AAMC MCAT Exam 4 QUESTIONS AND ANSWERS RATED A+ 2023|2024

AAMC MCAT Exam 4 QUESTIONS AND ANSWERS RATED A+ 2023|2024 Most cytochrome P450 enzymes alter the activity of drugs by: A. phosphorylating them. B. dephosphorylating them. C. oxidizing them. D. reducing them. - ANSWER C. oxidizing them. cytochrome p450 acts as monooxygenase, where an oxygen atom is inseted into substrate, thereby resulting in oxidation of substrate. Given that antibiotics like erythromycin are metabolized by estrogen-sensitive P450 enzymes within the liver, which graph best predicts the expected relative half-life of erythromycin in adult males versus adult females? - ANSWER A This is the only graph that correctly illustrates a quicker metabolism—or shorter half- life—of erythromycin in females. Given the continuous presence of GH in females, the cytochrome P450 enzymes are up-regulated, resulting in more rapid metabolism of certain drugs (like erythromycin). As a result, the half-life of erythromycin is expected to be lower in females (in other words, it would take less time to metabolize the drug due to the greater presence of P450 enzymes). The researchers want to generate a mutant mouse strain that expresses a constantly active variant of ACC2 by replacing the amino acid at position 212 with a different residue. Which residue is the best choice as a replacement? A. Tyrosine B. Serine C. Alanine D. Threonine - ANSWER C. Alanine According to the passage, AMPK inactivates ACC2 through phosphorylation of the residue at position 212. To create a constitutively active variant, the residue at position 212 should be substituted with a residue that cannot be phosphorylated. Of all the amino acids listed, only alanine cannot be phosphorylated