikimate pathway?
The malonate pathway is primarily responsible for the synthesis of amino acids.
False
What is the role of HMGCR in the mevalonate pathway?
It is involved in cholesterol biosynthesis.
The shikimate pathway connects central and specialized metabolism in the plant cell and carbon degradation during the synthesis of secondary ______ compounds.
Signup and view all the answers
Match the following pathways with their primary products:
Signup and view all the answers
What is produced from acetyl-CoA in the malonate pathway?
Signup and view all the answers
Isopentenyl pyrophosphate (IPP) is an intermediate in the malonate pathway.
Signup and view all the answers
What is the main function of cholesterol produced in the mevalonate pathway?
Signup and view all the answers
What vitamin is associated with the prevention of pellagra?
Signup and view all the answers
Niacinamide has no therapeutic purposes.
Signup and view all the answers
What deficiency causes symptoms of stomas and dermatis?
Signup and view all the answers
Vitamin B3 is also known as __________.
Signup and view all the answers
Match the following terms with their descriptions:
Signup and view all the answers
What is the role of vitamin B3 in terms of free radicals?
Signup and view all the answers
A deficiency of vitamin B3 leads to __________.
Signup and view all the answers
What are the two forms of Vitamin B3 mentioned?
Signup and view all the answers
What is one of the main dietary sources of riboflavin?
Signup and view all the answers
Riboflavin is sensitive to light and can change into lumichrome or lumiavine, both of which have physiological activity.
Signup and view all the answers
What condition can be caused by a diet low in thiamine?
Signup and view all the answers
Yeast is the richest natural source of ______.
Signup and view all the answers
Which of the following is NOT a function of vitamin B2 (riboflavin)?
Signup and view all the answers
Riboflavin is stable during cooking in the presence of light.
Signup and view all the answers
What is the active form of riboflavin that is used as a coenzyme?
Signup and view all the answers
Match the following functions of vitamin B2 (riboflavin) with their descriptions:
Signup and view all the answers
Which of the following is NOT a dietary source of niacin?
Signup and view all the answers
Tryptophan can be converted into niacin in the body.
Signup and view all the answers
What is the classic niacin-deficiency condition called?
Signup and view all the answers
Niacin helps to lower _____ cholesterol.
Signup and view all the answers
Match the following symptoms with the corresponding 'D' in niacin deficiency:
Signup and view all the answers
What important function does niacin perform in metabolic reactions?
Signup and view all the answers
Symptoms of niacin deficiency can be summarized as the 3D's.
Signup and view all the answers
Name one disease against which niacin provides protection.
Signup and view all the answers
What is the solubility characteristic of the aglycon part of glycosides?
Signup and view all the answers
Glycosides are stable to both acids and alkalis.
Signup and view all the answers
Name one therapeutic class that glycosides contribute to.
Signup and view all the answers
Most glycosides have a _____ taste.
Signup and view all the answers
Match the following glycosides with their primary therapeutic use:
Signup and view all the answers
What role do glycosides play in plant metabolism?
Signup and view all the answers
All glycosides are colorless.
Signup and view all the answers
What specific function does emulsin have with glycosides?
Signup and view all the answers
What is the primary natural form of Vitamin A?
Signup and view all the answers
Vitamin D2 is primarily found in animal-sourced foods.
Signup and view all the answers
Name one effect of Vitamin A deficiency.
Signup and view all the answers
Vitamin A plays a critical role in __________ function.
Signup and view all the answers
Match the vitamin with its respective primary food source:
Signup and view all the answers
Which condition can result from Vitamin A deficiency?
Signup and view all the answers
What is the primary function of Vitamin D?
Signup and view all the answers
Vitamin A can only be obtained from animal sources.
Signup and view all the answers
What is the primary function of Vitamin K in the human body?
Signup and view all the answers
Vitamin K deficiency can lead to hemorrhage.
Signup and view all the answers
Name one dietary source of Thiamine (Vitamin B1).
Signup and view all the answers
Vitamin K primarily helps in the metabolism of bone proteins like __________.
Signup and view all the answers
Match the B vitamin with its primary function:
Signup and view all the answers
What role does Vitamin B1 (Thiamine) play in the body?
Signup and view all the answers
What is the consequence of Vitamin B1 deficiency?
