Biology 9th Chap 7 : Topic 2 - Maryam Publications

Biology Chapter 7 : Topic 2

Enzymes and Their Characteristics

1 / 15

Which statement best defines an enzyme?

A) A mineral required for growth

B) A hormone that controls body functions

C) A nutrient that provides energy to cells

D) A protein that speeds up chemical reactions without being consumed

2 / 15

Why are enzymes called biological catalysts?

A) They provide energy to reactions.

B) They increase the rate of reactions without being used up.

C) They are produced only by plants.

D) They stop unwanted reactions.

3 / 15

Which of the following is a characteristic of enzymes?

A) They are highly specific in their action.

B) They work equally well at all temperatures.

C) They can catalyze every type of reaction.

D) They are consumed during reactions.

4 / 15

An enzyme acts only on a particular substrate because of its:

A) Color

B) Solubility in water

C) Specific three-dimensional shape

D) Large size

5 / 15

Which statement provides evidence that enzymes are proteins?

A) They contain carbon.

B) They become denatured at very high temperatures.

C) They are produced by living cells.

D) They speed up reactions.

6 / 15

A student heats an enzyme solution to 90°C. What is the most likely effect?

A) The enzyme is denatured and loses activity.

B) The enzyme reproduces rapidly.

C) The enzyme becomes more active permanently.

D) The enzyme changes into a substrate.

7 / 15

Which characteristic allows a small amount of enzyme to be used repeatedly?

A) Enzymes are living cells.

B) Enzymes provide energy.

C) Enzymes continuously reproduce.

D) Enzymes are not changed permanently during reactions.

8 / 15

What happens when the pH becomes extremely unsuitable for an enzyme?

A) The enzyme increases its activity indefinitely.

B) The enzyme forms new substrates.

C) The enzyme becomes a hormone.

D) The enzyme may become denatured.

9 / 15

Which statement correctly describes enzyme specificity?

A) An enzyme acts on a particular substrate only.

B) Every substrate can fit into any enzyme.

C) One enzyme can catalyze all metabolic reactions.

D) Enzymes work without substrates.

10 / 15

Why are enzymes important for living organisms?

A) They replace nutrients.

B) They provide oxygen for respiration.

C) They speed up biochemical reactions necessary for life.

D) They store genetic information.

11 / 15

Which factor directly affects enzyme activity?

A) All of the above

B) Temperature

C) pH

D) Substrate concentration

12 / 15

If the concentration of substrate increases while enzyme concentration remains constant, the reaction rate will initially:

A) Stop completely

B) Remain unchanged

C) Increase

D) Decrease

13 / 15

Which statement best explains why enzymes are efficient catalysts?

A) They provide ATP directly.

B) They lower the activation energy required for reactions.

C) They change into products.

D) They increase the activation energy of reactions.

14 / 15

A digestive enzyme that breaks down starch will not normally digest proteins because enzymes are:

A) Reusable

B) Organic compounds

C) Soluble

D) Specific in action

15 / 15

Which statement summarizes the characteristics of enzymes most accurately?

A) Enzymes are protein catalysts that are specific, reusable, and affected by temperature and pH.

B) Enzymes provide energy for all cellular activities.

C) Enzymes are non-protein substances that are consumed during reactions.

D) Enzymes work only outside living organisms.

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