MCAT Bio Domain 1: Biochemistry Welcome to your MCAT Bio Domain 1: Biochemistry 1. MCAT Bio: Biochemistry What is the primary structure determinant for the specificity of protein kinase A 'PKA' for its substrates? Hydrophobic interaction with the substrate's secondary structure Hydrogen bonding with the substrate's alpha helices Phosphorylation at serine or threonine residues adjacent to a basic amino acid Ionic bonding with the substrate's carboxyl groups None 2. MCAT Bio: Biochemistry In the context of enzyme kinetics, what effect does increasing substrate concentration have on Vmax and Km in a reaction following Michaelis-Menten kinetics? Increases Vmax; decreases Km Increases Vmax; no effect on Km No effect on Vmax; increases Km No effect on Vmax; no effect on Km None 3. MCAT Bio: Biochemistry Which of the following best describes the role of chaperone proteins in protein folding? They permanently bind to proteins to maintain their structure. They facilitate the correct folding pathway or the refolding of misfolded proteins. They prevent the synthesis of proteins that are prone to misfolding. They degrade misfolded proteins before they can aggregate. None 4. MCAT Bio: Biochemistry What is the primary function of the enzyme telomerase in eukaryotic cells? To repair damaged DNA To replicate mitochondrial DNA To extend the telomeres of chromosomes To enhance the transcription of genes None 5. MCAT Bio: Biochemistry In the context of signal transduction, what role do G-protein coupled receptors (GPCRs) play when they are activated? They directly phosphorylate target proteins. They open ion channels in the cell membrane. They activate a G-protein by exchanging GDP for GTP. They increase the permeability of the cell membrane to ions. None 6. MCAT Bio: Biochemistry Which of the following is a characteristic feature of lysosomal enzymes? They have a high pH optimum. They are only active outside the cell. They require metal ions as cofactors. They have a low pH optimum. None 7. MCAT Bio: Biochemistry How does the structure of fibrous proteins differ from that of globular proteins? Fibrous proteins are primarily composed of beta sheets, while globular proteins are composed of alpha helices. Fibrous proteins exhibit a spherical shape, while globular proteins are more elongated and strand-like. Fibrous proteins are composed of long, linear polypeptide chains, while globular proteins are compact and folded. Fibrous proteins are insoluble in water, while globular proteins are not. None 8. MCAT Bio: Biochemistry What is the primary role of NAD+ in cellular metabolism? To serve as a primary substrate for ATP synthesis To act as a second messenger in signal transduction To function as an electron carrier in redox reactions To facilitate the transport of glucose into cells None 9. MCAT Bio: Biochemistry In the lac operon, what is the role of the allolactose molecule? It binds to the repressor, preventing it from binding to the operator. It binds to RNA polymerase, enhancing its binding to the promoter. It acts as a corepressor, facilitating the binding of the repressor to the operator. It increases the degradation rate of the repressor protein. None 10. MCAT Bio: Biochemistry Which of the following enzymes is responsible for unwinding the DNA double helix during replication? DNA polymerase DNA ligase Helicase Topoisomerase None 11. MCAT Bio: Biochemistry What is the role of ubiquitin in protein degradation? It folds misfolded proteins for refolding. It marks proteins for degradation by the proteasome. It acts as a chaperone to prevent protein aggregation. It stabilizes proteins by preventing their unfolding. None 12. MCAT Bio: Biochemistry During muscle contraction, what role does calcium ion (Ca2+) play? It binds to myosin, allowing it to attach to actin. It binds to troponin, causing a conformational change that moves tropomyosin. It activates ATPase activity in myosin for energy release. It forms cross-bridges between actin and myosin filaments. None 13. MCAT Bio: Biochemistry In the electron transport chain, what is the final electron acceptor? Oxygen NAD+ FAD ATP None 14. MCAT Bio: Biochemistry What is the effect of a competitive inhibitor on the Km and Vmax of an enzyme-catalyzed reaction? Increases Km; no effect on Vmax No effect on Km; decreases Vmax Increases Km; decreases Vmax No effect on Km; increases Vmax None 15. MCAT Bio: Biochemistry What role does the enzyme acetyl-CoA carboxylase play in fatty acid metabolism? It catalyzes the rate-limiting step in fatty acid synthesis. It is involved in the beta-oxidation of fatty acids. It activates fatty acids for transport across the mitochondrial membrane. It catalyzes the cleavage of fatty acids into acetyl-CoA. None 16. MCAT Bio: Biochemistry In the context of DNA repair, what is the primary function of the enzyme DNA ligase? To remove incorrect nucleotides To unwind the DNA helix To fill in missing nucleotides To join Okazaki fragments None 17. MCAT Bio: Biochemistry What is the primary structural difference between starch and cellulose? Starch is a linear polymer, while cellulose is branched. Starch is composed of alpha-glucose, while cellulose is composed of beta-glucose. Starch contains nitrogen, while cellulose does not. Cellulose is a linear polymer, while starch is branched. None 18. MCAT Bio: Biochemistry What is the role of peptidyl transferase during protein synthesis? It catalyzes the addition of amino acids to the growing polypeptide chain. It recognizes and binds to the mRNA codon. It assists in the proper folding of the new protein. It transports tRNA to the ribosome. None 19. MCAT Bio: Biochemistry How does the structure of RNA differ from that of DNA? RNA contains thymine instead of uracil. RNA is double-stranded, while DNA is single-stranded. RNA has a ribose sugar, while DNA has a deoxyribose sugar. DNA is more stable under alkaline conditions than RNA. None 20. MCAT Bio: Biochemistry Which of the following is true about the structure of hemoglobin compared to myoglobin? Hemoglobin has a higher affinity for oxygen than myoglobin. Hemoglobin is a single polypeptide, while myoglobin is quaternary. Hemoglobin exhibits cooperative binding of oxygen, while myoglobin does not. Myoglobin stores oxygen in muscle cells, while hemoglobin does not store oxygen. None 1 out of 20 Time is Up! Time's up
