Chapter Exam

Chapter 4: Enzymes and Bioenergetics — Online MCQ Test

Q: The energy required to start a chemical reaction is called:

Answer: B. Activation energy — Activation energy is the minimum energy needed for reactants to undergo a chemical reaction.

Q: If the temperature rises beyond the optimum range, enzyme activity usually decreases because:

Answer: B. The enzyme may denature — High temperature can disrupt the enzyme's three-dimensional structure, causing denaturation and loss of activity.

BIOTECHNOLOGY · Grade 11 · CBSE(NCERT)

Practice Chapter 4: Enzymes and Bioenergetics with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 11 BIOTECHNOLOGY. This chapter covers: Enzymes biological catalysts enzyme kinetics activation energy metabolism ATP bioenergetics energy transformation cellular respiration metabolic pathways enzyme activity. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 4: Enzymes and Bioenergetics — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 11 BIOTECHNOLOGY — Chapter 4: Enzymes and Bioenergetics, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the main role of an enzyme in a biochemical reaction?

A. To increase the activation energy
B. To act as a biological catalyst and speed up the reaction ✓
C. To permanently change into the product
D. To provide ATP directly

Answer: B. To act as a biological catalyst and speed up the reaction
Enzymes are biological catalysts that increase the rate of reactions without being consumed. They do this by lowering the activation energy.

The energy required to start a chemical reaction is called:

A. Free energy
B. Activation energy ✓
C. Bond energy
D. Potential energy

Answer: B. Activation energy
Activation energy is the minimum energy needed for reactants to undergo a chemical reaction.

If the temperature rises beyond the optimum range, enzyme activity usually decreases because:

A. The substrate becomes inorganic
B. The enzyme may denature ✓
C. ATP is converted into ADP
D. The enzyme becomes more specific

Answer: B. The enzyme may denature
High temperature can disrupt the enzyme's three-dimensional structure, causing denaturation and loss of activity.

Which graph most likely describes the effect of pH on enzyme activity?

A. A straight line showing continuous increase with pH
B. A bell-shaped curve with maximum activity at an optimum pH ✓
C. A horizontal line with no change in activity
D. A downward line showing activity always decreases as pH increases

Answer: B. A bell-shaped curve with maximum activity at an optimum pH
Most enzymes show maximum activity at an optimum pH and reduced activity on either side of that value.

A student observes that an enzyme works well at 37°C but loses activity rapidly at 70°C. Which conclusion is MOST appropriate?

A. The enzyme is a lipid and melts at high temperature
B. The enzyme has a low substrate concentration at 70°C
C. The enzyme likely denatures at high temperature, altering its active site ✓
D. The enzyme requires more ATP at 70°C

Answer: C. The enzyme likely denatures at high temperature, altering its active site
Enzymes are proteins whose structure is sensitive to heat. At high temperatures, denaturation changes the active site and reduces activity.