Question 1

Which of the following best describes the function of enzymes in biological systems?

Accepted Answer

Enzymes lower the activation energy, speeding up chemical reactions.

Question 2

A student is investigating the effect of temperature on enzyme activity. Which graph would best represent the rate of reaction as temperature increases from 0°C to 60°C?

Accepted Answer

A curve that rises to a peak and then falls sharply after a certain temperature.

Question 3

Given the equation for enzyme-catalyzed reactions: $$E + S \rightarrow ES \rightarrow E + P$$, what does 'ES' represent?

Accepted Answer

The enzyme-substrate complex.

Question 4

If an enzyme is denatured by high temperature, what is the most likely effect on its activity?

Accepted Answer

Its activity will decrease or stop completely.

Question 5

Which of the following is a correct statement about the specificity of enzymes?

Accepted Answer

Enzymes are specific to their substrates due to the shape of their active site.

Question 6

A researcher adds a competitive inhibitor to an enzyme reaction. What is the expected effect?

Accepted Answer

The inhibitor binds to the enzyme's active site, reducing substrate binding.

Question 7

Which equation best represents the relationship between enzyme, substrate, and product?

Accepted Answer

$$E + S \rightarrow ES \rightarrow E + P$$

Question 8

In a laboratory experiment, a student observes that increasing substrate concentration increases the rate of reaction up to a point, after which the rate levels off. What is the best explanation for this observation?

Accepted Answer

All enzyme active sites are occupied, so the reaction rate cannot increase further.

Question 9

Which of the following would most likely decrease the rate of an enzyme-catalyzed reaction?

Accepted Answer

Adding a non-competitive inhibitor.

Question 10

A patient has a genetic mutation that alters the shape of an enzyme's active site. What is the most likely consequence?

Accepted Answer

The enzyme will not bind its substrate effectively, reducing reaction rate.

Question 11

Which of the following best explains why enzymes are reusable in biological reactions?

Accepted Answer

Enzymes are not changed or consumed during the reaction.

Question 12

A scientist is studying the effect of pH on enzyme activity. At which pH would you expect pepsin, a stomach enzyme, to be most active?

Accepted Answer

pH 2

Question 13

Which of the following is NOT a factor that affects enzyme activity?

Accepted Answer

Color of the enzyme

Question 14

A student mixes an enzyme with its substrate and measures the rate of product formation. Which variable should be kept constant to ensure valid results?

Accepted Answer

Temperature

Question 15

Which of the following best describes the lock-and-key model of enzyme action?

Accepted Answer

The enzyme's active site fits the substrate exactly, like a key fits a lock.

Question 16

If the following reaction occurs in a cell: $$C_6H_{12}O_6$ + 6O_2 ightarrow 6CO_2 + 6H_2O + 	ext{energy}$$, which process is being described?

Accepted Answer

Cellular respiration

Question 17

A biologist observes that an enzyme works best at 37°C but loses activity at 60°C. What is the most likely reason?

Accepted Answer

The enzyme denatures at high temperature.

Question 18

Which of the following is a multi-step process involving enzymes in the human body?

Accepted Answer

Digestion of starch into glucose

Question 19

A student adds more enzyme to a reaction mixture and observes an increase in reaction rate. What is the best explanation?

Accepted Answer

More enzyme molecules mean more active sites for substrate binding.

Question 20

Which of the following statements about enzyme inhibitors is correct?

Accepted Answer

Non-competitive inhibitors bind to a site other than the active site, changing enzyme shape.

Membrane Transport and Diffusion in Cells

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