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Questions and Answers
What is primarily responsible for the tertiary structure of a protein?
What is primarily responsible for the tertiary structure of a protein?
Which type of bond is stronger in contributing to the tertiary structure of proteins?
Which type of bond is stronger in contributing to the tertiary structure of proteins?
What is the quaternary structure of a protein?
What is the quaternary structure of a protein?
Which of the following is NOT a type of protein based on its function?
Which of the following is NOT a type of protein based on its function?
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Which protein acts as a transport protein for oxygen in the blood?
Which protein acts as a transport protein for oxygen in the blood?
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Which of the following is an example of a storage protein?
Which of the following is an example of a storage protein?
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Which class of proteins helps in combating foreign substances in the body?
Which class of proteins helps in combating foreign substances in the body?
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Which of the following statements about hydrophobic interactions is true?
Which of the following statements about hydrophobic interactions is true?
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Which classification of amino acids has more amino groups than carboxylic groups?
Which classification of amino acids has more amino groups than carboxylic groups?
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Which category of amino acids must be obtained through the diet?
Which category of amino acids must be obtained through the diet?
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Which of the following is a pure ketogenic amino acid?
Which of the following is a pure ketogenic amino acid?
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Which classification of amino acids includes those that can convert into both glucose and ketone bodies?
Which classification of amino acids includes those that can convert into both glucose and ketone bodies?
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Which of the following amino acids is classified as an imino acid?
Which of the following amino acids is classified as an imino acid?
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Which protein classification produces only amino acids upon hydrolysis?
Which protein classification produces only amino acids upon hydrolysis?
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Which amino acid is an essential amino acid involved in various metabolic functions?
Which amino acid is an essential amino acid involved in various metabolic functions?
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What type of amino acids are responsible for producing glucose exclusively?
What type of amino acids are responsible for producing glucose exclusively?
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What type of groups does Coenzyme A transfer?
What type of groups does Coenzyme A transfer?
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Which enzyme is associated with the cofactor Zn++?
Which enzyme is associated with the cofactor Zn++?
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What does NADP+ partially transfer?
What does NADP+ partially transfer?
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Which of the following is an example of absolute specificity in enzymes?
Which of the following is an example of absolute specificity in enzymes?
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Which coenzyme is involved in transferring amino groups?
Which coenzyme is involved in transferring amino groups?
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What is the role of cofactors in enzymatic reactions?
What is the role of cofactors in enzymatic reactions?
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What type of ion is required as a cofactor by pyruvate phosphokinase?
What type of ion is required as a cofactor by pyruvate phosphokinase?
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Which enzyme uses Fe+++ or Fe++ as a cofactor?
Which enzyme uses Fe+++ or Fe++ as a cofactor?
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What is a key difference between enzymes and hormones regarding their site of action?
What is a key difference between enzymes and hormones regarding their site of action?
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In terms of chemical nature, which of the following is classified as a polypeptide or protein hormone?
In terms of chemical nature, which of the following is classified as a polypeptide or protein hormone?
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Which of the following hormones bind to intranuclear receptors?
Which of the following hormones bind to intranuclear receptors?
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What role does cAMP play in the mechanism of action of hormones with extracellular receptors?
What role does cAMP play in the mechanism of action of hormones with extracellular receptors?
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Which type of hormone is known to have receptors located intracytoplasmically?
Which type of hormone is known to have receptors located intracytoplasmically?
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How do hormones that utilize intracellular receptors generally function?
How do hormones that utilize intracellular receptors generally function?
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Which category does melatonin belong to based on its chemical nature?
Which category does melatonin belong to based on its chemical nature?
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What happens upon the binding of a hormone to its extracellular receptor?
What happens upon the binding of a hormone to its extracellular receptor?
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Which hormone specifically acts on muscle and liver, while another acts only on the liver?
Which hormone specifically acts on muscle and liver, while another acts only on the liver?
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What is the final product of cAMP degradation by phosphodiesterase?
What is the final product of cAMP degradation by phosphodiesterase?
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What physiological effect does cAMP NOT stimulate?
What physiological effect does cAMP NOT stimulate?
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Which subunit of the G-protein dissociates to interact with adenylate cyclase?
Which subunit of the G-protein dissociates to interact with adenylate cyclase?
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What type of hormone primarily stimulates the thyroid gland?
What type of hormone primarily stimulates the thyroid gland?
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Which of the following is a function of insulin in relation to cAMP?
Which of the following is a function of insulin in relation to cAMP?
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Which lobe of the pituitary gland is responsible for producing growth hormone?
Which lobe of the pituitary gland is responsible for producing growth hormone?
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How does a neurotransmitter or hormone initiate G-protein action?
How does a neurotransmitter or hormone initiate G-protein action?
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Study Notes
Amino Acids
- 20 different amino acids are essential for human life.
