Question 1

Which of the following best describes the concept of enthalpy ($$H) in $$biological systems?

Accepted Answer

The heat exchanged between a system and its surroundings at constant pressure.

Question 2

A reaction has $$\Delta H \u003e 0$$ and $$\Delta S \u003e 0. $$Under what temperature conditions will this reaction be spontaneous?

Accepted Answer

At high temperatures only.

Question 3

Which statement about entropy ($$S) is $$correct?

Accepted Answer

Entropy is a measure of disorder or randomness in a system.

Question 4

Consider the hydrolysis of ATP under cellular conditions: ATP + H$$_2O$$ $$\rightarrow$$ ADP + HPO$$_4$$^{2-}$$ + H$$^+$$. If $$[ATP] = 5$$ mM, $$[ADP] = 0.1$$ mM, $$[$$HPO_4$$^{2-}] = 35$$ mM, and pH = 7.4$, which equation would you use to calculate $$\Delta G$$?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln \left( \frac{[ADP][$$HPO_4$$^{2-}][H^+]}{[ATP][H_2O]} \right)$$

Question 5

Which of the following is true about reversible and irreversible processes?

Accepted Answer

Reversible processes have equal forward and reverse rates at equilibrium.

Question 6

A cell couples the hydrolysis of ATP ($$\Delta G^\circ = -30 kJ/$$mol) to an unfavorable reaction ($$\Delta G^\circ = +10 kJ/$$mol). What is the overall $$\Delta G^\circ$$ for the coupled process?

Accepted Answer

$$-20 kJ/$$mol

Question 7

Which of the following best explains why the breakdown of glucose to CO$$_2$$ and H$$_2O $$yields the same energy whether measured by combustion or biochemically?

Accepted Answer

Because enthalpy is a state function and depends only on initial and final states.

Question 8

Which of the following is NOT a characteristic of an open thermodynamic system?

Accepted Answer

It cannot exchange energy or matter with its surroundings.

Question 9

At equilibrium, which of the following is true for a chemical reaction?

Accepted Answer

$$\Delta G = 0$$

Question 10

Which equation correctly relates the standard free energy change ($$\Delta G^\circ) to $$the equilibrium constant ($$K$$)?

Accepted Answer

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

Question 11

Which of the following statements about the second law of thermodynamics is correct?

Accepted Answer

The entropy of an isolated system will tend to increase to a maximum value.

Question 12

Which of the following reactions is exergonic?

Accepted Answer

$$\Delta G \u003c 0$$

Question 13

A reaction has $$\Delta H \u003c 0$$ and $$\Delta S \u003c 0. At $$what temperature will this reaction be spontaneous?

Accepted Answer

At low temperatures only.

Question 14

Which of the following best describes the role of coupled reactions in cellular metabolism?

Accepted Answer

They allow endergonic reactions to proceed by pairing them with exergonic reactions.

Question 15

Which of the following is true about the biochemical standard state ($$\Delta G^\circ'$$)?

Accepted Answer

It accounts for physiological concentrations of H$$^+$$ and H$$_2O.$$

Question 16

Which of the following is a correct application of the first law of thermodynamics in a closed system?

Accepted Answer

Energy can be exchanged with the surroundings as work or heat.

Question 17

Which of the following scenarios best illustrates an irreversible process?

Accepted Answer

Burning paper to ash.

Question 18

Which of the following is true for living systems regarding thermodynamic equilibrium?

Accepted Answer

Living systems operate far from equilibrium under typical conditions.

Question 19

Which of the following equations is used to determine the spontaneity of a reaction?

Accepted Answer

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

Question 20

If a reaction is endergonic ($$\Delta G \u003e 0$$), which of the following statements is true?

Accepted Answer

The reverse reaction is spontaneous.

Chapter 3: The Energetics of Life – Thermodynamics in Biochemistry

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