Principles of Bioenergetics

Question 1

In terms of free energy, is having a negative change in enthalpy favorable or not?

Answer 1

A negative delta H is more favorable

Question 2

Is having a negative entropy favorable or not?

Answer 2

NO, having a positive delta S is more favorable

Question 3

If enthalpy is negative and entropy is positive, the reaction be spontaneous?

Answer 3

YES, it will have a negative delta G

Question 4

If enthalpy is positive and entropy is negative will the reaction be spontaneous?

Answer 4

NO. The reaction will have a positive delta G

Question 5

The biochemical reaction A ⇆ B has a large and positive change in free-energy (∆G&raquo_space; 1) under physiological conditions; which of the following is the best estimate for the equilibrium constant Keq?

Answer 5

Keq < 1: an unfavorable reaction, as a general rule, has an equilibrium constant between zero and one.

Question 6

The reaction A + B ⇆ C is EXOTHERMIC; if an equilibrium mixture of A, B, and C is heated slowly, what would happen to the concentrations of each species?

Answer 6

A+B increase, C decreases. Heat is a product of exothermic rxns, therefore, adding product shift the rxn towards reactants

Question 7

What is always true of spontaneous reactions?

Answer 7

A spontaneous reaction has a negative change in free energy aka decreases free energy

Question 8

ATP hydrolysis under standard biochemical conditions has ΔG«0, which implies which of the following about the reaction under these conditions?

Answer 8

It implies that the rxn is always spontaneous under regular conditions

Question 9

Which of the following best predicts the result of raising the pH of an equilibrium mixture for the reaction ATP + H2O ⇆ ADP + Pi + H+

Answer 9

ADP and H concentration rises to balance out the increasingly negative pH

Question 10

How does the free energy stored by ADP compare to the free energy stored by AMP under standard physiological conditions?

Answer 10

The free energy stored by ADP is positive and greater than the free energy stored by AMP, which is also positive

Question 11

Under which of the following conditions would one expect ATP hydrolysis to be non-spontaneous (aka have a positive Delta G)?

Answer 11

ATP concentrations very far below equilibrium concentration, and ADP concentrations very far above equilibrium concentration

Question 12

ATP hydrolysis is a spontaneous chemical reaction under standard physiological conditions: what is always true of spontaneous reactions?

Answer 12

That the products of the reaction have lower free energy than the reactants

Question 13

Glucose is oxidized to what molecule during aerobic cellular respiration?

Answer 13

Products of cell resp are H2O, CO2 and heat. Glucose oxidized to CO2

Question 14

Oxygen is reduced to what molecule during aerobic cellular respiration?

Answer 14

Products of cell resp are H2O, CO2 and heat. O2 is reduced to H2O

Question 15

Aerobic cellular respiration involves the flow of electrons from one chemical species to another: which of the following best describes this process?

Answer 15

Glucose is the ultimate source of electrons and O2 is ultimate acceptor. Flow of electrons goes Gluc to H2O

Question 16

Chemical reactions can be classified according to free energy changes. A chemical reaction has a ΔG of -686/kcal/mol. Is this an endergonic or exergonic reaction? How would the addition of catalyst change the ΔG this reaction?

Answer 16

Exergonic, catalysts wouldn’t affect the free energy at all

Question 17

What can be said about the levels of energy of products and reactants, and ΔG in cellular respiration.

Answer 17

The reactants glucose and oxygen have high levels of energy, and the products carbon dioxide and water have low levels of energy, ΔG is negative.

Question 18

The lightning bug is a beetle that can glow in the dark. Is bioluminescence an endergonic or exergonic reaction and what is the ΔG of bioluminescence?

Answer 18

Endergonic reaction with positive ΔG. Generating light is a very costly (endergonic) process

Question 19

ATP cycle refers to a set of reactions that promotes reversible changes of ATP into ADP via endergonic and exergonic reactions. According to Le Chatellier’s principle, what would you expect to occur if ADP levels increased?

Answer 19

Decreased levels of inorganic phosphate and increased levels of ATP and H2O

Question 20

The electron transport chain is an important chemical reaction of cellular respiration. What would occur if oxygen was not present in the electron transport chain (anaerobic conditions)?

Answer 20

Anaerobic respiration would still give off energy (exergonic) but it would do so at a lower magnitude than the aerobic respiration