Signup and view all the answers
Cooking can destroy about 50% of Vitamin B1 in foods.
Signup and view all the answers
Which of the following diseases can Vitamin C help prevent?
Signup and view all the answers
The β form of glycosides is the primary form that occurs in plants.
Signup and view all the answers
What happens to glycosides inside the body?
Signup and view all the answers
Which of the following statements about glycosides is true?
Signup and view all the answers
Glycosides can be classified into four basic classes, which include C-glycosides, O-glycosides, S-glycosides, and __________.
Signup and view all the answers
Glycosides can be hydrolyzed by heating with a dilute acid.
Signup and view all the answers
Match the following glycosides with their properties:
Signup and view all the answers
Name one role that glycosides serve in plants.
Signup and view all the answers
Which part of glycosides is responsible for pharmacological activity?
Signup and view all the answers
Most glycosides are insoluble in water.
Signup and view all the answers
Saponin is a type of glycoside known for its ______ odor.
Signup and view all the answers
What type of glycosides yield one or more sugars upon enzymatic or acid hydrolysis?
Signup and view all the answers
Match the following types of glycosides with their effects:
Signup and view all the answers
What property makes glycosides largely stable against certain conditions?
Signup and view all the answers
Most glycosides are considered sweet in taste.
Signup and view all the answers
What is the function of the enzyme emulsin in relation to glycosides?
Signup and view all the answers
Which of the following types of glycosides is characterized by having two double bonds?
Signup and view all the answers
Cardanolide is a type of glycoside that contains at least one double bond.
Signup and view all the answers
What is the primary source of cardioactive glycosides derived from?
Signup and view all the answers
Digitalis purpurea contains the glycosides __________, __________, and __________.
Signup and view all the answers
Match the following Digitalis species with their glycosides:
Signup and view all the answers
What is the average concentration of glycosides in Digitalis purpurea?
Signup and view all the answers
Bufadienolides are derived from a condensation of a C21 steroid and a C2 unit.
Signup and view all the answers
Which aglycone is not found in Digitalis purpurea but is found in Digitalis lanata?
Signup and view all the answers
Study Notes
Aromatic Amino Acid Synthesis
- Tryptophan (L-Trp), Tyrosine (L-Tyr), and Phenylalanine (L-Phe) are produced by the shikimate pathway.
- These aromatic amino acids serve as building blocks for proteins, alkaloids, phenols, and other biosynthetic processes.
Shikimate Pathway
- Connects central and specialized metabolism in plant cells.
- Involved in carbon degradation during secondary metabolite synthesis.
Malonic-Acid (Malonate/Acetate) Pathway
- Operates with acyl carrier protein (ACP) to produce fatty acylthioesters.
- Fatty acylthioesters are key intermediates in fatty acid synthesis.
- Produces fatty acids with an even number of carbons, ranging from butyric to arachidic acid.
Acetyl-CoA
- Direct precursor only for the methyl end of the growing fatty acid chain.
- Acetyl group of acetyl-CoA is modified to provide the actual substrate for fatty acid synthase.
Malonyl-CoA
- A 3-carbon dicarboxylic acid, malonate, bound to Coenzyme A.
- Formed from acetyl-CoA by adding CO2 with the help of biotin cofactor in the enzyme acetyl-CoA carboxylase.
Mevalonic-Acid (Mevalonate) Pathway
- Also known as the isoprenoid pathway.
- Involves the synthesis of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR).
- Core metabolic pathway for various cellular processes in eukaryotic, archaea, and some bacteria.
Cholesterol Production
- The mevalonate pathway is essential for cholesterol biosynthesis.
- Cholesterol is crucial for building cell membranes, steroid hormone production, myelin sheaths in the nervous system, vitamin D synthesis, and synaptic vesicle formation.
Isopentenyl Pyrophosphate (IPP) and Dimethylallyl Pyrophosphate (DMAPP)
- IPP and DMAPP are produced from mevalonic acid.
- These are the "active isoprene" units, serving as basic building blocks of isoprenoid compounds.
Geranyl Pyrophosphate and Farnesyl Pyrophosphate
- Geranyl pyrophosphate (C10-monoterpenes) is formed from IPP and DMAPP.
- Further association of geranyl pyrophosphate with IPP produces farnesyl pyrophosphate (C15-sesquiterpenes).
