MBBS Biochemistry 3

Question 1

Which amino acid is the precursor for catecholamine synthesis (dopamine, norepinephrine, epinephrine)?

Accepted Answer

Phenylalanine/Tyrosine

Answer

Tryptophan

Answer

Histidine

Answer

Glutamate

Question 2

Cystic fibrosis is caused by a defect in which protein?

Accepted Answer

CFTR (Cystic Fibrosis Transmembrane conductance Regulator)

Answer

Spectrin

Answer

Dystrophin

Answer

Collagen type IV

Question 3

Which reaction produces the most ATP per molecule of substrate in cellular respiration?

Accepted Answer

Oxidative phosphorylation via the electron transport chain

Answer

Glycolysis

Answer

Substrate-level phosphorylation in the Krebs cycle

Answer

Beta-oxidation of fatty acids

Question 4

Which cofactor is required for carboxylation reactions in fatty acid synthesis and gluconeogenesis?

Accepted Answer

Biotin

Answer

Thiamine pyrophosphate

Answer

Pyridoxal phosphate

Answer

Lipoic acid

Question 5

In the urea cycle, the final step converts arginine to urea and which other product?

Accepted Answer

Ornithine

Answer

Citrulline

Answer

Aspartate

Answer

Fumarate

Question 6

Alpha-1-antitrypsin deficiency causes emphysema through which mechanism?

Accepted Answer

Unopposed neutrophil elastase activity destroying alveolar walls

Answer

Increased collagen deposition in lung parenchyma

Answer

Impaired surfactant production

Answer

Increased mucus production blocking small airways