AAMC MCAT Biological and Biochemical Foundations 1 — Questions and Answers
Question 1: Which enzyme catalyzes the rate-limiting step of glycolysis?
- Phosphofructokinase-1 (PFK-1) (Correct answer)
- Hexokinase
- Pyruvate kinase
- Aldolase
Correct answer: Phosphofructokinase-1 (PFK-1)
PFK-1 catalyzes the irreversible conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, the committed rate-limiting step of glycolysis.
Question 2: What is the net ATP yield from the complete oxidation of one glucose molecule?
- 30-32 ATP (Correct answer)
- 2 ATP
- 38 ATP
- 4 ATP
Correct answer: 30-32 ATP
Complete oxidation yields approximately 30-32 ATP, accounting for the inefficiency of the mitochondrial proton gradient.
Question 3: Which RNA molecule carries amino acids to the ribosome during translation?
- tRNA (Correct answer)
- mRNA
- rRNA
- snRNA
Correct answer: tRNA
Transfer RNA (tRNA) carries specific amino acids and matches its anticodon to the mRNA codon at the ribosome.
Question 4: In competitive enzyme inhibition, what happens to Vmax and Km?
- Vmax unchanged, Km increases (Correct answer)
- Vmax decreases, Km unchanged
- Both decrease
- Both increase
Correct answer: Vmax unchanged, Km increases
Competitive inhibitors bind the active site reversibly, raising apparent Km without changing Vmax since high substrate can outcompete the inhibitor.
Question 5: Which organelle is responsible for post-translational protein modification and sorting?
- Golgi apparatus (Correct answer)
- Smooth ER
- Nucleus
- Peroxisome
Correct answer: Golgi apparatus
The Golgi apparatus modifies, packages, and sorts proteins from the rough ER for secretion or delivery to other organelles.
Question 6: What defines the primary structure of a protein?
- Sequence of amino acids linked by peptide bonds (Correct answer)
- Alpha helices and beta sheets
- 3D folded conformation
- Multiple polypeptide chain assembly
Correct answer: Sequence of amino acids linked by peptide bonds
Primary structure is the linear sequence of amino acids connected by peptide bonds, which dictates all higher-order structure.
AAMC MCAT Biological and Biochemical Foundations 1
Which enzyme catalyzes the rate-limiting step of glycolysis?