Cellular respiration harvests the most chemical energy from which of the following?
a) transferring electrons from organic molecules to pyruvate
b) substrate-level phosphorylation
c) generating carbon dioxide and oxygen in the electron transport chain
d) chemiosmotic phosphorylation
e) converting oxygen to atp

The answer is D-  Chemiosmotic phosphorylation

Explanation:

Cellular respiration is defined as a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into Adenosine triphosphate (ATP), and then release waste products. It is the process of breaking down sugar into a form that the cells can use as energy. Respiration is one of the key ways in which a cell releases chemical energy to fuel cellular activity. Usually, this process uses oxygen and is called aerobic respiration.

Chemiosmotic phosphorylation is the third pathway that produces ATP from inorganic phosphate and an ADP molecule. It is part of oxidative phosphorylation.

Most of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation and this works by the energy released in the consumption of pyruvate being used to create a chemiosmotic potential by pumping protons across a membrane.