Quiz Chapter 5: Metabolism and Enzymes

1. Non-protein chemical compounds or inorganic ions that bind to enzymes to help them function properly are known as:

1. A. Inhibitors
2. B. Substrates
3. C. Cofactors
4. D. Polypeptides

2. Which statement correctly describes a reversible enzyme-catalyzed reaction?

1. A. The enzyme can only catalyze forward reactions under all circumstances.
2. B. The enzyme can catalyze both forward and reverse reactions depending on substrate and product concentrations.
3. C. The enzyme converts products into ATP energy.
4. D. The reaction can proceed without needing activation energy.

3. At 0°C, what is the status of enzyme activity in living cells?

1. A. Enzymes are completely denatured and permanently inactive.
2. B. Enzymes are inactive due to very low kinetic energy, but remain undamaged.
3. C. Enzymes work at their maximum catalytic rate.
4. D. Active sites undergo structural conformational expansion.

4. Which hypothesis is commonly used to illustrate the mechanism of substrate binding to an enzyme's active site?

1. A. Fluid Mosaic Model
2. B. Lock and Key Hypothesis
3. C. Sliding Filament Theory
4. D. Cohesion-Tension Theory

5. What happens to the structure and function of a human enzyme when heated above 60°C?

1. A. Its kinetic energy drops to zero, temporarily halting activity.
2. B. It becomes denatured as high temperatures disrupt its 3D active site shape.
3. C. It speeds up the reaction exponentially without stopping.
4. D. It converts into a cofactor to assist other enzymes.

6. Why are enzymes described as 'specific' in their action?

1. A. They only operate at one exact temperature value.
2. B. Their active site shape complements only one specific type of substrate.
3. C. They can only be synthesized by specialized stomach cells.
4. D. They are destroyed after catalyzing a single chemical reaction.

7. During cheese production, which enzyme causes milk proteins (casein) to coagulate into solid curds?

1. A. Lipase
2. B. Rennet (Chymosin)
3. C. Maltase
4. D. Zymase

8. Which graph characteristic represents the optimum temperature of an enzyme-catalyzed reaction?

1. A. The lowest point on the temperature curve.
2. B. The peak point on the curve where the reaction rate is at its maximum.
3. C. The flat linear region where the rate remains zero.
4. D. The point where the enzyme begins to denature.

9. Which statement correctly describes an anabolic pathway in living cells?

1. A. Breakdown of complex molecules into simple units, releasing energy.
2. B. Synthesis of complex molecules from simpler precursors, requiring energy.
3. C. Chemical reactions that occur exclusively outside living cells.
4. D. Transport of water across cell membranes down a concentration gradient.

10. Why does changing the pH away from an enzyme's optimum value decrease its catalytic activity?

1. A. It reduces the concentration of substrate molecules.
2. B. It alters ionic charges on the active site, breaking ionic and hydrogen bonds.
3. C. It consumes all ATP present in the reaction medium.
4. D. It converts the enzyme from a protein into a carbohydrate.