MCAT Chem Domain 1: Biochemistry Welcome to your MCAT Chem Domain 1: Biochemistry 1. MCAT Chem: Biochemistry A protein that functions at a pH of 7.4 has an amino acid substitution at a site where the original amino acid was neutral and nonpolar. The substitution is with a residue that is positively charged at physiological pH. How might this substitution affect the protein's function? Increase its catalytic efficiency Disrupt its tertiary structure Enhance its substrate specificity Reduce its allosteric regulation None 2. MCAT Chem: Biochemistry A biochemical pathway is regulated by feedback inhibition. If the end product increases in concentration, what happens to the activity of the pathway's first enzyme? It increases. It decreases. It remains unchanged. It oscillates. None 3. MCAT Chem: Biochemistry If a mutation in the DNA results in the replacement of a hydrophobic amino acid with a hydrophilic amino acid in the transmembrane domain of a protein, what is the most likely effect on the protein's function? Increased protein stability Disrupted membrane anchoring Enhanced signal transduction Improved enzyme kinetics None 4. MCAT Chem: Biochemistry In an enzyme-catalyzed reaction, what would be the effect of doubling the enzyme concentration on the reaction rate in the presence of excess substrate? The reaction rate would double. The reaction rate would remain the same. The reaction rate would increase but not double. The reaction rate would quadruple. None 5. MCAT Chem: Biochemistry A researcher is studying a protein that can undergo phosphorylation. Which amino acid residue in the protein is most likely to be phosphorylated? Valine Alanine Serine Leucine None 6. MCAT Chem: Biochemistry What is the primary structural difference between starch and cellulose? Starch is a polymer of glucose, while cellulose is a polymer of fructose. Starch has ?-1,4-glycosidic bonds, while cellulose has ?-1,4-glycosidic bonds. Starch is branched, while cellulose is linear. Starch is primarily found in animals, while cellulose is found in plants. None 7. MCAT Chem: Biochemistry How does a decrease in pH (increase in H+ concentration) affect the structure of a protein with a high number of aspartic acid and glutamic acid residues? It causes the protein to unfold. It increases the protein's stability. It leads to the formation of more hydrogen bonds. It results in the protonation of these acidic residues, potentially causing conformational changes. None 8. MCAT Chem: Biochemistry A peptide bond forms between which two functional groups in amino acids? Carboxyl group and amino group Carboxyl group and R group Amino group and R group Hydroxyl group and amino group None 9. MCAT Chem: Biochemistry In the context of enzyme kinetics, what is meant by 'substrate saturation'? The point at which increasing substrate concentration no longer increases the rate of reaction. The maximum speed at which an enzyme can catalyze a reaction. The minimum substrate concentration needed for an enzyme to function. The saturation of an enzyme's active site with a competitive inhibitor. None 10. MCAT Chem: Biochemistry Which process describes the conversion of a protein from a higher ordered structure to a random coil or unfolded state? Renaturation Denaturation Polymerization Dephosphorylation None 11. MCAT Chem: Biochemistry If a genetic mutation changes a codon to a stop codon, what is the immediate effect on the polypeptide being synthesized? It will be longer than intended. It will be shorter than intended. It will have an incorrect amino acid sequence. It will be more stable. None 12. MCAT Chem: Biochemistry In an experiment, a scientist observes that upon increasing the salt concentration, a soluble protein precipitates out of solution. What is the likely cause of this phenomenon? Salt-out effect, where high salt concentration disrupts hydrophobic interactions. Enhanced hydrophobic interactions due to the high salt concentration. Disruption of hydrogen bonds between water molecules and the protein. Increased ionic interactions between the protein and salt ions. None 13. MCAT Chem: Biochemistry What is the primary effect of a catalyst on a chemical reaction? It increases the concentration of reactants. It provides an alternative pathway with a lower activation energy. It changes the equilibrium position of the reaction. It increases the temperature of the reaction mixture. None 14. MCAT Chem: Biochemistry A researcher is evaluating a protein that binds to a specific DNA sequence. The protein's binding affinity is significantly reduced after a single amino acid change. Which type of amino acid substitution is most likely to cause this decrease in binding affinity? A polar amino acid replaced with a similar polar amino acid A basic amino acid replaced with another basic amino acid A hydrophobic amino acid replaced with a hydrophilic amino acid A small amino acid replaced with a similarly small amino acid None 15. MCAT Chem: Biochemistry In a redox reaction within a biological system, how is the oxidation state of an atom determined? By the number of protons in the atom compared to its neutral state By assigning electrons to the more electronegative atom in a bond By the number of electrons lost or gained in the reaction By the total number of electrons in the outer orbital of the atom None 16. MCAT Chem: Biochemistry What is the primary role of NAD+ in cellular metabolism? It acts as a direct source of energy for cell activities. It serves as a primary substrate for DNA synthesis. It functions as an electron carrier in redox reactions. It acts as a second messenger in signal transduction pathways. None 17. MCAT Chem: Biochemistry A mutation leads to a change in a single nucleotide of a gene encoding an enzyme, resulting in a premature stop codon. This type of mutation is known as: Missense mutation Nonsense mutation Silent mutation Frameshift mutation None 18. MCAT Chem: Biochemistry Which type of interaction is primarily responsible for the formation of alpha-helices and beta-sheets in proteins? Disulfide bridges Hydrophobic interactions Hydrogen bonding between backbone atoms Ionic interactions between side chains None 19. MCAT Chem: Biochemistry In an aqueous solution, how do amphipathic molecules typically arrange themselves? They form micelles with hydrophobic tails inward and hydrophilic heads outward. They dissolve completely with no distinct arrangement. They associate with each other via their hydrophilic regions only. They precipitate out of the solution to minimize interaction with water. None 20. MCAT Chem: Biochemistry What is the primary structural feature that distinguishes RNA from DNA? RNA is typically double-stranded, whereas DNA is single-stranded. RNA contains uracil, while DNA contains thymine. RNA has a deoxyribose sugar, while DNA has a ribose sugar. RNA nucleotides are larger than DNA nucleotides. None 1 out of 20 Time is Up! Time's up
