Question 1

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

Accepted Answer

Energy can be transformed from one type to another, but cannot be created or destroyed.

Question 2

A chemical reaction has a $$\Delta G of$$ $$-4.3$$ kcal/mol. Which of the following is true about this reaction?

Accepted Answer

It is exergonic and spontaneous.

Question 3

Which of the following best explains why cells must continually acquire energy from their environment?

Accepted Answer

To maintain order and counteract the natural tendency toward disorder.

Question 4

Given the reaction $$Y \rightarrow X$$ with $$[X]_{eq} = 1.8 M $$and $$[Y]_{eq} = 0.2 M$$, what is the equilibrium constant $$K_{eq}$$?

Accepted Answer

$$K_{eq} = 9$$

Question 5

Which of the following is true about the relationship between $$K_{eq}$$ and $$\Delta G^\circ$$ for a reaction?

Accepted Answer

If $$K_{eq} \u003e 1$$, $$\Delta G^\circ is $$negative and the reaction is spontaneous.

Question 6

Which of the following best describes energetic coupling in cells?

Accepted Answer

It connects exergonic and endergonic reactions so that the energy released from one can drive the other.

Question 7

ATP hydrolysis is often coupled to endergonic reactions in cells. What is the main reason for this?

Accepted Answer

ATP hydrolysis is exergonic and releases energy that can be used to drive endergonic reactions.

Question 8

Which of the following is an example of a redox reaction in biological systems?

Accepted Answer

The transfer of electrons from NADH to pyruvate, forming lactate and NAD$$^+.$$

Question 9

In the reaction: Lactate + NAD$$^+$$ $$\rightarrow$$ Pyruvate + NADH + H$$^+$$, which molecule is oxidized?

Accepted Answer

Lactate

Question 10

Which of the following statements about entropy is correct?

Accepted Answer

Entropy is a measure of disorder; spontaneous processes increase the entropy of the universe.

Question 11

A reaction has $$\Delta G = +2.8$$ kcal/mol. Which of the following is true?

Accepted Answer

The reaction is endergonic and will not proceed spontaneously.

Question 12

Which of the following best describes what happens to the potential energy of electrons as they move from nonpolar to polar bonds?

Accepted Answer

Potential energy decreases as electrons move to polar bonds.

Question 13

Which of the following is a correct statement about the hydrolysis of ATP?

Accepted Answer

It is an exergonic reaction that releases energy.

Question 14

If a cell needs to drive an energetically unfavorable reaction, which of the following strategies would it most likely use?

Accepted Answer

Couple the reaction to the hydrolysis of ATP.

Question 15

Which of the following best describes the role of kinases in cellular metabolism?

Accepted Answer

Kinases catalyze the addition of phosphate groups to substrates, often using ATP.

Question 16

Which of the following is true about oxidation and reduction in biological systems?

Accepted Answer

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

Question 17

A cell is synthesizing a macromolecule by joining monomers together. Which process is most likely coupled to this reaction?

Accepted Answer

Hydrolysis of nucleoside triphosphates (NTPs)

Question 18

Which of the following best explains why the breakdown of glucose is exergonic?

Accepted Answer

The products (CO$$_2$$ and H$$_2O) $$have lower potential energy than glucose and O$$_2.$$

Question 19

Which of the following is a correct interpretation of the Second Law of Thermodynamics in the context of living cells?

Accepted Answer

Cells must increase the entropy of the universe even as they maintain internal order.

Energy and Enzymes: Thermodynamics in Biological Systems

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