Biophysical chemistry – pH, buffers, kinetics, thermodynamics - One Line Questions

1. When the substrate concentration is equal to Km, the reaction velocity (V0) is: — Vmax/2
2. The pH scale typically ranges from: — 0 to 14
3. What is the pH of a 0.01 M solution of hydrochloric acid (HCl)? — 2
4. What is the pOH of a solution with a pH of 9? — 5
5. What is Gibbs free energy (G)? — A measure of the energy available to do work
6. A system at equilibrium has: — Zero net change in reactants and products, and ΔG = 0
7. An exergonic reaction is characterized by: — A negative ΔG and it releases energy
8. An endergonic reaction is characterized by: — A positive ΔG and it absorbs energy
9. A buffer solution resists changes in pH because it contains: — A weak acid and its conjugate base
10. A solution with a pH of 7 is considered: — Neutral
11. A solution with a pH of 3 is: — Acidic
12. The second law of thermodynamics is related to entropy. What does it imply about biological systems? — Biological systems tend towards disorder and require energy input to maintain order
13. What is the effect of pH on enzyme activity? — Each enzyme has an optimal pH range; activity decreases outside this range
14. In biological systems, ATP hydrolysis (ATP → ADP + Pi) is an example of which type of reaction? — Exergonic
15. What does the first law of thermodynamics state? — Energy cannot be created or destroyed, only transformed
16. What is the relationship between enthalpy (H), internal energy (U), pressure (P), and volume (V)? — H = U + PV
17. In biological systems, which of the following is a common buffer system? — Carbonic acid and bicarbonate
18. What is the effect of a competitive inhibitor on the Km and Vmax of an enzyme? — Increases Km, Vmax remains unchanged
19. What is the effect of a non-competitive inhibitor on the Km and Vmax of an enzyme? — Km remains unchanged, decreases Vmax
20. Which of the following is a characteristic of the transition state in a reaction? — It is a high-energy, unstable state
21. Which of the following is a characteristic of a reversible reaction? — It can proceed in both forward and reverse directions
22. Which of the following is NOT a property of a buffer solution? — Its pH is independent of the concentrations of the buffer components
23. In enzyme kinetics, the term 'catalytic efficiency' is often represented by: — kcat/Km
24. What does a steep slope on a Lineweaver-Burk plot indicate? — High Km and low Vmax
25. The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of a weak acid and the ratio of its conjugate base to acid. Which of the following is the correct form of the equation? — pH = pKa + log([A-]/[HA])
26. The buffering capacity of a buffer is highest when: — pH = pKa
27. Which of the following is an example of a buffer system in red blood cells? — Phosphate buffer system
28. The kinetic energy of molecules is directly proportional to: — Absolute temperature
29. When a strong acid is added to a buffer solution, the buffer works by: — Reacting the acid with the conjugate base component
30. The term 'allosteric regulation' refers to: — Regulation of enzyme activity by binding to a site distant from the active site
31. In thermodynamics, an adiabatic process is one where: — No heat is exchanged with the surroundings
32. In enzyme kinetics, the Lineweaver-Burk plot (double reciprocal plot) is used to determine: — Km and Vmax
33. According to the laws of thermodynamics, which of the following is true for a spontaneous process? — The change in Gibbs free energy (ΔG) is always negative
34. In the context of biophysical chemistry, what is pH a measure of? — The concentration of hydronium ions (protons)
35. The activation energy of a reaction is: — The energy required to reach the transition state
36. According to the third law of thermodynamics: — The entropy of a perfect crystal at absolute zero is zero
37. The 'active site' of an enzyme is where: — The substrate binds and catalysis occurs
38. Competitive inhibition of an enzyme occurs when: — The inhibitor increases the Km but does not affect Vmax
39. The Michaelis-Menten model of enzyme kinetics describes the relationship between the initial reaction velocity (V0) and the substrate concentration ([S]). What is Vmax in this model? — The maximum velocity when the enzyme is saturated with substrate
40. What does the term 'turnover number' refer to in enzyme kinetics? — The number of substrate molecules converted to product per enzyme molecule per unit time when the enzyme is saturated
41. What does the pKa value represent for a weak acid? — Both B and C
42. What is the effect of increasing temperature on the rate of most enzyme-catalyzed reactions? — The rate increases up to an optimal temperature, then decreases
43. Which of the following statements best describes the concept of enzyme kinetics? — The study of the rates of enzyme-catalyzed reactions
44. What is the Michaelis constant (Km) in enzyme kinetics? — The substrate concentration at which the reaction rate is half of Vmax
45. What is the role of a catalyst in a chemical reaction? — To decrease the activation energy
46. What is the primary function of a buffer solution in a biological system? — To maintain a stable pH despite the addition of acids or bases
47. What is the primary role of the bicarbonate buffer system in blood? — To maintain blood pH within a narrow range
48. The concept of 'coupled reactions' in biochemistry involves: — An endergonic reaction driven by an exergonic reaction
49. Non-competitive inhibition of an enzyme typically affects: — Vmax only
50. The equilibrium constant (Keq) for a reaction is related to the change in Gibbs free energy (ΔG) by the equation: — ΔG = -RT ln(Keq)
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