Question

The number of ATP molecules formed during aerobic respiration in the breakdown of one glucose molecules via the malate-aspartate shuttle is
(a) 38
(b) 18
(c) 28
(d) 4

Answer 1

Aerobic respiration takes place in the presence of oxygen and is the important chemical process that is carried out by all living organisms including plants, animals, and humans for the release of energy that is required for life processes.

Complete answer:
The number of ATP molecules formed during aerobic respiration in the breakdown of one glucose molecule via the malate-aspartate shuttle is 38. It is a biochemical system that is used for translocating electrons across the semipermeable inner membrane of the mitochondria that are produced during the process of glycolysis for the oxidative phosphorylation in the eukaryotic organisms. The electrons enter through the reduction equivalent in the electron transport chain of the mitochondria to generate ATP molecules. The mitochondrial inner membrane is the impermissible membrane to the NADH which is the primary reducing equivalent to the electron transport chain and is required by the system. The malate carries the reducing equivalents across the membrane to avoid the primary reduction. It is capable of maximizing the number of ATPs produced in the process of glycolysis as the malate-aspartate shuttle regenerates NADH inside the mitochondrial matrix.

Additional information:
The process involves the primary enzyme which is malate dehydrogenase which is present in two forms in the shuttle system as mitochondrial malate and dehydrogenase and cytosolic malate dehydrogenase. They are differentiated by their location and structure and catalyze their reactions in opposite directions during the process. The activities done by the malate aspartate shuttle are modulated by arginine methylation of the malate dehydrogenase which inhibits MDH1 by disrupting its dimerization that represses the malate-aspartate shuttle and inhibits the pancreatic cancer cells in mitochondrial respiration.
So, the correct answer is option (a) '38'.

Note: The malate aspartate shuttle constitutes protein parts that include malate dehydrogenase, aspartate aminotransferase, malate alpha-ketoglutarate antiporter, and glutamate aspartate antiporter. They are present in the mitochondrial matrix and intermembrane space.