Medical Biochemistry — BMB 2105 Specialized OmpathStudy

Continued from $1. MEDICAL BIOCHEMISTRY EXAM ANSWERS BMB 2105: BIOCHEMISTRY OF SPECIALIZED TISSUES --- SECTION A - MULTIPLE CHOICE QUESTIONS (30 MARKS) Question 1 What cell protein binds Calcium ions after signal transduction? a) Adenylate cyclase b) Guanylate cyclase c) Calmodulin d) Calsequestrin Answer: c) Calmodulin Explanation: Calmodulin is a calcium-binding messenger protein that binds calcium ions after signal transduction. It undergoes conformational changes upon binding calcium and then activates various target proteins including enzymes and ion channels. --- Question 2 Muscles respond to insulin by: a) Forming more glycogen b) Breaking down glycogen c) Breaking down lipids d) Breaking down amino acids Answer: a) Forming more glycogen Explanation: Insulin promotes anabolic processes in muscle tissue. It activates glycogen synthase and inhibits glycogen phosphorylase, leading to increased glycogen formation and storage in skeletal muscle. --- Question 3 Which of the following processes would you expect to find in a normal person after a meal? a) Enhanced glycogen synthase activity in the liver b) An increased ratio of phosphorylase A to phosphorylase B in the liver c) An increased rate of lactate formation by enterocytes d) Inhibition of glycogen synthase phosphatase activity in the liver Answer: a) Enhanced glycogen synthase activity in the liver Explanation: After a meal, insulin levels rise, promoting glycogen synthesis. Glycogen synthase activity is enhanced through dephosphorylation (activation) to store excess glucose as glycogen in the liver. --- Question 4 A person has just had a nice meal. Which of the following enzymes would you not expect to find in their system? a) Glycogen phosphorylase b) Glycogen synthase c) Lipoprotein lipase d) Acetyl-CoA carboxylase Answer: a) Glycogen phosphorylase Explanation: After a meal, the fed state promotes anabolic processes. Glycogen phosphorylase (which breaks down glycogen) would be inhibited, while glycogen synthase, lipoprotein lipase, and acetyl-CoA carboxylase would be active to promote storage. --- Question 5 Glucagon has the following effect on lipid metabolism in the liver: a) The net synthesis of triacylglycerides is increased b) Hormone-sensitive lipase is activated c) Both glycogen phosphorylase and glycogen synthase are activated but at markedly different rates d) Glycogen phosphorylase is inactivated while glycogen synthase is activated Answer: b) Hormone-sensitive lipase is activated Explanation: Glucagon activates hormone-sensitive lipase through cAMP-dependent protein kinase, promoting lipolysis and fatty acid mobilization during fasting states. --- Question 6 In blood plasma fatty acids circulate: a) In the content of nuclei of plasma lipoprotein particles b) In the content of an outer shell of plasma lipoprotein particles c) In the complex with serum albumin d) Freely without formation of any complexes Answer: c) In the complex with serum albumin Explanation: Free fatty acids in plasma are bound to albumin for transport due to their hydrophobic nature. This binding allows their solubility in the aqueous plasma environment. --- Question 7 Histamine is made by: a) Neutrophils b) Eosinophils c) Basophils d) Monocytes Answer: c) Basophils Explanation: Basophils and mast cells are the primary producers of histamine. They store histamine in granules and release it during allergic reactions and inflammatory responses. --- Question 8 The oxidation of ethanol with acetaldehyde dehydrogenase results in the formation of: a) Acetaldehyde b) NADH₂ c) Acetate d) Pyruvate Answer: c) Acetate Explanation: Acetaldehyde dehydrogenase catalyzes the oxidation of acetaldehyde to acetate, which is the second step in ethanol metabolism. This reaction also produces NADH. --- Question 9 Which of the following reactions is marked as conjugation? a) Attachment of a hydroxyl to a toxic substance b) Attachment of protons and electrons to a toxic substance c) Glucuronidation d) Any reactions of a synthesis Answer: c) Glucuronidation Explanation: Glucuronidation is a classic Phase II conjugation reaction where glucuronic acid is attached to substrates, making them more water-soluble for excretion. --- Question 10 Troponin C is: a) Responsible for the binding of calcium ions b) Responsible for the binding of G-actin c) Responsible for the inhibition of the actin and myosin interaction d) Phosphorylated by cAMP-dependent protein kinase Answer: a) Responsible for the binding of calcium ions Explanation: Troponin C is the calcium-binding subunit of the troponin complex in skeletal muscle. When calcium binds to troponin C, it initiates the conformational changes that allow muscle contraction. --- Question 11 Exocytosis of acetylcholine-containing vesicles in the presynaptic cell is caused by influx of: a) Sodium ions b) Potassium ions c) Chloride ions d) Calcium ions Answer: d) Calcium ions Explanation: Calcium influx through voltage-gated calcium channels triggers the fu