Q: A reaction has $$\Delta H = -10$$ kcal/mol, $$\Delta S = +0.02$$ kcal/(mol·K), and $$T = 300 K. $$What is $$\Delta G$$ for this reaction?

$$\Delta G = -10 - (300 \times 0.02) = -16$$ kcal/mol

Question 1

Which of the following best describes the difference between kinetic and potential energy in biological systems?

Accepted Answer

Potential energy is stored energy, such as in chemical bonds, while kinetic energy is the energy of motion, such as muscle contraction.

Question 2

Which equation correctly relates Gibbs free energy ($$G$$), enthalpy ($$H$$), entropy ($$S$$), and absolute temperature ($$T) in a $$biological system?

Accepted Answer

$$G = H - TS$$

Question 3

A reaction has $$\Delta G = +5$$ kcal/mol. Which of the following statements is TRUE about this reaction?

Accepted Answer

The reaction is endergonic and requires an input of energy.

Question 4

Which of the following best explains why ATP is considered the 'energy currency' of the cell?

Accepted Answer

ATP contains high-energy phosphate bonds that, when hydrolyzed, release energy that can be used to drive endergonic reactions.

Question 5

According to the second law of thermodynamics, what happens to the entropy of a closed system over time?

Accepted Answer

Entropy increases, leading to more disorder.

Question 6

Which of the following statements about enzyme catalysis is correct?

Accepted Answer

Enzymes lower the activation energy but do not change the overall $$\Delta G of $$the reaction.

Question 7

A competitive inhibitor affects an enzyme-catalyzed reaction by:

Accepted Answer

Binding to the active site, preventing substrate binding.

Question 8

Which of the following is a correct statement about metabolic pathways?

Accepted Answer

Metabolic pathways are often regulated by feedback inhibition, where the end product inhibits an early step.

Question 9

If the equilibrium constant ($$K_{eq}) $$for a reaction is much greater than 1, what can be inferred about the reaction?

Accepted Answer

The reaction favors the formation of products and $$\Delta G is $$negative.

Question 10

Which of the following scenarios best illustrates energy coupling in a cell?

Accepted Answer

The hydrolysis of ATP is used to drive the phosphorylation of glucose, an endergonic reaction.

Question 11

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

Accepted Answer

The color of the enzyme

Question 12

A reaction has $$\Delta H = -10$$ kcal/mol, $$\Delta S = +0.02$$ kcal/(mol·K), and $$T = 300 K. $$What is $$\Delta G$$ for this reaction?

Accepted Answer

$$\Delta G = -10 - (300 	imes 0.02) = -16$$ kcal/mol

Question 13

Which of the following best describes feedback inhibition in a metabolic pathway?

Accepted Answer

The end product of the pathway binds to an allosteric site on the first enzyme, causing a conformational change that inhibits its activity.

Question 14

Which of the following statements about ATP hydrolysis is correct?

Accepted Answer

ATP hydrolysis releases energy that can be used to drive cellular work.

Question 15

Which of the following is a property of enzymes?

Accepted Answer

Enzymes are highly specific for their substrates.

Question 16

Which of the following is TRUE about noncompetitive enzyme inhibitors?

Accepted Answer

They bind to a site other than the active site, changing the enzyme's shape and function.

Question 17

Which of the following best explains why enzymes have an optimum temperature and pH?

Accepted Answer

Enzymes denature at temperatures and pH values far from their optimum, losing their functional shape.

Question 18

Which of the following is an example of an anabolic reaction?

Accepted Answer

The synthesis of proteins from amino acids.

Question 19

Which of the following statements about the coupling of exergonic and endergonic reactions is correct?

Accepted Answer

Coupling allows endergonic reactions to proceed by using the energy released from exergonic reactions.

Energy, Enzymes, and Metabolism: Study Notes

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