Question 1

Which of the following best describes the difference between anabolic and catabolic reactions in metabolism, as illustrated in the provided diagram?

Accepted Answer

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

Question 2

Which statement about the active site of an enzyme is correct based on the diagrams and study materials?

Accepted Answer

The active site is formed by specific amino acids and can change shape to fit the substrate, as described by the induced fit hypothesis.

Question 3

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

Accepted Answer

Enzymes have high turnover rates, meaning a single enzyme molecule can catalyze many reactions per second without being changed.

Question 4

A scientist is measuring the rate of an enzyme-catalyzed reaction by tracking the disappearance of starch using amylase and iodine. Which experimental method is most appropriate?

Accepted Answer

Measuring the absorbance of the reaction mixture at fixed intervals using a colorimeter.

Question 5

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is due to the complementary shape, size, charge, and orientation of the active site to the substrate.

Question 6

Which of the following best describes the effect of a competitive inhibitor on enzyme kinetics?

Accepted Answer

It increases $$K_m$$ but does not affect $$V_{max}.$$

Question 7

A patient is poisoned with cyanide, which acts as a non-competitive inhibitor of cytochrome oxidase. What is the expected effect on enzyme kinetics?

Accepted Answer

$$K_m$$ remains unchanged and $$V_{max}$$ decreases.

Question 8

Which of the following is a correct statement about the role of cofactors in enzyme activity?

Accepted Answer

Cofactors can be inorganic ions, coenzymes, or prosthetic groups, and are required for enzyme activity.

Question 9

Which of the following best explains why enzyme-catalyzed reactions plateau at high substrate concentrations?

Accepted Answer

All active sites of the enzyme are saturated with substrate, so increasing substrate concentration further does not increase the rate.

Question 10

Which of the following is a real-life example of feedback inhibition in cellular metabolism?

Accepted Answer

ATP acts as an allosteric inhibitor of phosphofructokinase in glycolysis, slowing down ATP production when ATP levels are high.

Question 11

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

Accepted Answer

The enzyme's active site changes shape to fit the substrate more precisely upon binding, facilitating catalysis.

Question 12

Which of the following experimental results would indicate that an enzyme is functioning at its optimum temperature?

Accepted Answer

The rate of product formation is at its maximum and does not increase with further temperature increase.

Question 13

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 14

A laboratory experiment shows that increasing enzyme concentration increases the reaction rate only up to a certain point, after which the rate plateaus. What is the most likely explanation?

Accepted Answer

The substrate concentration becomes limiting, so not all enzyme active sites are occupied.

Question 15

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

Accepted Answer

Enzymes provide an alternative reaction pathway by stabilizing the transition state and bringing reactants into close proximity and correct orientation.

Question 16

Which of the following is a correct statement about allosteric regulation of enzymes?

Accepted Answer

Allosteric regulators bind to a site other than the active site, causing a conformational change that can either inhibit or activate the enzyme.

Question 17

Which of the following best describes the effect of pH on enzyme activity?

Accepted Answer

Each enzyme has an optimum pH, and deviations from this pH can reduce activity by altering the charge and conformation of the active site.

Question 18

Which of the following is an example of an irreversible inhibitor?

Accepted Answer

Heavy metals such as mercury binding to enzymes and disrupting disulfide bonds.

Question 19

Which of the following best describes cooperativity in enzyme regulation?

Accepted Answer

The binding of one substrate molecule to an active site increases the affinity of other subunits for additional substrate molecules.

Comprehensive Study Notes on Enzymes

Study Guide - Practice Questions

Study Guide - Flashcards