$$\Delta G = \Delta G^\circ + RT \ln \frac{[\text{products}]}{[\text{reactants}]}$$

Question 1

Which statement best explains how the second law of thermodynamics applies to living cells?

Accepted Answer

Cells decrease entropy within themselves, but increase entropy in their surroundings by releasing heat.

Question 2

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

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln \frac{[	ext{products}]}{[	ext{reactants}]}$$

Question 3

A reaction has $$\Delta G^\circ = -1.8$$ kcal/mol. If the concentration of product is much higher than reactant, what will happen to $$\Delta G$$?

Accepted Answer

$$\Delta G$$ will become less negative and may even become positive, making the reaction unfavorable.

Question 4

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

Accepted Answer

Enzymes lower the activation energy, increasing the rate of reaction without changing $$\Delta G.$$

Question 5

Which statement about ATP and NADPH is correct?

Accepted Answer

ATP carries energy in the form of phosphate groups, while NADPH carries energy as high-energy electrons.

Question 6

Which of the following reactions is energetically favorable and can occur spontaneously?

Accepted Answer

Glucose + 6O$$_2$$ $$\rightarrow 6CO$_2 + 6H$_2O $$with $$\Delta G^\circ = -686$$ kcal/mol

Question 7

What is the effect of a competitive inhibitor on enzyme kinetics?

Accepted Answer

It increases the apparent $$K_m$$ without affecting $$V_{max}.$$

Question 8

Which equation relates the equilibrium constant ($$K_{eq}) to $$the standard free energy change ($$\Delta G^\circ$$)?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 9

Which activated carrier is primarily used to transfer high-energy electrons in biosynthetic (anabolic) reactions?

Accepted Answer

NADPH

Question 10

A condensation reaction forming a peptide bond is energetically unfavorable. How do cells drive this reaction?

Accepted Answer

By coupling it to ATP hydrolysis, which provides a negative $$\Delta G.$$

Question 11

Which of the following best describes the relationship between oxidation and reduction in biological systems?

Accepted Answer

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

Question 12

Which process is responsible for the conversion of sunlight into chemical bond energy in cells?

Accepted Answer

Photosynthesis

Question 13

If a reaction has $$\Delta G \u003e 0$$, what must occur for it to proceed in a cell?

Accepted Answer

It must be coupled to an energetically favorable reaction with $$\Delta G \u003c 0.$$

Question 14

Which statement about enzyme-catalyzed reactions is correct?

Accepted Answer

Enzymes lower the activation energy for both forward and reverse reactions by the same amount.

Question 15

Which of the following is true about $$K_m in $$enzyme kinetics?

Accepted Answer

$$K_m is $$the substrate concentration at which the reaction rate is half of $$V_{max}.$$

Question 16

Which of the following best describes the role of NAD$$^+ in $$catabolic reactions?

Accepted Answer

NAD$$^+$$ acts as an oxidizing agent, accepting electrons during catabolic reactions.

Question 17

Which of the following is a real-world example of a coupled reaction in cellular metabolism?

Accepted Answer

The synthesis of sucrose from glucose and fructose, driven by ATP hydrolysis.

Question 18

Which statement about the equilibrium point of a reaction is correct?

Accepted Answer

At equilibrium, the forward and reverse reaction rates are equal, but reactant and product concentrations may differ.

Question 19

Which of the following is NOT a group carried by an activated carrier molecule?

Accepted Answer

Hydroxyl group

Energy, Catalysis, and Biosynthesis: Microbial Metabolism and Enzyme Function

Study Guide - Practice Questions