Respiration is part of the metabolic process where the nutrients are converted into useful energy for regular cell activities. It is in two mode depending on presence or absence of oxygen. Aerobic respiration is the one where oxygen is involved and anaerobic respiration is the process where oxygen is absent. One of the factor regulating rate of respiration is the temperature and the ${\mathrm{Q}}_{10}$ temperature co-efficient for respiration in the range of $0–{25}^{\mathrm{o}}\mathrm{C}$ is 2, which means rate of respiration doubles for every ${10}^{\mathrm{o}}\mathrm{C}$ rise in temperature. The rate of change of a biological or chemical system as a consequence of increasing the temperature by ${10}^{\mathrm{o}}\mathrm{C}$ is referred to as ${\mathrm{Q}}_{10}$ temperature co-efficient which is a value without a unit.

Cytochromes are group of heme proteins and pigment molecules that undergo redox reactions aiding in ATP production in ETC. These are macromolecules made of porphyrin compounds having iron-component.

Respiratory rate of wounded or injured plant parts generally increases as it requires energy for healing and repair.