Vitamin B2 (Riboflavin)
- Yellow, heat-stable substance slightly soluble in water.
- Sensitive to light, converting into lumichrome or lumiflavin depending on the acidity or alkalinity.
- Lumichrome and lumiflavin have no physiological activity.
Vitamin B2 Sources
- Yeast is the richest natural source.
- Dairy products, eggs, legumes, and meats are primary dietary sources.
- Cereals, fruits, and green vegetables provide small amounts.
- Stable during cooking in the absence of light.
Vitamin B2 Forms
- Vitamin B2 exists in foods in the free form, as riboflavin 5'-phosphate (Flavin mononucleotide or FMN), and flavin adenine dinucleotide (FAD).
- Nucleotides are hydrolyzed to riboflavin in the upper gastrointestinal tract.
Vitamin B2 Absorption
- Freely absorbed into intestinal mucosal cells through an active transport system enhanced by bile salts.
Vitamin B2 Uses
- Coenzyme in numerous oxidation-reduction reactions for energy release from carbohydrates, fats, and proteins.
- Stimulates growth and reproduction.
- Plays a role in vision.
- Necessary for the conversion of vitamins B6, folic acid, and niacin into their active coenzyme forms.
- Acts as an antioxidant.
Vitamin B2 Deficiency
- Can cause stomatitis and dermatitis.
Vitamin B3 (Niacin)
- Simple, naturally occurring pyridine derivative that prevents pellagra.
Niacinamide
- Occurs naturally and has anti-pellagra activity.
- Used for dietary and therapeutic purposes.
- Readily absorbed from the gastrointestinal tract under normal circumstances.
Vitamin B3 Sources
- Meats, fish, and dairy products are good dietary sources.
- Roasting coffee beans releases significant niacin and develops a characteristic flavor.
- The body can convert tryptophan into niacin.
Vitamin B3 Uses
- 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.
- Reduces the risk of cardiovascular diseases and eases arthritis.
Vitamin B3 Deficiency
- Pellagra is the classic niacin-deficiency condition.
- Symptoms affect the nervous system, skin, and gastrointestinal tract.
- Often characterized by the "3Ds": dementia, dermatitis, and diarrhea.
- Oral lesions, such as angular stomatitis and red tongue, are more distinct than other symptoms.
Glycosides
- Sugar-based compounds with a sugar moiety (glycone) linked to a non-sugar moiety (aglycone).
- The sugar moiety increases water solubility.
- The aglycone part is soluble in non-polar (organic) solvents such as benzene, ether, and chloroform.
Glycosides: Stability and Hydrolytic Cleavage
- Acids and alkali: Glycosides can be hydrolyzed by heating with a dilute acid, breaking the glycosidic linkages. Glycosides are relatively stable towards alkalis.
- Enzyme hydrolysis: Specific enzymes, usually found in the same plant in separate compartments, are capable of hydrolyzing glycosides. Each glycoside has a specific enzyme for hydrolysis.
- The same enzyme can hydrolyze different glycosides, but α and β stereoisomers of the same glycoside are usually not hydrolyzed by the same enzyme.
- Emulsin hydrolyzes most β-glycoside linkages, while maltase and invertase are α-glycosidases, capable of hydrolyzing α-glycosides.
Glycosides: Shape, Color, Taste, and Odor
- Shape: Glycosides are solid, amorphous, and non-volatile.
- Color: Glycosides are colorless, except flavonoids (yellow) and anthraquinones (red or orange).
- Taste: Most glycosides are bitter.
- Odor: Glycosides are odorless, except saponin (glycyrrhizin).
Glycosides: Importance
- Play crucial roles in plant life, involved in various functions:
- Sugar reserves.
- Waste products of plant metabolism.
- Detoxification mechanism.
- Osmotic regulation.
- Regulation of substance supply for metabolism.
- Defense against microbial invasion (aglycones are thought to be antiseptics and bactericidal).
Glycosides: Therapeutic Importance
- Many therapeutic agents are derived from glycosides, contributing to almost every therapeutic class:
- Cardiac glycosides from digitalis, strophanthus, squill, and others.
- Laxative drugs like senna, aloe, rhubarb, cascara sagrada, and frangula, containing emodin and other anthraquinone glycosides.
