BIOCHEMISTRY in Questions and Answers - Alimov A.M. - 2016

SECTION 4. HORMONES

Question 1. What are Hormones?

Answer: Hormones are chemical substances secreted into the Blood by Endocrine glands that affect The rate of metabolic processes in target Cells

Question 2. Which glands belong to the Endocrine System?

Answer: Pineal Gland; Hypothalamus; Pituitary Gland; Thyroid Gland; Parathyroid glands; Thymus; Pancreas; Adrenal Glands; Gonads

Question 3. What are target cells?

Ответ. Target cells are cells that contain receptor Proteins for the specific binding of a particular hormone

Question 4. What is the Chemical Nature of hormones?

Ответ: By their chemical nature, they are classified into:

1. Peptide Hormones (releasing and inhibiting factors, oxytocin, vasopressin)

2. Polypeptides (Glucagon, Calcitonin)

3. Proteins (tropic hormones, parathyroid hormone, Insulin)

4. Amino Acid Derivatives (melatonin, adrenaline, THYROID HORMONES)

5. Steroids (cortisol, aldosterone, testosterone, estradiol)

Question 5. How are hormones classified according to their signal Transduction mechanism in The Cell?

Answer: 1. Hormones that transmit signals via intracellular receptors and regulate the rate of METABOLISM/31.html">Transcription and Translation in target cells

2. Hormones that interact with Membrane Receptors and trigger The production of intracellular second messengers (cAMP)

Question 6. What is The sequence of events during hormonal signal transduction via intracellular receptors?

Ответ: 1. The hormone freely crosses The cell membrane into the cell

2. In the Cytosol, the hormone binds to a receptor protein

3. The hormone-receptor complex enters The Nucleus and interacts with a regulatory Gene

4. Transcription of the gene is either switched on or switched off

5. Multiple mRNA molecules are produced for enzyme synthesis, or transcription ceases

6. Numerous enzyme molecules are synthesized, or their synthesis stops

7. The rate of metabolic processes in the cell changes

Question 7. What is the sequence of events during the transmission of a hormonal signal via membrane receptors?

Answer: 1. The hormone binds to a receptor On the surface of the cell membrane

2. A secondary messenger of the hormone (cAMP) is formed in the cytosol

3. The corresponding protein kinase is activated

4. Key metabolic Enzymes undergo phosphorylation

5. The activity of these enzymes changes, and consequently, the rate of metabolic processes in the cell

Question 8. What substances can act as secondary messengers of hormones?

Answer: 1. Cyclic NUCLEOTIDES: 3', 5'-cyclic adenosine monophosphate (cAMP) and 3', 5'-cyclic guanosine monophosphate (cGMP)

2. Inositol trisphosphate (IP₃) and diacylglycerol (DAG)

3. Calcium Ions

Question 9. How is 3', 5-cAMP formed?

Answer: The binding of a hormone to a membrane receptor alters the conformation of its constituent G-protein, leading to the activation of the enzyme adenylate kinase, which produces 3', 5-cAMP

Question 10. Which enzyme is involved in The breakdown of 3', 5-cAMP?

Answer: Phosphodiesterase catalyzes the Cleavage of the ester bond between the 3'-hydroxyl group of ribose and the OH-group of phosphoric acid in the 3', 5-cAMP molecule, resulting in The formation of AMP

Question 11. What is the result of an increased calcium concentration in the cytosol?

Answer: 1. Ca²⁺ ions, together with DAG, activate protein kinase C located on the inner surface of the cell membrane, which phosphorylates specific intracellular enzymes and alters their activity

2. Calcium ions, in a complex with the cytosolic protein calmodulin, activate certain enzymes, notably Ca²⁺-calmodulin-dependent protein Kinases

Question 12. What is The Structure of the insulin receptor?

Answer: It is composed of two α-subunits and two β-subunits linked by Disulfide Bonds. The α-subunits are located on the outer side of the Cell Membrane and function to bind insulin. The β-subunits are transmembrane proteins

Question 13. How does the insulin receptor function?

Answer: The N-terminal domains of the α-subunits bind insulin, which leads to a conformational change and triggers Tyrosine kinase activity in the β-subunits. The β-subunits, autophosphorylated at tyrosine residues, initiate a phosphorylation cascade of intracellular proteins that acquire protein kinase activity and phosphorylate Key Enzymes of metabolic processes

Question 14. Which hormone is produced in the pineal gland?

Answer: Melatonin, a Tryptophan derivative

Question 15. What is The Physiological Role of melatonin?

Answer: It inhibits the synthesis of gonadotropins in the pituitary gland, regulates circadian rhythms, etc.

Question 16. Which hormones are produced in the hypothalamus?

Answer. 1. Liberins and statins are regulatory Peptides controlling the secretion of pituitary tropic hormones

2. Vasopressin and Oxytocin

Question 17: What is The Effect of liberins?

Answer: Liberins promote the secretion of Pituitary Hormones

Question 18. What types of liberins exist?

Answer: Somatoliberin, corticoliberin, thyroliberin, folliberin, luliberin, melanoliberin, prolactoliberin

Question 19. What is the effect of statins?

Answer: Statins inhibit the secretion of tropic hormones in the pituitary gland

Question 20. What types of statins exist?

Answer: Somatostatin, prolactostatin, melanostatin

Question 21. Which hormones are produced in the anterior pituitary?

Answer: Somatotropin, corticotropin, thyrotropin, follitropin, prolactin, melanotropin

Question 22. What is the function of tropic hormones?

Answer. 1. They regulate hormone production in endocrine glands controlled by the pituitary

2. They provide a link between the Central Nervous system and the endocrine glands

Question 23. Which hormones are synthesized in The Thyroid Gland?

