The sum total of all the chemical reactions occurring in the body is known as

The correct answer is metabolism.

To understand why this is the correct answer, let's break down the biochemical processes occurring within a living organism:
1. Metabolism: This is the sum total of all chemical reactions that occur within a living organism to maintain life. These reactions enable organisms to grow, reproduce, maintain their structures, and respond to their environments.
2. Catabolism: This is a specific division of metabolism. It refers to the set of metabolic pathways that break down larger, complex molecules into smaller, simpler units (for example, breaking down glucose into carbon dioxide and water to release energy).
3. Anabolism: This is the other primary division of metabolism. It refers to the biosynthetic pathways that construct larger, complex molecules from smaller, simpler units (for example, synthesizing proteins from amino acids, which requires an input of energy).
4. Homeostasis: This is the physiological state of steady internal physical and chemical conditions maintained by living systems, which is regulated and sustained by metabolic activities but is not itself the chemical reactions.

Since the question asks for the sum total of all chemical reactions (encompassing both breakdown/catabolic and synthesis/anabolic pathways), the correct term is metabolism.