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7.2 Insulin Synthesis & Secretion — Test 1
Q1. Conversion of proinsulin to insulin involves removal of the:✓ C-peptide
Q2. Glucose enters the pancreatic beta cell mainly via the transporter:✓ GLUT2
Q3. Inside the beta cell, glucose metabolism raises ATP, which triggers insulin release by:✓ Closing ATP-sensitive K+ channels (depolarizing the cell)
Q4. Sulfonylureas stimulate insulin secretion by:✓ Closing the ATP-sensitive K+ channel
Q5. The insulin receptor is a tetramer with intrinsic activity that is best described as:✓ Tyrosine kinase (two alpha + two beta subunits)
Q6. C-peptide is clinically useful because it:✓ Reflects endogenous insulin (beta-cell) secretion
Q7. Match each component with its role in insulin secretion and choose the correct option.✓ A-ii, B-iii, C-i
Q8. Insulin binding to its receptor causes the immediate event of:✓ Autophosphorylation of tyrosines on the beta subunits
Q9. Insulin increases glucose uptake in muscle and fat by:✓ Translocating GLUT4 transporters to the cell membrane
Q10. A non-functioning K-ATP channel mutation that keeps the channel OPEN would cause:✓ Impaired insulin secretion (the cell cannot depolarize)
Q11. The A and B chains of insulin are linked by:✓ Two interchain disulfide bridges
Q12. GLUT2 in the beta cell is well suited to glucose sensing because it:✓ Is high-capacity and insulin-independent (tracks blood glucose)
Q13. Glucokinase acts as the beta-cell 'glucose sensor' because it:✓ Has a high Km, so its rate tracks physiological glucose levels
Q14. Insulin secretion in response to oral glucose is greater than to IV glucose because of:✓ The incretin effect (gut hormones like GLP-1/GIP)
Q15. Which feature is characteristic of an insulin-secreting (beta) cell?✓ Abundant rough ER and secretory granules storing insulin
Q16. The final trigger for insulin granule exocytosis is:✓ A rise in intracellular Ca2+
Q17. Why does C-peptide measurement remain valid in a patient injecting insulin?✓ Exogenous insulin contains no C-peptide, so C-peptide reflects only endogenous output
Q18. Insulin promotes potassium uptake into cells by stimulating:✓ Na+/K+-ATPase activity
Q19. Drugs that close the K-ATP channel (sulfonylureas) require which to be effective?✓ Functioning beta cells
Q20. The overall sequence of glucose-stimulated insulin secretion is:✓ Glucose -> GLUT2 -> ATP rise -> K-ATP closes -> depolarization -> Ca2+ influx -> exocytosis