- 12 amino acids can be synthesized by the human body.
- 8 essential amino acids must be obtained from food.
- Amino acids are classified based on their chemical structure and nutritional requirements.
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Chemical Classification:
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Neutral Amino Acids: Contain an equal number of amino and carboxylic groups.
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Aliphatic Amino Acids:
- Glycine, Alanine, Valine, Isoleucine, Leucine
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Hydroxy Amino Acids:
- Serine, Threonine
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Sulphur Amino Acids:
- Cysteine, Cystine, Methionine
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Aromatic Amino Acids:
- Phenylalanine, Tyrosine, Tryptophan
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Aliphatic Amino Acids:
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Basic Amino Acids: Have more amino groups than carboxylic groups.
- Histidine, Arginine, Lysine.
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Acidic Amino Acids: Have more carboxylic groups than amino groups.
- Glutamic acid, Aspartic acid.
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Imino Acids: Contain an imino group (NH).
- Proline, Hydroxyproline.
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Neutral Amino Acids: Contain an equal number of amino and carboxylic groups.
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Nutritional Classification:
-
Essential Amino Acids:
- Cannot be synthesized by the body.
- Must be obtained from diet.
- Deficiency can lead to diseases.
- Examples: Valine, Leucine, Isoleucine, Histidine, Phenylalanine, Tryptophan, Threonine, Methionine.
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Nonessential Amino Acids:
- Synthesized in the body.
- Not essential for dietary intake.
- Includes all other amino acids not classified as essential.
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Essential Amino Acids:
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Metabolic (Biological) Classification:
- Based on the fate of amino acids in the body.
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Glucogenic Amino Acids:
- Converted into glucose.
- All amino acids except leucine are glucogenic.
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Ketogenic Amino Acids:
- Converted into ketone bodies.
- Examples: Leucine and lysine.
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Both Glucogenic and Ketogenic:
- Converted into both glucose and ketone bodies.
- Examples: Tyrosine, Phenylalanine, Tryptophan, Isoleucine.
Proteins
- Definition: Polymers of amino acids linked by peptide bonds.
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Classification of Proteins:
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According to Peptide Bond Structure:
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Simple Proteins:
- Only produce amino acids on hydrolysis.
- Examples:
- Albumin: Found in egg white, serum, and milk.
- Globulin: Found in egg white, serum, and milk.
- Histones: Associated with nucleic acids (chromatin) and in the globin part of hemoglobin.
- Scleroproteins (Albuminoids):
- Keratin: Found in hair, nails, and dermis.
- Elastin: Found in elastic tissues.
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Conjugated Proteins:
- Have a non-protein component called a prosthetic group.
- Examples:
- Phosphoproteins: Contain phosphate groups.
- Lipoproteins: Contain lipids.
- Glycoproteins: Contain carbohydrates.
- Chromoproteins: Contain pigments.
- Nucleoproteins: Contain nucleic acids.
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Simple Proteins:
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According to Function:
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Catalytic Proteins (Enzymes): Act as biochemical catalysts.
- Examples: Glucokinase, Dehydrogenase, Transaminase.
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Defense Proteins: Bind to foreign substances (like bacteria and viruses) to combat invasion.
- Examples: Immunoglobulins.
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Transport Proteins: Bind to small biomolecules and transport them.
- Examples:
- Hemoglobin: Transports oxygen.
- Transferrin: Transports iron.
- Examples:
-
Storage Proteins: Bind and store small molecules for future use.
- Examples:
- Ferritin: Stores iron in the liver.
- Myoglobin: Stores oxygen in muscles.
- Examples:
-
Nutrient Proteins: Important in early life, from embryo to infant.
- Example: Casein in milk.
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Regulatory Proteins: Regulate cellular and physiological activities.
- Example: Insulin.
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Catalytic Proteins (Enzymes): Act as biochemical catalysts.
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According to Peptide Bond Structure:
Coenzymes in Group Transfer Reactions
- Coenzymes are non-protein organic molecules that assist enzymes in their function.
- They are often required for specific reactions.
- Examples of Coenzymes in Group Transfer Reactions:
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Nicotine Adenine Dinucleotide: NAD and NADP
- Functions: Electron (hydrogen atom) carriers in redox reactions.
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Flavin Adenine Dinucleotide: FAD
- Function: Electron (hydrogen atom) carrier in redox reactions.
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Coenzyme A: CoA
- Function: Carries acyl groups.
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Coenzyme Q: CoQ
- Function: Electron (hydrogen atom) carrier in redox reactions.
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Thiamine Pyrophosphate: Vitamin B1
- Function: Handles aldehydes.
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Pyridoxal Phosphate: Vitamin B6
- Function: Handles amino groups.
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Biotin:
- Function: Carries carbon dioxide.
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Cobamide Coenzymes: Vitamin B12
- Function: Carries alkyl groups.
