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(Biological and Biochemical) Flashcards

7 cards from real MCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which enzyme catalyzes the committed step of glycolysis?

    Answer: Phosphofructokinase-1

    Phosphofructokinase-1 (PFK-1) catalyzes the irreversible conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, which is the committed and rate-limiting step of glycolysis.

  2. During oxidative phosphorylation, where do electrons from NADH ultimately transfer?

    Answer: Molecular oxygen

    Electrons from NADH pass through the electron transport chain and are ultimately accepted by molecular oxygen (O2), which is reduced to water (H2O).

  3. Which type of RNA carries the genetic code from the nucleus to the ribosome for translation?

    Answer: mRNA

    Messenger RNA (mRNA) carries the genetic information transcribed from DNA and serves as the template for protein synthesis at the ribosome.

  4. A mutation that converts a codon from UAU (Tyr) to UAA results in what type of mutation?

    Answer: Nonsense mutation

    UAA is a stop codon; converting an amino acid codon to a stop codon creates a nonsense mutation that causes premature termination of translation.

  5. Which bond connects amino acids in a polypeptide chain?

    Answer: Peptide bond

    A peptide bond is a covalent amide bond formed between the carboxyl group of one amino acid and the amino group of the next during translation.

  6. Which organelle is responsible for modifying, sorting, and packaging proteins for secretion?

    Answer: Golgi apparatus

    The Golgi apparatus receives proteins from the ER, modifies them (e.g., glycosylation), and sorts them into vesicles destined for the cell membrane, lysosomes, or secretion.

  7. In the citric acid cycle, how many NADH molecules are produced per acetyl-CoA?

    Answer: 3

    Each turn of the citric acid cycle produces 3 NADH molecules (at the isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase steps).