What is the primary function of proteins in the body?

The primary function of proteins in the body is to build up tissue. Proteins play a crucial role in the structure and function of cells, as they are the building blocks of the body's tissues. They are essential for growth, repair, and maintenance of not just muscle tissue but also other types of cells and tissues such as skin, organs, and blood. Each protein is made up of amino acids, which are linked together in specific sequences to form various proteins needed by the body for numerous functions, including enzymatic reactions and signaling.

While proteins can provide energy, this is not their primary role. The body primarily uses carbohydrates and fats for that purpose. The regulation of body temperature is managed by other mechanisms in the body, such as metabolism and the actions of the nervous system. Lastly, while certain proteins (like hemoglobin) do play a role in delivering oxygen to cells, this is a specific function of some proteins rather than their overall primary function. Thus, building and maintaining tissue is the fundamental role of proteins in the body.