Proteins are macromolecules composed of 20 standard amino acids, of which 9 are essential, and which are connected to each other by covalent peptide bonds. The sequence of amino acids in protein is formed by transcription of the coded genetic sequence from DNA and through translation via RNA. The polypeptide chain in its native form has a certain level of structure, which can be: primary, secondary, tertiary and quaternary structure. Protein functions are many and derive from the amino acid composition and the complexity of the structure. Proteins participate in storage (albumin), building (collagen), transport (hemoglobin), catalytic reactions (enzymes), muscle contraction function (myosin), immune function (antibodies), signaling function (insulin), regulatory function (PKA), and other specific functions of organism. In doing so, it is important to maintain a constant protein turnover rate in order to maintain homeostasis. Proteins evolve through changes in primary structures. By monitoring sequence homology within proteins and creating a phylogenetic tree, it is possible to monitor the evolutionary history of an organism. The conclusion is that proteins are essential macromolecules of the living world, not only for nutrition, growth and development, but also for the preservation of all accompanying processes in which they participate, since their degradation leads to an accelerated aging process and cell death.