Question 1

Which of the following best describes the difference between anabolic and catabolic reactions in metabolism?

Accepted Answer

Anabolic reactions build complex molecules from simpler ones, requiring energy input, while catabolic reactions break down large molecules into smaller ones, releasing energy.

Question 2

Which statement about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is due to the complementary fit between the enzyme's active site and its substrate in terms of shape, size, charge, and orientation.

Question 3

Which of the following best explains how enzymes lower the activation energy ($$E_A) of a $$reaction?

Accepted Answer

By providing a microenvironment that promotes the formation of the transition state and stabilizing it.

Question 4

A scientist measures the rate of an enzyme-catalyzed reaction by monitoring the disappearance of substrate over time. Which experimental method is most appropriate for this measurement?

Accepted Answer

Measuring the decrease in absorbance of a starch-iodine solution in the presence of amylase.

Question 5

Which of the following statements about the Michaelis constant ($$K_m) is $$correct?

Accepted Answer

$$K_m is $$the substrate concentration at which the reaction rate is half of $$V_{max}.$$

Question 6

What is the effect of increasing substrate concentration on the rate of an enzyme-catalyzed reaction when all enzyme active sites are saturated?

Accepted Answer

The rate of reaction remains constant at its maximum value ($$V_{max}).$$

Question 7

Which of the following best describes the role of a coenzyme in enzyme activity?

Accepted Answer

A coenzyme is an organic molecule that binds loosely to the enzyme and is required for its activity.

Question 8

Which of the following changes would most likely result in the denaturation of an enzyme?

Accepted Answer

A drastic increase in temperature above the enzyme's optimum.

Question 9

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to the active site, preventing substrate binding, and increasing $$K_m$$ without affecting $$V_{max}.$$

Question 10

Which of the following is true about non-competitive inhibition?

Accepted Answer

Non-competitive inhibitors decrease $$V_{max}$$ but do not change $$K_m.$$

Question 11

Which of the following best explains why enzymes are effective in small amounts?

Accepted Answer

Enzymes have high turnover rates, allowing them to catalyze many reactions without being changed.

Question 12

Which of the following scenarios best illustrates allosteric regulation?

Accepted Answer

An inhibitor binds to a regulatory site on a multi-subunit enzyme, stabilizing the inactive form and reducing enzyme activity.

Question 13

Which of the following is an example of feedback inhibition in a metabolic pathway?

Accepted Answer

The accumulation of ATP inhibits phosphofructokinase, slowing down glycolysis.

Question 14

Which of the following best describes the induced fit hypothesis of enzyme action?

Accepted Answer

The active site changes shape upon substrate binding, resulting in a precise fit that facilitates catalysis.

Question 15

Which of the following experimental designs would best allow you to determine the effect of pH on enzyme activity?

Accepted Answer

Vary the pH of the reaction mixture while keeping temperature, substrate, and enzyme concentrations constant, and measure the initial rate of product formation.

Question 16

Which of the following is a correct statement about irreversible enzyme inhibition?

Accepted Answer

Irreversible inhibitors form strong covalent bonds with enzymes, permanently inactivating them.

Question 17

A patient is exposed to cyanide, which acts as a non-competitive inhibitor of cytochrome oxidase. What is the most likely effect on cellular respiration?

Accepted Answer

Cellular respiration will be inhibited because cyanide decreases the number of functional enzymes, lowering $$V_{max}.$$

Question 18

Which of the following best explains why restoring the pH to the optimum level can often restore enzyme activity after a slight deviation?

Accepted Answer

pH changes are usually reversible within limits, allowing the enzyme's ionic and hydrogen bonds to reform and restore the active site's shape.

Comprehensive Study Notes on Enzymes

Study Guide - Practice Questions

Study Guide - Flashcards