Molecular cell biology Final ALL VERSIONS 2025 | LATEST AND ACCURATE REAL EXAM QUESTIONS WITH DETAILED ANSWERS | VERIFIED FOR GUARANTEED PASS | LATEST UPDATE

1. ________ link multiple sugars in a chain to form polysaccharides. o A) Peptide bonds o B) Hydrogen bonds o C) Glycosidic bonds o D) Ionic bonds o Answer: C) Glycosidic bonds ▪ Rationale: Glycosidic bonds link monosaccharides (sugars) to form polysaccharides like starch and cellulose. 2. The ultimate source of chemical energy for all cells is: o A) Glucose o B) Oxygen o C) Light o D) ATP o Answer: C) Light ▪ Rationale: Light is the ultimate source of energy for most living organisms through the process of photosynthesis. 3. Which type of biological macromolecule does not participate in polymerization reactions? o A) Nucleic acids o B) Carbohydrates o C) Lipids o D) Proteins o Answer: C) Lipids ▪ Rationale: Lipids do not participate in polymerization as they are not made up of repeating monomer units like nucleic acids, carbohydrates, and proteins. 4. Covalent bonds between which of the following pairs of atoms are polar? o A) C-H o B) C-C o C) O-H o D) N-H o Answer: C) O-H ▪ Rationale: The O-H bond is polar due to the significant electronegativity difference between oxygen and hydrogen. 5. Monomeric proteins do not contain a: o A) Primary structure o B) Secondary structure o C) Tertiary structure o D) Quaternary structure o Answer: D) Quaternary structure ▪ Rationale: Monomeric proteins only have primary, secondary, and tertiary structures; quaternary structure involves multiple protein subunits. 6. Synthesis of ATP: o A) Is only carried out in the mitochondria o B) Requires oxygen o C) Occurs only during aerobic respiration o D) None of the above o Answer: D) None of the above ▪ Rationale: ATP can be synthesized through various pathways like glycolysis, oxidative phosphorylation, and fermentation, depending on the conditions. 7. An EF-hand, also known as helix-loop-helix, is an example of: o A) Domain o B) Motif o C) Alpha-helix o D) Protein complex o Answer: B) Motif ▪ Rationale: An EF-hand is a common structural motif found in proteins that bind calcium. 8. What is the y-intercept of a Lineweaver-Burk plot? o A) 1/[S] o B) Km o C) 1/Vmax o D) Vmax o Answer: C) 1/Vmax ▪ Rationale: The y-intercept of a Lineweaver-Burk plot is the reciprocal of Vmax. 9. Which of the following correctly depicts the polarity properties of a water molecule? o A) Water has no polarity o B) Water has non-polar covalent bonds o C) Water has covalent bonds between O-H o D) Water is a hydrophobic molecule o Answer: C) Water has covalent bonds between O-H ▪ Rationale: Water molecules have polar covalent bonds between oxygen and hydrogen, leading to water's unique properties. 10. Which of the following arrow points to the peptide bond? • A) C=O bonded to O-H • B) N-H bonded to O • C) C=O bonded to N-H • D) N-H bonded to N-H • Answer: C) C=O bonded to N-H o Rationale: The peptide bond is formed between the carbonyl group (C=O) and the amine group (N-H). 11. Which of the following terms would accurately describe the molecule below? • A) Hydrophilic • B) Hydrophobic • C) Amphipathic • D) Polar • Answer: C) Amphipathic o Rationale: Amphipathic molecules have both hydrophilic and hydrophobic regions, like phospholipids. 12. Which of the following is true for chaperone molecules? • A) They help in protein degradation • B) They assist in protein folding • C) They increase the rate of denaturation • D) All of the above • Answer: D) All of the above o Rationale: Chaperone molecules help proteins fold correctly and can also assist in degrading misfolded proteins. 13. The G°' of a reaction is -250 kcal/mol. Which of the following can be deduced about this reaction? • A) Keq > 1 • B) Keq < 1 • C) Keq = 1 • D) The reaction is at equilibrium • Answer: B) Keq < 1 o Rationale: A negative G°' indicates a spontaneous reaction, and Keq < 1 indicates the reaction favors products. 14. Which of the amino acids would be best fit for the binding site of trypsin? • A) Aspartate • B) Glutamate • C) Lysine • D) Arginine • Answer: D) Arginine o Rationale: Trypsin cleaves peptide bonds after arginine or lysine residues. 15. Select the true statement regarding enzymes: • A) Enzymes cannot affect the change of free energy • B) Enzymes lower activation energy • C) Enzymes increase the reaction rate • D) Both A) and C) • Answer: D) Both A) and C) o Rationale: Enzymes do not change the free energy but increase the reaction rate by lowering the activation energy. 16. A protein that is able to interact with 4 different ligands (A, B, C, and D) was analyzed, and the Kd value for each ligand is given below. Which ligand would have the weakest interaction with this protein? • A) Ligand A = 10^-11 M • B) Ligand B = 10^-6 M • C) Ligand C = 10^-9 M • D) Ligand D = 10^-12 M • Answer: B) Ligand B = 10^-6 M o Rationale: The higher the Kd value, the weaker the binding affinity, so Ligand B with the highest Kd has the weakest interaction. 17. Which of the following is false of glucose? • A) It is a monosaccharide • B) It is an aldose • C) It is a reducing sugar • D) It is the sugar found in RNA • Answer: D) It is the sugar found in RNA o Rationale: RNA contains ribose, not glucose. 18. Which of the following would decrease the Vmax of a reaction? • A) Increase the number of substrates • B) Decrease the number of enzymes • C) Increase the concentration of enzyme • D) Add a competitive inhibitor • Answer: B) Decrease the number of enzymes o Rationale: Vmax depends on enzyme concentration, so reducing the number of enzymes lowers the Vmax. 19. Which of the following belongs to kinetic energy? • A) Chemical bonds • B) Gravitational potential energy • C) Thermal • D) Nuclear energy • Answer: C) Thermal o Rationale: Thermal energy, related to the motion of atoms and molecules, is a form of kinetic energy. 20. Which of the following statements is true regarding α-helix? • A) It is stabilized by peptide bonds • B) It is an example of a β-sheet structure • C) It is always right-handed • D) Carbonyl oxygen atom is hydrogen bonded to the amide-associated H four residues down the chain • Answer: D) Carbonyl oxygen atom is hydrogen bonded to the amide-associated H four residues down the chain o Rationale: In the α-helix structure, the carbonyl oxygen forms a hydrogen bond with the amide hydrogen four residues down the chain.