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Quiz Chapter 5: Metabolism and Enzymes

10 questions · Form 4 Biology Bab 5: Metabolism and Enzymes

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. 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
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Answer: B

Rennet contains chymosin, an enzyme that cleaves milk casein proteins to curdle milk into solid curds for cheese making.

2. What happens to an enzyme after it successfully catalyzes a biochemical transformation of a substrate into products?

  1. A. It degrades immediately into free amino acids.
  2. B. It remains chemically unchanged and is free to bind another substrate molecule.
  3. C. It permanently binds to the product molecule.
  4. D. It is converted into energy (ATP).
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Answer: B

Enzymes are catalysts; they emerge from reactions chemically unchanged and can be reused repeatedly in small quantities.

3. Which enzyme is used during the stonewashing process to give denim jeans a faded, soft texture?

  1. A. Cellulase
  2. B. Amylase
  3. C. Lipase
  4. D. Protease
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Answer: A

Cellulase partially digests cellulose fibers on cotton denim surfaces, softening fabric and giving it a stonewashed appearance.

4. Which enzyme is added to biological washing powders to effectively remove blood and egg stains from clothing?

  1. A. Cellulase
  2. B. Amylase
  3. C. Protease
  4. D. Lactase
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Answer: C

Protease breaks down insoluble proteins (found in blood, egg, and gravy) into soluble amino acids or peptides easily washed away.

5. When substrate concentration is increased continuously while keeping enzyme concentration constant, the reaction rate eventually levels off. What is the limiting factor at this plateau (Vmax)?

  1. A. Substrate concentration
  2. B. Enzyme concentration
  3. C. Accumulation of ATP
  4. D. Temperature of the medium
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Answer: B

At Vmax, all enzyme active sites are fully saturated with substrate; thus, enzyme concentration becomes the limiting factor.

6. 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.
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Answer: B

Optimum temperature corresponds to the peak height of the rate curve where kinetic collisions and substrate conversions are maximized.

7. Pepsin operates efficiently in the stomach, while Trypsin functions in the small intestine. What are their optimum pH environments respectively?

  1. A. Pepsin: pH 2.0 | Trypsin: pH 8.5
  2. B. Pepsin: pH 7.0 | Trypsin: pH 2.0
  3. C. Pepsin: pH 8.5 | Trypsin: pH 6.8
  4. D. Pepsin: pH 6.8 | Trypsin: pH 1.5
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Answer: A

Pepsin requires an acidic environment (pH 1.5-2.0) provided by stomach HCl, whereas Trypsin works best in an alkaline environment (pH 8.0-8.5) in the duodenum.

8. 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.
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Answer: B

At freezing temperatures, enzymes have minimal kinetic energy resulting in negligible collisions; however, they are not denatured and regain activity upon warming.

9. 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.
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Answer: B

The precise 3D spatial geometry of an enzyme's active site only fits a specific substrate molecule with a complementary configuration.

10. 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
Show answer

Answer: B

The Lock and Key Hypothesis compares the complementary shape of an enzyme's active site (lock) with its specific substrate (key).

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