Answer: 1. Triiodothyronines (T₃)

2. Tetraiodothyronine, or thyroxine (T₄)

3. Calcitonin

Question 24. What are the BIOLOGICAL EFFECTS OF iodine-containing hormones?

Answer: 1. They induce the synthesis of 100 enzymes, primarily oxidoreductases

2. They trigger the mobilization of Glycogen into glucose and the breakdown of triacylglycerols

3. They enhance heat production

4. They exhibit a proliferative effect

Question 25. Which hormone is secreted by the C-Cells of the thyroid gland?

Answer: Calcitonin

Question 26. Where are the receptors for calcitonin located?

Answer: In osteoclasts

Question 27. What is the biological action of calcitonin?

Answer: 1. It inhibits bone resorption, leading to a decrease in Blood Plasma levels of calcium and inorganic phosphate

2. It enhances Collagen synthesis in mineralized Tissues, creating a matrix for mineralization

Question 28. Which hormone of the parathyroid glands do you know?

Answer: Parathyroid hormone (PTH)

Question 29. In the membranes of which cells are the parathyroid Hormone Receptors located?

Answer: On osteoblasts and in Kidney cells

Question 30. How does parathyroid hormone act?

Answer: 1. Acting on osteoblasts, parathyroid hormone induces the release of osteoclast-activating factor and the formation of osteoclasts, which destroy Bone tissue

2. It decreases phosphate reabsorption in the Kidneys

Question 31. Which hormones are secreted by the pancreas?

Answer: 1. Insulin

2. Glucagon

3. Somatostatin

4. Pancreatic Polypeptide Question 32. What is the structure of insulin?

Answer. Insulin is a protein consisting of two chains: chain A (21 Amino Acids) and chain B (30 amino acids), connected by disulfide bridges

Question 33. Which metabolic processes does insulin regulate?

Answer: 1. It increases the permeability of cell membranes to glucose, amino acids, and calcium

2. It activates hexokinase, key enzymes of Glycolysis, dehydrogenases of The Tricarboxylic Acid Cycle and the Pentose Phosphate Pathway, and reductases of fatty acid synthesis

3. It inhibits glycogen phosphorolysis, lipolysis, and Gluconeogenesis

Question 34. Which hormones are synthesized in the adrenal glands?

Answer: 1. In the medulla - adrenaline

2. In the cortex - glucocorticoids, mineralocorticoids, and Sex Hormones

Question 35. What are the main hormones synthesized in the adrenal cortex?

Answer: 1. Glucocorticoids - cortisol and corticosterone

2. Mineralocorticoids - aldosterone

Question 36. What are the metabolic effects of glucocorticoids?

Answer: 1. In skeletal Muscles, lymphoid, and Connective Tissues, they suppress Protein Synthesis AND promote the release of free amino acids into the blood

2. In the Liver, they induce the synthesis of key gluconeogenic enzymes that catalyze The conversion of amino acids into glucose

3. They suppress Immunity, inflammatory responses, and allergic reactions

4. They inhibit collagen Synthesis and Secretion by fibroblasts, which is one of the causes of increased bone resorption - Osteoporosis

Question 37. What is the biological effect of aldosterone?

Answer: It increases the reabsorption of sodium ions and Water in the renal tubules

Question 35. Which hormones are produced by the female gonads?

Answer: 1. Estrogens - estradiol and estriol

2. Progestins - progesterone

Question 39. Which hormones are produced by the male gonads?

Answer: Androgens - testosterone, dihydrotestosterone

Question 40. What are the Physiological effects of androgens?

Answer: Androgens are involved in: 1. Sexual Differentiation and The Development of secondary sexual characteristics

2. Spermatogenesis

3. Male-typical behavior

4. Growth of The Musculoskeletal System

5. Induction of the synthesis of tissue Respiration and lipolysis enzymes

Question 41. What are the physiological effects of estrogens?

Answer: Estrogens regulate: 1. Sexual differentiation

2. Development of secondary sex characteristics

3. Ovulation

4. GROWTH AND DEVELOPMENT of Cartilage

5. Synthesis of Proteins and Enzymes involved in glycolysis, The pentose phosphate pathway, and Lipogenesis

Question 42. Which hormones increase blood glucose levels?

Answer: 1. Epinephrine

2. Glucagon

3. Glucocorticoids

Question 43. Which hormone decreases blood glucose levels?

Answer: Insulin

Question 44. Which hormones enhance proteolysis (protein breakdown) in tissues?

Answer: 1. Thyroxine

2. Glucocorticoids

Question 45. Which hormones stimulate lipolysis (fat breakdown) in tissues?

Answer: 1. Epinephrine

2. Glucagon

3. Thyroxine

4. Growth Hormone

5. Androgens

Question 46. Which hormones enhance lipogenesis?

Answer: 1. Insulin

2. Estrogens

Question 47. Which diseases are caused by hypothyroidism?

Answer: Hypothyroidism in childhood leads to cretinism, whereas in adulthood it results in Myxedema

Question 48. What disorders are caused by growth hormone hypersecretion?

In children – gigantism, in adults – acromegaly

Question 49. What are the clinical signs of hyperthyroidism?

Answer: 1. Exophthalmos (bulging eyes)

2. Tachycardia (elevated Heart rate)

3. Cachexia (wasting syndrome)

4. Hyperthermia (elevated body Temperature)

5. Muscle weakness, increased fatigue

6. Elevated blood serum urea levels

Question 50. What are the signs of adrenal cortex hyperfunction?

Answer: Hypercorticism is characterized by hyperglycemia, ketonemia, and osteoporosis