Question

A plant uses 54 ATP to build one glucose molecule, but only gets 36 ATP when it breaks the sugar down for energy. Why doesn't the plant run into an energy shortage? [4]

Answer 1

During biosynthesis i.e. anabolic processes, the plant uses huge amount of energy as ATP to synthesize biomolecules like sugar (glucose). But during breakdown i.e. catabolic processes, the net energy is released in the form of ATP. Thus, for synthesis of any compound, large amount of energy is needed but to break it down actually releases huge but lesser amount of energy. For example, to synthesize one molecule of glucose require 54 ATP, whereas only 36 ATP is released in the form of energy during its breakdown. Thus, there is a loss of energy during catabolic and anabolic processes. Therefore, when energy synthesis is lowered i.e. less ATP synthesis, it is difficult to synthesize biomolecules as well as to break it down and so a plant is unable to cope up with energy shortage due to reduction in catabolic and anabolic processes.