Final answer:
Metabolism includes catabolism and anabolism, which are linked by ATP. Catabolic reactions require an input of ATP energy.
Step-by-step explanation:
Metabolism is the set of chemical reactions that occur in cells to maintain the cell's energy balance.
It includes two types of pathways: anabolic pathways, which require energy to synthesize larger molecules, and catabolic pathways, which generate energy by breaking down larger molecules.
Catabolism and anabolism are linked by ATP, which is used as a source of energy for anabolic reactions.
Anabolic reactions do not generate ATP; they require an input of ATP energy.
Therefore, option 2) 'Catabolism and anabolism are linked by ATP' is true of metabolism.