AP BIOLOGY

Detailed explanation-1: -Within the Krebs cycle, L-malate and NAD+ come together to form oxaloacetate, NADH, and H+. What type of chemical reaction is responsible for this step in the cycle? Explanation: In order for oxaloacetate to be formed, malate must lose electrons, which is the definition of an oxidation reaction.

Detailed explanation-2: -Steps in the Krebs Cycle Isocitrate is oxidized and decarboxylation occurs with a carbon dioxide molecule released. The coenzyme NAD+ is reduced to form another dinucleotide, NADH.

Detailed explanation-3: -Malate is converted to oxaloacetate in a reaction catalyzed by malate dehydrogenase. This reaction reduces an NAD+ molecule to NADH + H+.

Detailed explanation-4: -3) In the last reaction of the citric acid cycle, malate is dehydrogenated to regenerate the oxaloacetate necessary for the entry of acetyl coA into the cycle.

Detailed explanation-5: -In the cytosol, oxaloacetate is reduced to malate by electrons from NADH. Malate is then transported into the mitochondrial matrix via an oxaloacetate/malate antiporter. Inside the mitochondrion, malate is oxidized by NAD+ back to oxaloacetate forming NADH.