- Sinigrin, a glycoside from black mustard, yields allyl isothiocyanate, a potent local irritant.
Vitamin A (Retinol)
- Vitamin A is a term used for all derivatives of β -ionone, except carotenoids.
- Retinol is the primary natural form of vitamin A.
- Other known forms include acetate and palmitate esters of retinol.
- The body readily absorbs (80-90%) retinol from the normal intestinal tract.
- The liver and other body tissues store retinol.
- Under normal circumstances, approximately one third of ingested vitamin A is stored.
- Fish liver oils are natural sources of vitamin A.
- Animal organs like heart, kidney, and liver are common dietary sources.
- Some plant carotenoids in carrots and green leafy vegetables also contribute to vitamin A activity.
- Only carotenoids with at least one unhydroxylated β -ionone ring (α-, β -, and -y-carotene and cryptoxanthin) can convert to vitamin A.
- In intestinal mucosal cells, β-carotene oxygenase cleaves β-carotene and related carotenoids to yield retinal, primarily reduced to retinol by NADH.
Vitamin A Uses
- Vision
- Growth and development
- Immune function
- Red blood cell formation
- Skin and bone formation
- Regulating gene transcription
Vitamin A Deficiency
- Can result in a variety of conditions, including nyctalopia (night blindness), xerophthalmia, hyperkeratosis of the skin, growth retardation, and decreased resistance to infection.
Vitamin D
- Vitamin D refers to several related steroids and their metabolites, essential for calcium absorption and utilization.
- Two forms of vitamin D exist: Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol).
- Vitamin D3 is found only in animal-sourced foods.
- Vitamin D2 is mainly found in plant sources and fortified foods.
- A weakened immune system is another sign of deficiency.
Vitamin K (Naphthoquinone)
- Vitamin K is a term for 2-methyl-1,4-naphthoquinone and its derivatives.
- There are five main types of vitamin K: K1 (phylloquinone), K2 (menaquinone), K3 (Menadione), and K4 (Menadiol).
- Vitamin K is widely distributed in dairy products, fruits, and vegetables, with green leafy vegetables being particularly rich sources.
- The intestinal microflora also provides a significant portion of the human supply of vitamin K.
Vitamin K Uses
- Primarily functions in blood clotting (antihemorrhagic activity).
- Used to treat bleeding events caused by warfarin overdose.
- Helps in the metabolism of bone proteins, such as osteocalcin.
- Without vitamin K, osteocalcin cannot bind to minerals, leading to poor bone mineralization.
- Regulates blood calcium levels.
Vitamin K Deficiency
- Hemorrhage is the most common symptom of vitamin K deficiency.
Water-Soluble Vitamins
B Complex Vitamins
Vitamin B1 (Thiamine)
- Thiamine has substituted pyrimidine and thiazole rings linked by a methylene bridge.
- Thiamine is commercially produced through chemical synthesis and is typically used as the hydrochloride salt.
- It is stable in acidic environments but readily decomposes above pH 5.0.
- Cooking can destroy about 50% of the thiamine in foods.
Vitamin B1 Sources
- Whole grains, legumes, and meats are good dietary sources of Thiamine.
- Alcohol inhibits the absorption of Thiamine.
Vitamin B1 Uses
- It is a sulfur-containing vitamin involved in energy metabolism.
- Converts carbohydrates, lipids, and proteins into energy.
- Plays a key role in nerve and muscle activity.
- May be beneficial for people with Alzheimer's disease.
- Contributes to the development of myelin sheaths and improves brain function.
Vitamin B1 Deficiency
- Can cause various clinical syndromes, including Wernicke’s encephalopathy and beriberi.
- It can help prevent diseases such as cancer, the common cold, cardiovascular diseases, and cataracts.
Vitamin C Deficiency
- Can lead to scurvy.
Glycosides
- A plant-derived organic compound composed of a sugar portion (glycon) linked to a non-sugar moiety (aglycon or genin) by a glycosidic bond.
- There are four main classes of glycosides: C-glycosides, O-glycosides, S-glycosides, and N-glycosides.
- Glycosides can be hydrolyzed to yield one or more sugars.
- The sugar component can be mono, di, tri, or tetrasaccharides.
- Glycosides exist in α and β forms, with the β-form prevalent in plants.
