Proteins serve as fundamental biomolecules within cellular life that act as structural components, biochemical catalysts (enzymes), defense agents (immunoglobulins), signaling molecules (hormones), and transport vehicles for specific ligands such as oxygen or ions. These macromolecules are polymeric chains composed of amino acid monomers, which constitute the primary endogenous source of nitrogen in biological systems due to their unique elemental composition containing carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus. Theoretical priority is assigned to proteins regarding structural integrity and catalytic regulation, whereas they function as a secondary metabolic energy reserve only after carbohydrates and lipids are depleted through catabolic deamination processes.
Proteins serve as fundamental biomolecules within cellular life that act as structural components, biochemical catalysts (enzymes), defense agents (immunoglobulins), signaling molecules (hormones), a…