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 role of cofactors in enzyme activity is correct, based on the holoenzyme diagram?

Accepted Answer

A holoenzyme is formed when an apoenzyme binds to its cofactor, enabling substrate binding and catalysis.

Question 3

Which property of enzymes allows them to catalyze reactions at low concentrations, as seen with catalase breaking down hydrogen peroxide?

Accepted Answer

Enzymes have high turnover rates, allowing a small amount to catalyze many reactions.

Question 4

Which of the following best explains enzyme specificity?

Accepted Answer

The active site of an enzyme is complementary to its substrate in shape, size, charge, and orientation.

Question 5

Which hypothesis is supported by the observation that some enzymes change shape upon substrate binding, as shown in the induced fit model?

Accepted Answer

Induced fit hypothesis

Question 6

How do enzymes lower the activation energy ($$E_A) of a $$reaction, as shown in the energy profile diagrams?

Accepted Answer

By providing an alternative pathway that stabilizes the transition state.

Question 7

In an experiment measuring the rate of catalase activity by the volume of oxygen produced, which variable should be kept constant to ensure valid results?

Accepted Answer

The temperature, pH, and enzyme concentration, except for the variable being tested.

Question 8

What does a low Michaelis constant ($$K_m) $$indicate about an enzyme's affinity for its substrate?

Accepted Answer

The enzyme has a high affinity for its substrate and reacts readily at low substrate concentrations.

Question 9

Which of the following best describes the effect of increasing substrate concentration on enzyme activity, as shown in enzyme kinetics graphs?

Accepted Answer

The rate of reaction increases and then plateaus when all active sites are saturated.

Question 10

A student adds more enzyme to a reaction mixture with excess substrate. What is the expected effect on the rate of product formation?

Accepted Answer

The rate will increase proportionally until substrate becomes limiting.

Question 11

Why does enzyme activity decrease sharply at temperatures above the optimum, as shown in the temperature-activity graph?

Accepted Answer

The enzyme's three-dimensional structure is disrupted, causing denaturation and loss of active site specificity.

Question 12

Which of the following statements about the effect of pH on enzyme activity is correct?

Accepted Answer

A drastic change in pH can disrupt ionic and hydrogen bonds, denaturing the enzyme.

Question 13

Which of the following best describes competitive inhibition?

Accepted Answer

The inhibitor is structurally similar to the substrate and competes for the active site.

Question 14

How does non-competitive inhibition affect the maximum velocity ($$V_{max}) $$and Michaelis constant ($$K_m) of an $$enzyme-catalyzed reaction?

Accepted Answer

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

Question 15

Which of the following is an example of irreversible enzyme inhibition?

Accepted Answer

Cyanide inhibition of cytochrome oxidase.

Question 16

Which statement best describes allosteric regulation of enzymes?

Accepted Answer

Allosteric regulators bind to a site other than the active site, causing reversible changes in enzyme activity.

Question 17

In feedback inhibition, how does the end product of a metabolic pathway regulate the pathway?

Accepted Answer

It binds allosterically to an enzyme early in the pathway, inhibiting its activity.

Question 18

Which of the following best explains the concept of cooperativity in multi-subunit enzymes?

Accepted Answer

Binding of one substrate molecule to an active site increases the likelihood of substrate binding to other subunits.

Question 19

A patient is exposed to a heavy metal such as mercury, which binds to the -SH groups of enzymes. What is the most likely effect on enzyme activity?

Accepted Answer

The enzyme will be irreversibly inhibited due to disruption of disulfide bonds.

Comprehensive Study Notes on Enzymes

Guida di studio - Domande di pratica

Study guide - Flashcard