BI3.1-6 | Chemistry and Metabolism of Carbohydrates — Practice Quiz — BI3.1-6 | Chemistry and Metabolism of Carbohydrates

Q1 BI3.1 1 pt

Glycogen is the storage form of glucose in animal tissues. Compared to amylopectin (the branched component of starch), glycogen is:

A Less branched, with α-1,4 bonds only

B More branched, with branch points every 8-12 residues ✓

C Unbranched, consisting entirely of α-1,4 bonds like amylose

D Composed of β-1,4 bonds like cellulose

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Q2 BI3.2 1 pt

Glucose uptake into skeletal muscle and adipose tissue requires the insulin-dependent glucose transporter GLUT-4. In the absence of insulin signalling, GLUT-4 is:

A Permanently expressed on the cell surface but inactive

B Sequestered in intracellular vesicles, unable to reach the plasma membrane ✓

C Degraded in lysosomes and must be re-synthesised

D Exported from the cell into the extracellular space

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Q3 BI3.2 1 pt

A village health worker is preparing ORS (Oral Rehydration Salts) for a child with cholera. The effectiveness of ORS depends on the co-transport of glucose and sodium in the intestine. This co-transport is mediated by which transporter?

A GLUT-2 on the basolateral membrane

B GLUT-5 on the luminal membrane

C SGLT-1 on the luminal membrane ✓

D GLUT-4 on the luminal membrane

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Q4 BI3.3 1 pt

Phosphofructokinase-1 (PFK-1) catalyses the committed step of glycolysis. Which of the following is the most potent allosteric ACTIVATOR of PFK-1?

A ATP

B Citrate

C Fructose-2,6-bisphosphate ✓

D Glucagon

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Q5 BI3.3 1 pt

Red blood cells lack mitochondria and therefore cannot perform the TCA cycle or oxidative phosphorylation. The total number of ATP molecules produced per glucose molecule in an RBC is:

A 30-32 ATP

B 2 ATP ✓

C 8 ATP

D 0 ATP (RBCs don't produce ATP)

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Q6 BI3.3 1 pt

A patient in septic shock has a blood lactate level of 9 mmol/L (normal: 0.5-1.5 mmol/L). The elevated lactate is a direct consequence of tissues being forced to rely on which metabolic process due to inadequate oxygen delivery?

A Gluconeogenesis

B Aerobic glycolysis followed by the TCA cycle

C Anaerobic glycolysis with conversion of pyruvate to lactate ✓

D The pentose phosphate pathway (HMP shunt)

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Q7 BI3.3 1 pt

During prolonged fasting, the liver synthesises glucose through gluconeogenesis. Which of the following statements about gluconeogenesis is CORRECT?

A Fatty acids are a major precursor for glucose synthesis

B Skeletal muscle can release free glucose into the blood via gluconeogenesis

C The rate-limiting bypass enzyme is fructose-1,6-bisphosphatase

D Lactate, glycerol, and glucogenic amino acids are the main precursors ✓

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Q8 BI3.4 1 pt

A 55-year-old diabetic patient develops bilateral cataracts. The lens opacification is caused by osmotic damage from the accumulation of which sugar alcohol, produced from glucose by the enzyme aldose reductase?

A Fructose

B Galactitol

C Sorbitol ✓

D Mannitol

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Q9 BI3.5 1 pt

A 22-year-old Type 1 diabetic is brought to the emergency department with Kussmaul breathing, fruity breath odour, blood glucose of 450 mg/dL, and arterial pH of 7.1. A 65-year-old Type 2 diabetic presents with blood glucose of 650 mg/dL, severe dehydration, and altered consciousness but NO ketoacidosis. What BEST explains the absence of significant ketosis in the Type 2 patient?

A Type 2 diabetics have adequate hepatic glycogen to prevent ketogenesis

B Type 2 diabetics have enough residual insulin to suppress lipolysis and ketogenesis, even though it's insufficient for glucose uptake ✓

C Type 2 diabetics do not have insulin resistance in adipose tissue

D Ketone bodies are produced but rapidly cleared by the kidneys in Type 2 diabetes

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Q10 BI3.6 1 pt

A patient's HbA1c is reported as 9.2% (target: <7%). The HbA1c reflects average blood glucose control over approximately which time period?

A The past 1-2 weeks

B The past 2-3 months ✓

C The past 6-12 months

D The fasting state only (past 8-12 hours)

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