BC ADM Fundamentals & Core Concepts 3 — Questions and Answers
Question 1: Which enzyme is responsible for converting proinsulin to insulin in the pancreatic beta cell?
- Carboxypeptidase E only
- Prohormone convertases PC1/3 and PC2 along with carboxypeptidase E (Correct answer)
- Glucokinase
- Dipeptidyl peptidase-4 (DPP-4)
Correct answer: Prohormone convertases PC1/3 and PC2 along with carboxypeptidase E
Proinsulin is cleaved to insulin and C-peptide by prohormone convertases PC1/3 and PC2, with carboxypeptidase E removing residual amino acids.
Question 2: The Somogyi effect refers to which glucose pattern?
- Persistent fasting hyperglycemia due to inadequate basal insulin
- Rebound hyperglycemia following nocturnal hypoglycemia (Correct answer)
- Dawn phenomenon caused by growth hormone surge
- Postprandial hyperglycemia after high-glycemic meals
Correct answer: Rebound hyperglycemia following nocturnal hypoglycemia
The Somogyi effect (rebound hyperglycemia) occurs when nocturnal hypoglycemia triggers counterregulatory hormones, causing morning high glucose.
Question 3: In type 1 diabetes, the autoimmune destruction of beta cells is primarily mediated by which immune mechanism?
- B-cell antibody production alone
- CD8+ cytotoxic T lymphocytes acting directly on beta cells (Correct answer)
- Natural killer cells without T-cell involvement
- Complement activation via the classical pathway
Correct answer: CD8+ cytotoxic T lymphocytes acting directly on beta cells
CD8+ cytotoxic T lymphocytes are the primary effectors of beta-cell destruction in type 1 diabetes, recognizing beta-cell autoantigens presented on MHC class I.
Question 4: Glucokinase (hexokinase IV) acts as the glucose sensor in pancreatic beta cells because it:
- Is saturated at low glucose concentrations
- Has a low Km and high affinity for glucose
- Has a high Km and is not saturated at normal glucose levels (Correct answer)
- Is inhibited by glucose-6-phosphate
Correct answer: Has a high Km and is not saturated at normal glucose levels
Glucokinase has a high Km (~10 mM) so its activity rises proportionally with glucose concentration, allowing beta cells to sense physiologic glucose changes.
Question 5: Which statement best describes C-peptide's clinical utility in diabetes management?
- It directly stimulates insulin receptors and lowers blood glucose
- It measures residual beta-cell function and helps distinguish insulin deficiency types (Correct answer)
- It is a more accurate marker of postprandial glucose excursions than glucose
- It is elevated in all forms of type 2 diabetes regardless of duration
Correct answer: It measures residual beta-cell function and helps distinguish insulin deficiency types
C-peptide is an indirect marker of endogenous insulin secretion, used to assess residual beta-cell function and differentiate type 1 from type 2 diabetes.
Question 6: A patient with a fasting plasma glucose of 118 mg/dL on two separate occasions is classified as having:
- Normal fasting glucose
- Impaired fasting glucose (prediabetes) (Correct answer)
- Type 2 diabetes mellitus
- Secondary diabetes
Correct answer: Impaired fasting glucose (prediabetes)
Impaired fasting glucose (prediabetes) is defined by fasting plasma glucose of 100–125 mg/dL on two occasions per ADA criteria.
Question 7: Which lipoprotein abnormality is most characteristically associated with insulin resistance in type 2 diabetes?
- Elevated LDL-C with large, buoyant LDL particles
- Low HDL-C, elevated triglycerides, and small dense LDL particles (Correct answer)
- Isolated elevation of Lp(a) lipoprotein
- Elevated chylomicrons with normal VLDL
Correct answer: Low HDL-C, elevated triglycerides, and small dense LDL particles
Insulin resistance promotes atherogenic dyslipidemia characterized by elevated triglycerides, low HDL-C, and small dense LDL, increasing cardiovascular risk.
BC ADM Fundamentals & Core Concepts 3
Which enzyme is responsible for converting proinsulin to insulin in the pancreatic beta cell?