When does respiration occur in plants?

The compounds that are subjected to biological oxidation are called . . . . . . in which . . . . . . is the most common.

Respiration is an energy-releasing and enzymatically controlled catabolic process which involves a step-wise oxidative breakdown of organic substances inside living cells. In this statement about respiration,explain the meaning of $(a)$ Step-wise oxidative breakdown $(b)$ Organic substances (used as substrates).

The complete combustion of glucose in respiration is represented by:

Respiratory substrates are the organic substances which are ..... during respiration to liberate energy.

The main purpose of cellular respiration is to