Question 1

Which of the following best describes the role of enzymes in biological reactions?

Accepted Answer

Enzymes lower the activation energy, allowing reactions to proceed faster.

Question 2

A student is studying the effect of temperature on enzyme activity. At very high temperatures, the enzyme's activity drops sharply. What is the most likely explanation for this observation?

Accepted Answer

The enzyme denatures, losing its specific three-dimensional structure.

Question 3

Which equation correctly represents the change in free energy ($$\Delta G) $$for a chemical reaction?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 4

In a metabolic pathway, the product of one reaction serves as the substrate for the next. What is the advantage of organizing reactions in this way?

Accepted Answer

It enables regulation and efficient flow of metabolites through the pathway.

Question 5

Consider the following scenario: A competitive inhibitor is added to an enzyme-catalyzed reaction. What effect will this have on the reaction rate?

Accepted Answer

The reaction rate will decrease, but can be restored by increasing substrate concentration.

Question 6

Which of the following graphs best represents the effect of an enzyme on the activation energy of a reaction?

Accepted Answer

A graph showing a lower peak for the activation energy in the presence of an enzyme compared to without.

Question 7

A reaction has a negative $$\Delta G. $$What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and can occur spontaneously.

Question 8

Which statement best explains why enzymes are highly specific for their substrates?

Accepted Answer

Enzymes have active sites with unique shapes that fit only specific substrates.

Question 9

A noncompetitive inhibitor binds to an enzyme at a site other than the active site. What is the result of this binding?

Accepted Answer

The enzyme's shape is altered, reducing its activity regardless of substrate concentration.

Question 10

Which of the following is true about the relationship between entropy ($$S) $$and free energy ($$G) in $$biological systems?

Accepted Answer

As entropy increases, free energy decreases.

Question 11

A cell needs to synthesize a molecule that requires energy input. Which type of reaction is this?

Accepted Answer

Endergonic reaction

Question 12

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway inhibits an enzyme involved early in the pathway.

Question 13

If the temperature of a reaction is increased, which of the following is most likely to occur to the rate of an enzyme-catalyzed reaction before the enzyme denatures?

Accepted Answer

The rate increases up to an optimal temperature.

Question 14

Which of the following is NOT a way enzymes can lower activation energy?

Accepted Answer

Increasing the temperature of the reaction

Question 15

A scientist measures the rate of an enzyme-catalyzed reaction at different substrate concentrations. The rate increases rapidly at first, then levels off. What is the most likely explanation?

Accepted Answer

All enzyme active sites are occupied; the reaction has reached saturation.

Question 16

Which of the following is a real-world example of enzyme inhibition?

Accepted Answer

Penicillin inhibits bacterial enzymes involved in cell wall synthesis.

Question 17

Which of the following statements about the induced fit model of enzyme activity is correct?

Accepted Answer

The enzyme changes shape slightly to fit the substrate more closely.

Question 18

A reaction has $$\Delta H = -100 kJ/$$mol, $$T = 298 K$$, and $$\Delta S = 0.2 kJ/($$mol\cdot K). What is $$\Delta G$$ for the reaction?

Accepted Answer

$$\Delta G = -100 - (298 	imes 0.2) = -159.6 kJ/$$mol

Question 19

Which of the following is most likely to occur if an enzyme is exposed to a pH far outside its optimal range?

Accepted Answer

The enzyme will denature and lose its function.

Enzymes and Energy in Biological Systems: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards