Explain why and how the malate-aspartate shuttle moves NADH reducing equivalents from the cytosol to the mitochondrial matrix.

There is no transporter for NADH in the inner mitochondrial membrane. However, NADH can be oxidized to NAD + by the cytoplasmic isozyme of malate dehydrogenase as oxaloac- etate is reduced to malate. The malate is transported across the inner membrane, and the mitochondrial isozyme of malate dehydro- genase oxidizes it to oxaloacetate as mito- chondrial NAD + is reduced to NADH. This NADH can be oxidized by Complex I of the electron transport chain, generating three ATP through the coupled processes of respiration and oxidative phosphorylation.