What is the role of malate dehydrogenase in the citric acid cycle, and why is its reaction considered reversible under biological conditions?

• A. Malate dehydrogenase converts oxaloacetate to malate, and the reaction is irreversible due to a high positive delta G.
• B. Malate dehydrogenase converts malate to oxaloacetate, and the reaction is reversible due to a delta G close to zero under biological conditions.
• C. Malate dehydrogenase converts malate to fumarate, and the reaction is reversible due to a negative delta G.
• D. Malate dehydrogenase converts oxaloacetate to fumarate, and the reaction is irreversible due to a delta G close to zero.

Answer: (B)