What are proteins primarily used for in the body?

Proteins play a crucial role in the body primarily as the building blocks for cells and tissues. They are composed of amino acids, which are essential for the growth, repair, and maintenance of body structures. Proteins contribute to the formation of muscles, skin, enzymes, hormones, and various cell components. This fundamental role in structuring the body is what differentiates proteins from other macronutrients.

While proteins can be used for energy in certain situations, such as prolonged exercise or inadequate carbohydrate intake, this is not their primary function. Likewise, the transport of oxygen in the blood is mainly the role of hemoglobin, which is a specialized protein, but proteins in general are not primarily categorized for this function. Additionally, energy storage is predominantly handled by fats and carbohydrates, rather than proteins, which primarily serve structural and functional roles in the body's tissues. Thus, the assertion that proteins are primarily used for building and maintaining cells and tissues effectively captures their most vital role in human physiology.