What is a primary role of protein in the body?

The primary role of protein in the body is to build and repair body cells. Proteins are essential macromolecules composed of amino acids, which play a critical role in the structure and function of cells, tissues, and organs. They contribute to muscle repair after exercise, support the growth of new cells, and are vital for the maintenance of body tissues. Proteins also serve as enzymes and hormones, facilitating various biochemical reactions and regulatory processes.

The other options reflect functions of different biological molecules or processes. For example, hydration is primarily managed by water and electrolytes, while neurotransmitters are synthesized from various nutrients including amino acids but also require co-factors like vitamins. Similarly, while the body does regulate temperature, this function is mainly controlled by mechanisms such as sweating and blood flow rather than by protein directly.