Fermentation is the incomplete breakdown of glucose (anaerobic respiration) that occurs without oxygen. In alcoholic fermentation, pyruvic acid is converted into ethanol and carbon dioxide (for example by yeast), which is used in brewing and baking. In lactic acid fermentation, pyruvic acid is converted into lactic acid (for example in our muscles during vigorous exercise and by Lactobacillus in curd formation). Both release only a small amount of energy.

The respiratory quotient (RQ) is the ratio of the volume of carbon dioxide released to the volume of oxygen consumed during respiration. RQ = volume of CO2 evolved / volume of O2 consumed. For carbohydrates, which are completely oxidised, the value of RQ is 1. For fats the RQ is less than 1 (about 0.7) and for organic acids it is greater than 1.

RQ = CO2 evolved / O2 consumed

Growth is an irreversible and permanent increase in the size, mass or number of cells of an organism or its parts. In plants, growth has three phases along the growing region: (1) the phase of meristematic (cell division) activity at the tips of roots and shoots; (2) the phase of elongation, in which cells just behind the meristem enlarge; and (3) the phase of maturation, in which the enlarged cells differentiate and attain their final form and function.