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?

Accepted Answer

The active site is a specific region formed by the three-dimensional folding of the enzyme, allowing it to bind to specific substrates.

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 used up.

Question 4

Which of the following is a correct statement about the effect of temperature on enzyme activity?

Accepted Answer

Enzyme activity increases with temperature up to an optimum, after which it decreases due to denaturation.

Question 5

A scientist is measuring 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 absorbance change in a colorimetric assay as starch is hydrolyzed by amylase.

Question 6

Which of the following best describes the difference between competitive and non-competitive enzyme inhibition?

Accepted Answer

Competitive inhibitors bind to the active site and can be outcompeted by high substrate concentration, while non-competitive inhibitors bind elsewhere and lower Vmax.

Question 7

Which equation correctly defines the Michaelis constant ($$K_m) $$for an enzyme-catalyzed reaction?

Accepted Answer

$$K_m is $$the substrate concentration at which the reaction rate is half of its maximum ($$\frac{1}{2}V_{max}).$$

Question 8

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 and substrate.

Question 9

Which of the following best explains why a drastic change in pH can denature an enzyme?

Accepted Answer

It disrupts the ionic and hydrogen bonds that maintain the enzyme's three-dimensional structure, altering the active site.

Question 10

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

Accepted Answer

$$K_m$$ remains unchanged, but $$V_{max}$$ decreases.

Question 11

Which of the following is an example of an enzyme requiring a cofactor for activity?

Accepted Answer

Carbonic anhydrase requiring $$Zn^{2+} as a $$cofactor for its catalytic activity.

Question 12

Which of the following best describes 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 13

Which of the following experimental results would indicate that an enzyme is being inhibited by a competitive inhibitor?

Accepted Answer

The Michaelis constant ($$K_m) $$increases, but the maximum velocity ($$V_{max}) $$can still be reached at high substrate concentrations.

Question 14

Which of the following best explains the concept of feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway acts as an allosteric inhibitor of an enzyme earlier in the pathway, thus regulating its own synthesis.

Question 15

Which of the following is a correct statement about the effect of substrate concentration on enzyme activity?

Accepted Answer

At low substrate concentrations, the rate of reaction increases linearly with substrate concentration, but plateaus at high concentrations when the enzyme is saturated.

Question 16

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

Accepted Answer

The active site is not perfectly complementary to the substrate until the substrate binds, causing the enzyme to change shape for a precise fit.

Question 17

Which of the following equations correctly represents the temperature coefficient ($$Q_{10}) $$for enzyme-catalyzed reactions?

Accepted Answer

$$Q_{10} = \frac{	ext{rate at } (x+10$$)^{\circ}$$C}{	ext{rate at } x$$^{\circ}$$C}$$

Question 18

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

Accepted Answer

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

Question 19

Which of the following is an example of cooperativity in enzyme regulation?

Accepted Answer

A substrate binding to one active site of a multi-subunit enzyme increases the affinity of other active sites for additional substrate molecules.

Comprehensive Study Notes on Enzymes

Guida di studio - Domande di pratica

Study guide - Flashcard