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Nicotine Adenine Dinucleotide: NAD and NADP
Cofactors
- Inorganic substances that are required for, or increase the rate of, catalysis.
- Often metal ions.
- Examples of Enzymes with Metal Ion Cofactors:
- Carbonic Anhydrase: Zn++
- Alcohol Dehydrogenase: Zn++
- Cytochromes, Hemoglobin: Fe+++ or Fe++
- Ferredoxin: Fe+++ or Fe++
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Cytochrome Oxidase: Cu++ or Cu+
- Pyruvate Phosphokinase: K+ and Mg++
Enzyme Specificity
-
Enzymes are highly specific:
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Absolute Specificity: Enzyme acts on only one substrate.
- Examples: Uricase and uric acid, Urease and urea.
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Relative Specificity: Enzyme acts on a group of similar compounds.
- Often targets a specific bond or functional group.
- Stereochemical Specificity: Enzyme distinguishes between stereoisomers.
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Absolute Specificity: Enzyme acts on only one substrate.
Hormonal Action:
-
Hormones are chemical messengers that regulate various bodily processes.
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They differ from enzymes in their site of production and mode of action.
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Classification of Hormones:
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According to Chemical Nature:
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Amino Acid Derivatives:
- Thyroid hormones (T3 and T4)
- Catecholamines (Epinephrine and norepinephrine)
- Melatonin
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Polypeptide or Protein Hormones:
- Hypothalamic, pituitary, parathyroid, and pancreatic hormones.
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Steroid Hormones:
- Adrenocortical hormones
- Calcitriol hormone
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Amino Acid Derivatives:
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According to Location of Receptors:
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Intracellular Receptors (Group I):
- Intracytoplasmic Receptors: Steroid hormones.
- Intranuclear Receptors: Thyroid hormones.
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Extracellular Receptors (Group II):
- Catecholamines, Glucagons, Calcitonin, Pituitary hormones.
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Intracellular Receptors (Group I):
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Mechanisms of Hormone Action:
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Group I: Hormones with Intracellular Receptors:
- Lipophilic (fat-soluble) hormones diffuse through the plasma membrane.
- Bind to high-affinity receptors in the target cell.
- The hormone-receptor complex binds to specific regions of DNA called hormone response elements (HRE).
- This activates gene transcription and mRNA production.
- The mRNA translates to a specific protein (enzyme).
- The new enzyme then activates the metabolic process.
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Group II: Hormones with Extracellular Receptors:
- Water-soluble hormones interact with plasma membrane receptors.
- This interaction can activate or inactivate adenylate cyclase.
- Activation of adenylate cyclase leads to cAMP (cyclic adenosine monophosphate) production from ATP.
- cAMP is considered a second messenger.
- cAMP activates protein kinase, which phosphorylates proteins and elicits physiological effects.
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Examples of Hormones That Activate Adenylate Cyclase:
- Epinephrine, Norepinephrine, Glucagon, Parathyroid Hormone, FSH, LH, ACTH, MSH.
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Effects of cAMP Activation:
- Stimulates glycogenolysis via phosphorylase activation.
- Stimulates lipolysis via lipase activation.
- Inhibits glycogenesis by inhibiting glycogen synthetase.
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G-Proteins and Hormonal Action:
- Hormones bind to the external face of the G-protein coupled receptor.
- The receptor undergoes a conformational change, which is propagated to the G-protein binding site.
- The G-protein binding site binds to the trimeric G-protein (αβγ), causing it to exchange bound GDP for GTP.
- Exchange of GDP to GTP causes the G-protein to dissociate into α-GTP and βγ subunits.
- The α-GTP subunit diffuses across the inner face of the plasma membrane and interacts with adenylate cyclase.
- Adenylate cyclase becomes activated and converts ATP to cAMP as long as α-GTP is bound to it.
- The α-subunit has GTPase activity and eventually hydrolyzes its bound GTP to GDP + Pi.
- The α-subunit then dissociates from adenylate cyclase and diffuses back to re-associate with βγ to form an inactive molecule.
Pituitary Hormones:
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The pituitary gland is often referred to as the "master gland" of the endocrine system because it controls the functions of other endocrine glands.
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It is located at the base of the brain and is connected to the hypothalamus by nerve fibers.
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The pituitary gland has three sections:
- Anterior Lobe (Adenohypophysis)
- Intermediate Lobe (Pars Intermedia)
- Posterior Lobe (Neurohypophysis)
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**Hormones of the Anterior Lobe: **
- Growth Hormone (GH)
- Adrenocorticotropic Hormone (ACTH)
- Thyroid Stimulating Hormone (TSH)
- Follicle-Stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
- Prolactin
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Test your knowledge on amino acids with this quiz! Explore the essential amino acids, their classifications, and the differences between them. Discover how these vital compounds contribute to human health and nutrition.