CALCULATE ATP with the oxidation of one molecule of G3P

Question

Calculate the number of ATP generated by the oxidation of one molecule of G3P. Indicate where, what process, and by what type of phosphorylation these ATP are formed: Assume the malate/aspartate shuttle is being used.

b) State two reasons why this number in reality can be lower

Answer 1

The oxidation of one molecule of G3P (glyceraldehyde 3-phosphate) can generate two ATP molecules via substrate-level phosphorylation in the glycolysis pathway during the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate.

However, during the malate/aspartate shuttle, the electrons from NADH generated during glycolysis are transferred to the mitochondrial electron transport chain, resulting in oxidative phosphorylation, which generates a larger number of ATP molecules.

The exact number of ATP generated by the oxidation of one molecule of G3P through the malate/aspartate shuttle will vary depending on several factors, including the efficiency of the electron transport chain, the proton-motive force generated across the mitochondrial inner membrane, and the number of ATP synthase complexes in the mitochondria. However, on average, the oxidation of one molecule of G3P can generate around 30-32 ATP molecules via oxidative phosphorylation in the mitochondrial electron transport chain. However, under real physiological conditions

Two reasons why the actual number of ATP generated may be lower than the theoretical maximum include:

(1) the loss of energy due to leaky membranes or proton leak, which reduces the efficiency of the electron transport chain

(2) generation of reactive oxygen species (ROS) that can damage the electron transport chain components and decrease its efficiency.