Question

The main purpose of cellular respiration is to
A. Convert potential energy to kinetic energy.
B. convert kinetic energy to potential energy.
C. Convert energy into cell chemicals.
D. Convert energy stored in the chemical bonds of glucose to the energy that a cell can use.

Answer 1

Cellular respiration is defined as the process where organisms use oxygen to break down the food molecules to get chemical energy for the normal function of the cell.

Complete answer:
Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy into adenosine triphosphate (ATP), from oxygen molecules and nutrients. The reactions involved in respiration are catabolic reactions, which break the large molecules into the smaller ones. Nutrients that are commonly used by animal and plant cells in respiration include sugar, amino acids and fatty acids, and most of the chemical energy is molecular oxygen. Fermentation is the process in which the glycolysis can take place without oxygen. The other three stages of cellular respiration: pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation which requires oxygen in order to occur. Only oxidative phosphorylation uses oxygen directly, but the other two stages can’t run without oxidative phosphorylation. Fermentation is less efficient at using the energy from glucose: only 2 ATP are produced per glucose, compared to the 38 ATP per glucose nominally produced by aerobic respiration. This is due to most of the energy of aerobic respiration derived from the molecule of oxygen with its relatively weak and high-energy double bond.
Hence, the correct answer is option D.

Note: The four main steps through which the cellular respiration occurs are glycolysis, pyruvate oxidation, citric acid cycle and oxidative phosphorylation. Most numbers of ATP’s are obtained in the TCA cycle of the cellular respiration.