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Bioenergetics and Oxidative Phosphorylation MCQs

57 MCQs with clinical pearls · MBBS Biochemistry · Prof Jariya

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Topics covered (5)

Sample MCQs with clinical pearls

Which of the following vitamins acts as a component of the mitochondrial respiratory chain?
A) Biotin
B) Cyanocobalamin
C) Folic acid
D) Nicotinamide ✔
E) Retinal
NICOTINAMIDE (vitamin B3/niacin) → NAD⁺ (nicotinamide adenine dinucleotide) = essential respiratory chain coenzyme. NAD⁺ accepts electrons from TCA cycle substrates → NADH → Complex I substrate. RIBOFLAVIN (vitamin B2) → FAD and FMN — also respiratory chain components. BIOTIN = CO₂ fixation (pyruvate carboxylase, ACC). CYANOCOBALAMIN (B12) = methyl transfer reactions. RETINAL = visual cycle. FOLIC ACID = one-carbon transfer. 📹 [VIDEO LINK]
NAD is derived from which of the following vitamins?
A) Biotin
B) Niacin ✔
C) Pyridoxine
D) Riboflavin
E) Thiamine
NAD (nicotinamide adenine dinucleotide) is derived from NIACIN (NICOTINAMIDE/NICOTINIC ACID, vitamin B3). Can also be synthesised from TRYPTOPHAN (60mg tryptophan = 1mg niacin). RIBOFLAVIN (B2) → FAD and FMN. THIAMINE (B1) → TPP. PYRIDOXINE (B6) → PLP. BIOTIN (B7) → CO₂ fixation. Deficiency of niacin → PELLAGRA (dermatitis, diarrhoea, dementia). 📹 [VIDEO LINK]
NADH derived from glycolysis in the heart is transferred to the mitochondria in which of the following forms?
A) Alpha-ketoglutarate
B) Aspartate
C) Glutamate
D) Malate ✔
E) Oxaloacetate
MALATE-ASPARTATE SHUTTLE (heart, liver, kidney): cytosolic NADH → malate dehydrogenase → OAA reduced to MALATE → MALATE transferred into mitochondria via malate-alpha-KG antiporter → oxidised back to OAA → generates MITOCHONDRIAL NADH → Complex I → 2.5 ATP per cytosolic NADH. This shuttle delivers the full NADH equivalent — highest ATP yield. 📹 [VIDEO LINK]

These are three of 57 MCQs in this section. Every question carries a clinical pearl explaining the reasoning.

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