Question

Which of the following is not likely to favor an overall delta G value that is negative?

	A.	A molecule moving down its concentration gradient (i.e., high to low concentration)
	B.	ATP formation (i.e., ADP + Pi → ATP)
	C.	The complete oxidation of glucose to CO2 and water.
	D.	An electron acceptor with very positive reduction potential.
	E.	All are likely to favor an overall delta G value that is negative

Answer 1

Answer: Option B is correct
Explanation:
A negative ∆G represents a spontaneous exergonic process.

A moelcule can freely move along its concnetration gradient without input of energy = -∆G
The complete oxidative of glucose produces 686 kcal of energy = -∆G
An electron acceptor with positive ∆G can accept electrons more readily.

ATP hydrolysis is an exergonic reaction.
ATP ------> ADP + Pi
∆G = -7.3 kcal/mol

ATP synthesis exhibits a +∆G value.

Answer 2

The answer is D. An electron acceptor with a very positive reduction potential is not likely to favor an overall ΔG value that is negative.

In thermodynamics, the Gibbs free energy change (ΔG) is a measure of the spontaneity and directionality of a reaction. A negative ΔG value indicates that a reaction is thermodynamically favorable and tends to occur spontaneously.

Options A, B, and C all involve processes that are known to have a negative ΔG value:

A. A molecule moving down its concentration gradient: This is a passive transport process that occurs from an area of higher concentration to an area of lower concentration. It is driven by the concentration gradient and is energetically favorable.

B. ATP formation: The formation of ATP from ADP and Pi (inorganic phosphate) involves the coupling of an endergonic (non-spontaneous) reaction with an exergonic (spontaneous) reaction. This coupling results in a negative ΔG value, making the process energetically favorable.

C. The complete oxidation of glucose to CO2 and water: The oxidation of glucose is an exergonic process that releases energy. It involves a series of redox reactions that generate high-energy electron carriers, such as NADH and FADH2. The overall process has a negative ΔG value, indicating its thermodynamic favorability.

However, option D states an electron acceptor with a very positive reduction potential. A positive reduction potential indicates a tendency to gain electrons, which is associated with a spontaneous reduction reaction. Since the overall ΔG value is determined by the difference in reduction potentials of the reactants and products, a positive reduction potential for the electron acceptor would result in a positive ΔG value, indicating a non-spontaneous or unfavorable reaction.

Therefore, option D is not likely to favor an overall ΔG value that is negative