Final answer:
The energy required for anabolic reactions comes from ATP, which is generated during the catabolic metabolism of glucose and other molecules. Enzymes help facilitate these reactions, and excess heat is also a by-product.
Step-by-step explanation:
The energy required for anabolic reactions primarily comes from the metabolism of glucose and other similar molecules. These catabolic reactions break down glucose, which produces energy that is then stored in the form of adenosine triphosphate (ATP). ATP then acts as the primary energy currency for cells, providing the necessary energy to drive a myriad of endergonic, or energy-consuming, processes like anabolic reactions. These anabolic pathways are essential for the synthesis of complex molecules such as proteins from simpler ones like amino acids.
Enzymes play a crucial role in facilitating both anabolic and catabolic reactions by lowering the activation energy required for these processes to occur. The energy that is not used in the formation of ATP during catabolism is often released as heat, which can be absorbed by body tissues or used to maintain body temperature.