Question

What are the different ways in which glucose is oxidized to provide energy in various organisms?

Answer 1

The reactions involved in respiration are catabolic reactions (aerobic and anaerobic respiration), which break large molecules such as glucose into smaller ones in most of the organisms, releasing energy because weak high-energy bonds, in particular in molecular oxygen, are replaced by stronger bonds in the products.

Complete answer:
(i) Aerobic respiration: Aerobic respiration requires oxygen (${O_2}$ ) in order to create the energy storing molecule, ATP. Although carbohydrates, fats, and proteins are consumed as reactants, aerobic respiration is the preferred method of pyruvate breakdown in glycolysis, and requires pyruvate to the mitochondria in order to be fully oxidized by the citric acid cycle. The products of this process are carbon dioxide and water, and the energy transferred is used to break bonds in ADP to add a third phosphate group to form ATP (adenosine triphosphate), by substrate-level phosphorylation, $NADH$ and $FAD{H_2}$ .
(ii) Anaerobic respiration: Anaerobic respiration is used by some microorganisms in which neither the oxygen (aerobic respiration) nor the pyruvate derivatives (fermentation) is the high-energy final electron acceptor. Rather, an inorganic acceptor such as sulfate or nitrate is used. The breakdown of glucose takes place in the absence of the oxygen.

Note:
Cellular respiration is a set of metabolic reactions and processes that take place inside the cells of the organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate (ATP), and then release waste products.