Question

1. what is metabolism? the rate at which food is digested. the process of maintaining body temperature. the sum of all chemical reactions within an organism. the breakdown of nutrients into energy.

Explanation:

Metabolism refers to the sum of all chemical reactions in an organism, encompassing both anabolism (building - up processes) and catabolism (breaking - down processes). The other options are partial aspects of metabolic processes.

Answer:

The sum of all chemical reactions within an organism.