- Chemically, glycosides are acetals formed by condensing the glycon's hydroxyl group with the aglycon's hydroxyl group.
- Within the body, glycosides are cleaved into glycon and aglycon parts.
- The glycon contributes to solubility and is important for absorption and distribution in the body.
- The aglycon is responsible for the pharmacological activity.
Physical and Chemical Properties of Glycosides
- No generalizations can be made regarding their stability due to structural complexity.
- Variability exists in their solubility properties:
- Most glycosides are soluble in water or hydroalcoholic solutions but insoluble or less soluble in non-polar organic solvents due to the sugar moiety's water solubility.
- The aglycon part is soluble in non-polar organic solvents like benzene, ether, and chloroform.
-
Stability and Hydrolytic Cleavage:
- Acids and Alkali: Glycosides can be hydrolyzed by heating with dilute acid, breaking the glycosidic linkages, but are stable towards alkalis.
- Enzyme Hydrolysis: Glycosides can be hydrolyzed by specific enzymes, commonly found in the same plant but in separate compartments. Each glycoside has a specific enzyme for hydrolytic action. Some enzymes can hydrolyze various glycosides, but α and β isomers are typically not hydrolyzed by the same enzyme. Emulsin hydrolyzes most β-glycoside linkages, while maltase and invertase are α-glycosidases.
Shape, Color, Taste, and Odor of Glycosides
- Shape: Glycosides are solid, amorphous, and non-volatile.
- Color: Glycosides are typically colorless, except for flavonoids (yellow) and anthraquinones (red or orange).
- Taste: Most glycosides are bitter.
- Odor: Glycosides are usually odorless, except for saponins (glycyrrhizin).
Importance of Glycosides
- Play a crucial role in plant life and are involved in various functions:
- Sugar reserves
- Waste products of plant metabolism
- Detoxification
- Osmosis regulation
- Supply regulation of metabolic substances
- Defense against microorganism invasion (aglycones act as antiseptics and are bactericidal).
Therapeutic Uses of Glycosides
- Many valuable therapeutic agents are derived from glycosides, encompassing various therapeutic classes:
- Cardiac glycosides from digitalis, strophanthus, squill, etc.
- Laxative drugs like senna, aloe, rhubarb, cascara sagrada, and frangula, contain emodin and anthraquinone glycosides.
- Sinigrin from black mustard yields allyl isothiocyanate, a potent local irritant.
Nomenclature of Cardioactive Glycosides
- The sequence of nomenclature is as follows:
- Arrange functional groups according to their configuration.
- Denote α or β configuration.
- Specify the glycoside type.
- Indicate the position of double bonds.
Cardioactive Glycoside Biosynthesis
- Most of the knowledge surrounding steroid biosynthesis comes from studies of cholesterol production.
- The aglycones of cardiac glycosides are derived from mevalonic acid, but the final molecules result from a condensation of a C21 steroid with a C2 unit (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:
- The dried leaf of Digitalis purpurea (Scrophulariaceae).
- Digitalis is Latin for "finger" referring to the finger-shaped corolla, and purpurea is Latin for "purple," indicating the flower's color.
- Constituents: The drug contains numerous glycosides, with the most important being digitoxin, gitoxin, and gitaloxin, totaling about 0.16%. Over 30 other glycosides, including purpurea glycosides A, B, gluco-gitaloxin, and gluco-digitoxigenin, are also present.
- Primary Glycosides: Contain acetylated sugar moieties.
-
Digitalis lanata:
- Contains nearly 70 different glycosides.
- Most are derivatives of five different aglycones, three of which (digitoxigenin, gitoxigenin, and gitaloxigenin) are also found in Digitalis purpurea.
- The other two types are derived from digoxigenin and diginatigenin, found only in Digitalis lanata.
- The leaves are a source of the glycosides digoxin and lanatoside C.
- Lanatoside A, B, and E: 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
-
Where:* DX=Digitoxose, DX(AC)=Acetyldigitoxose, G=Glucose.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz explores the synthesis of aromatic amino acids, including Tryptophan, Tyrosine, and Phenylalanine, through the shikimate pathway. It also examines the malonic-acid pathway and the role of Acetyl-CoA and Malonyl-CoA in fatty acid synthesis.