Question 1

Which statement best describes the First Law of Thermodynamics as it applies to biological systems?

Accepted Answer

Energy cannot be created or destroyed, but it can be transferred and transformed from one form to another.

Question 2

A reaction in a cell has a negative change in Gibbs free energy ($$\Delta G \u003c 0). $$What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and can occur spontaneously, releasing energy.

Question 3

Which equation correctly represents the relationship between Gibbs free energy, enthalpy, and entropy?

Accepted Answer

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

Question 4

In the context of metabolic pathways, what is the primary role of enzymes?

Accepted Answer

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

Question 5

Which of the following best describes a coupled reaction in metabolism?

Accepted Answer

An exergonic reaction releases energy that is used to drive an endergonic reaction.

Question 6

During cellular respiration, glucose is oxidized and oxygen is reduced. Which of the following statements is correct regarding this redox reaction?

Accepted Answer

Glucose loses electrons and is oxidized, while oxygen gains electrons and is reduced.

Question 7

Which of the following is a real-life example of energy transformation in an ecosystem, as shown in the diagram with moose and trees?

Accepted Answer

Solar energy is converted to chemical energy in plants, which is then transferred to animals as mechanical energy, with heat lost at each step.

Question 8

Which of the following best explains why cells require a constant flow of energy to maintain order?

Accepted Answer

Cells are highly ordered, and maintaining this order requires energy input to counteract the tendency toward increased entropy.

Question 9

Which statement about enzyme specificity is correct?

Accepted Answer

Enzymes are specific for their substrate(s) and usually catalyze only one type of reaction.

Question 10

Which of the following factors does NOT affect the rate of an enzyme-catalyzed reaction?

Accepted Answer

Color of the substrate

Question 11

A competitive inhibitor affects an enzyme by:

Accepted Answer

Binding to the active site, preventing the substrate from binding.

Question 12

Which of the following is true about the effect of enzymes on the activation energy ($$E_a) $$and Gibbs free energy ($$\Delta G) of a $$reaction?

Accepted Answer

Enzymes lower the activation energy but do not change the net Gibbs free energy.

Question 13

Which of the following best describes the induced-fit model of enzyme action?

Accepted Answer

The enzyme changes shape to better fit the substrate, facilitating the transition state.

Question 14

Which of the following is a function of cofactors in enzyme activity?

Accepted Answer

Cofactors provide functional groups that amino acids lack, aiding in enzyme function.

Question 15

Which scenario best illustrates feedback inhibition in a metabolic pathway?

Accepted Answer

The end-product of the pathway binds to an allosteric site on the first enzyme, inhibiting its activity.

Question 16

Which of the following is true about the relationship between substrate concentration and the rate of an enzyme-catalyzed reaction?

Accepted Answer

The rate increases with substrate concentration but eventually reaches a maximum speed.

Question 17

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

Accepted Answer

Enzymes have optimal temperature and pH ranges, outside of which their activity decreases.

Question 18

Which of the following statements about metabolic redox reactions is correct?

Accepted Answer

Oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 19

Which of the following best explains why ATP hydrolysis is often coupled to endergonic reactions in cells?

Accepted Answer

ATP hydrolysis releases energy that can be used to drive endergonic reactions, making the overall process exergonic.

Metabolism I: Energy and Enzymes – Thermodynamics and Catalysis in Biological Systems

Study Guide - Practice Questions