Question 1

Which of the following best describes an open thermodynamic system in the context of cellular biology?

Accepted Answer

A system that can exchange both matter and energy with its surroundings.

Question 2

According to the first law of thermodynamics, which statement is correct regarding energy in a closed system?

Accepted Answer

Energy can be exchanged with the surroundings in the form of work or heat.

Question 3

Which equation correctly represents the Gibbs free energy change for a process at constant temperature and pressure?

Accepted Answer

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

Question 4

A reaction has $$\Delta H = +5630 \ \mathrm{J/mol}$$ and $$\Delta S = +20.6 \ \mathrm{J/(K \cdot mol)} at$$ $$263 \ \mathrm{K}. $$What is $$\Delta G$$ and is the process favorable?

Accepted Answer

$$\Delta G = +212 \ \mathrm{J/mol}$$; unfavorable

Question 5

Which of the following statements about entropy ($$S) is $$correct?

Accepted Answer

Entropy measures the degree of randomness or disorder in a system.

Question 6

For a chemical reaction at equilibrium, which equation is true?

Accepted Answer

$$\Delta G = 0$$

Question 7

Given the reaction $$aA + bB \rightleftharpoons cC + dD$$, how is the equilibrium constant $$K$$ expressed?

Accepted Answer

$$K = \frac{[C]^c [D]^d}{[A]^a [B]^b}$$

Question 8

Which equation relates the standard free energy change to the equilibrium constant?

Accepted Answer

$$\Delta G^\circ = -RT \ln K$$

Question 9

In a living cell, the concentrations of reactants and products are maintained far from equilibrium. What is this condition called?

Accepted Answer

Homeostasis

Question 10

Which of the following is true about the coupling of unfavorable and favorable reactions in cells?

Accepted Answer

Coupling allows unfavorable reactions to proceed by using the energy from favorable reactions.

Question 11

What is the biochemical standard state for $$[H^+] at pH 7$$?

Accepted Answer

$$[H^+] = 10$$^{-7}$$ \ \mathrm{M}$$

Question 12

Which equation is used to calculate the actual free energy change ($$\Delta G) $$for a reaction under non-standard conditions?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln Q$$

Question 13

Which of the following phosphate compounds has the most negative $$\Delta G^\circ$$ for hydrolysis?

Accepted Answer

Phosphoenolpyruvate (PEP)

Question 14

Why does phosphoenolpyruvate (PEP) have a higher phosphoryl group transfer potential than ATP?

Accepted Answer

Because PEP hydrolysis is driven by resonance stabilization, charge repulsion, and tautomerization of products.

Question 15

If $$[A]_1 \u003c [A]_2$$ across a membrane, what is the sign of $$\Delta G$$ for the transfer of A from region 1 to region 2?

Accepted Answer

$$\Delta G is $$negative; transfer is favorable

Question 16

Which of the following best describes the role of ATP in cellular systems?

Accepted Answer

ATP acts as the common energy currency, driving many cellular processes.

Question 17

Which of the following is true regarding homeostasis and equilibrium in cells?

Accepted Answer

Homeostasis maintains steady-state concentrations far from equilibrium, requiring energy input.

Question 18

For the hydrolysis of ATP at pH 7.4 and 25°C, with $$[ATP] = 5 \ \mathrm{mM}$$, $$[ADP] = 0.1 \ \mathrm{mM}$$, and $$[$$HPO_4$$^{2-}] = 35 \ \mathrm{mM}$$, which statement is correct?

Accepted Answer

The actual $$\Delta G is $$much more negative than $$\Delta G^\circ.$$

Question 19

Which of the following is NOT a reason why PEP hydrolysis is highly exergonic?

Accepted Answer

Formation of a less stable product

The Energetics of Life: Thermodynamics and Free Energy in Biological Systems

Study Guide - Practice Questions

Study Guide - Flashcards