MCAT Biochemistry Practice Test 12: Bioenergetics and Regulation of Metabolism

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1. Adding heat to a closed biological system will do all of the following EXCEPT:

  • A. increase the internal energy of the system.
  • B. increase the average of the vibrational, rotational, and translational energies.
  • C. cause the system to do work to maintain a fixed internal energy.
  • D. increase the enthalpy of the system.

2. At 25°C the ΔG° for a certain reaction A → B + 2 C is 0. If the concentration of A, B, and C in the cell at 25°C are all 10 mM, how does the ΔG compare to the measurement taken with 1 M concentrations?

  • A. ΔG is greater than ΔG°, thus the reaction is spontaneous.
  • B. ΔG is less than ΔG°, thus the reaction is spontaneous.
  • C. ΔG is greater than ΔG°, thus the reaction is nonspontaneous.
  • D. ΔG is less than ΔG°, thus the reaction is nonspontaneous.

3. Which of the following statements is true about the hydrolysis of ATP?

  • A. The free energy of ATP hydrolysis is independent of pH.
  • B. One mole of creatine phosphate can phosphorylate two moles of ADP.
  • C. The free energy of hydrolysis of ATP is nearly the same as for ADP.
  • D. ATP yields cyclic AMP after two hydrolysis reactions.

4. The reduction half-reaction in the last step of the electron transport chain is:

  • A. O2 + 4 e + 4 H+ → 2 H2O
  • B. NADPH → NADP+ + e + H+
  • C. NADP+ + e + H+ → NADPH
  • D. Ubiquinone (Q) → Ubiquinol (QH2)

5. The ability to exist in both an oxidized and a reduced state is characteristic of:

  • A. adenosine triphosphate (ATP).
  • B. electron carriers.
  • C. regulatory enzymes.
  • D. peptide hormones.

6. What energy state was described in the introduction to this chapter?

  • A. Absorptive
  • B. Postabsorptive
  • C. Starvation
  • D. Vegetative

7. With prolonged fasting, the brain can turn to which alternative fuel for energy?

  • A. Fructose
  • B. Lactate
  • C. Ketone bodies
  • D. Fatty acids

8. How do hormonal controls of glycogen metabolism differ from allosteric controls?

  • A. Hormonal control is systemic and covalent.
  • B. Hormonal control is local and covalent.
  • C. Hormonal control is systemic and noncovalent.
  • D. Hormonal control is local and noncovalent.

9. Which of the following tissues is most dependent on insulin?

  • A. Active skeletal muscle
  • B. Resting skeletal muscle
  • C. Cardiac muscle
  • D. Smooth muscle

10. Glucocorticoids have been implicated in stress-related weight gain because:

  • A. they increase appetite and decrease satiety signals.
  • B. they increase the activity of catabolic hormones.
  • C. they increase glucose levels, which causes insulin secretion.
  • D. they interfere with activity of the leptin receptor.

11. In the absence of oxygen, which tissue will experience damage most rapidly?

  • A. Skin
  • B. Brain
  • C. Red blood cells
  • D. Liver

12. A respiratory quotient approaching 0.7 indicates metabolism primarily of which macromolecule?

  • A. Carbohydrates
  • B. Lipids
  • C. Nucleic acids
  • D. Amino acids

13. Which of the following side effects would be anticipated in someone taking leptin to promote weight loss?

  • A. Drowsiness
  • B. Increased appetite
  • C. Irritability
  • D. Fever

14. Which of the following statements is FALSE?

  • A. Growth hormone participates in glucose counter-regulation.
  • B. T4 acts more slowly than T3.
  • C. ATP stores are turned over more than 10,000 times daily.
  • D. Catecholamines stimulate the sympathetic nervous system.

15. Which process is expected to begin earliest in a prolonged fast?

  • A. Ketone bodies are used by the brain.
  • B. Glycogen storage is halted.
  • C. Proteins are broken down.
  • D. Enzyme phosphorylation and dephosphorylation.