Medical Biochemistry II: Biochemical OmpathStudy

Examination 2021/2022 Bachelor of Medicine and Bachelor of Surgery Paper C Unit Code: MBMB2200 Unit Title: Medical Biochemistry II(MBMB2212: Biochemical Endocrinology, MBMB2234: Neurochemistry) Date: Fri 28th Jan, 2022 Time: 2.00 PM – 4.00 PM (2 Hours) Department of Medical Biochemistry, Medical School --- 1. All of the following are substrates and products of the reaction catalyzed by phosphatidylinositol 3-kinase EXCEPT: A) Phosphatidylinositol bisphosphate is a substrate B) Inositol trisphosphate is a substrate C) ATP is a substrate D) Phosphatidylinositol trisphosphate is a product E) ADP is a product Answer: B) Inositol trisphosphate is a substrate Explanation: PI3K phosphorylates phosphatidylinositol bisphosphate (PIP2) to generate PIP3 using ATP. Inositol trisphosphate (IP3) is not a substrate; it is generated by PLC, not PI3K. --- 2. The major difference between hormones with intracellular receptors and those with cell membrane receptors is that the former tend to be: A) Larger B) Charged C) Amino acid derivatives D) Proteins E) Hydrophobic Answer: E) Hydrophobic Explanation: Hormones with intracellular receptors (e.g., steroids, thyroid hormones) are hydrophobic and can cross cell membranes. --- 3. Many hormones like insulin, glucagon, and epinephrine: A) Can only regulate key enzymes in metabolic pathways B) Can only regulate transcription factors C) Can regulate key enzymes and transcription factors D) Only regulate amino acid synthesis pathways E) All of the above Answer: C) Can regulate key enzymes and transcription factors Explanation: These hormones regulate metabolism both at enzymatic levels and through gene expression changes. --- 4. Which hormone fits this description? "Affects metabolism, essential for CNS development, bone growth, and stored extracellularly." A) Cortisol B) Growth hormone C) T4/T3 D) Thyrocalcitonin E) Leptin Answer: C) T4/T3 Explanation: Thyroid hormones (T4/T3) influence metabolism, CNS maturation, and bone development; T4 is stored in the thyroid colloid. --- 5. Calcium/Phosphate levels in blood are regulated by: A) Aldosterone B) Cortisol C) Prolactin D) ACTH E) PTH and Calcitonin Answer: E) PTH and Calcitonin Explanation: Parathyroid hormone (PTH) increases blood calcium; calcitonin reduces it. --- 6. Glucocorticoids are produced in the: A) Adenohypophysis B) Neurohypophysis C) Pancreas D) Testes/ovaries E) None of the above Answer: E) None of the above Explanation: Glucocorticoids are produced in the adrenal cortex (specifically the zona fasciculata). --- 7. The hormone primarily responsible for glucose storage as glycogen, fat storage, and protein synthesis is: A) Glucagon B) GHC) TSH D) Insulin E) Cortisol Answer: D) Insulin Explanation: Insulin promotes anabolic processes such as glycogenesis, lipogenesis, and protein synthesis. --- 8. Cyclic AMP is best matched with: A) Steroid hormones B) Protein hormones C) Muscle cells D) Testosterone E) None of the above Answer: B) Protein hormones Explanation: Many protein hormones signal via cAMP second messenger (e.g., glucagon, ACTH). --- 9. Classical endocrine glands (e.g., pituitary, thyroid): A) Have ducts B) Are under-regulated C) Produce many products D) Produce hormones E) Use products locally Answer: D) Produce hormones Explanation: Endocrine glands are ductless and release hormones into circulation. --- 10. Iodine uptake and thyroid growth are stimulated by: A) TSH-RH B) TSH C) T3D) Thyroglobulin E) LH Answer: B) TSH Explanation: Thyroid-stimulating hormone (TSH) increases iodine uptake and thyroid cell proliferation. --- 11. The primary effect of T3 and T4 is to: A) Decrease blood glucose B) Promote calcitonin release C) Promote heat-generating (metabolic) reactions D) Stimulate iodine uptake by the thyroid E) All of the above Answer: C) Promote heat-generating (metabolic) reactions --- 12. The primary effect of calcitonin is to: A) Increase blood glucose B) Decrease blood glucose C) Increase calcium excretion in urine D) Increase blood calcium E) Decrease blood calcium (blocks bone release) Answer: E) Decrease blood calcium (blocks bone release) --- 13. Increased blood glucose and anti-inflammatory effects are key actions of: A) Epinephrine B) Glucagon C) Cortisol D) Insulin E) ADH Answer: C) Cortisol --- 14. The primary target of glucagon is the: A) Liver B) Hypothalamus C) Adrenal cortex D) Pancreas E) Kidney Answer: A) Liver --- 15. The endocrine portion of the pancreas is the: A) Adrenal cortex B) Adrenal medulla C) Anterior pituitary D) Posterior pituitary E) Islets of Langerhans Answer: E) Islets of Langerhans --- 16. When a hormone uses a second messenger, the next step after binding is: A) Phosphodiesterase activation B) Protein kinase formation C) Nuclear gene activation D) Adenylyl cyclase activation by G-protein E) Opening of voltage-gated ion channels Answer: D) Adenylyl cyclase activation by G-protein --- 17. A steroid hormone binding to its receptor: A) Forms cAMP B) Converts to cholesterol (sec