1.1. Biological Functions of Proteins
The structure and function of cells determine a large number of different molecules: proteins, nucleic acids, carbohydrates. Proteins play a special role in the life of the cell. First of all, the specific features of the structure and functioning of the cell are determined by a set of proteins synthesized in it. More than half of its dry substance is attracted to the share of proteins inside the cell. In the human body there are more than 50,000 individual proteins. A set of proteins in the body determines individual specificity, the set of proteins in different cell types determines their morphological and functional features.
Protein functions
► Structural function. Proteins are directly involved in the construction of the cell membranes and cytoskeleton (integral, semi-integral and surface proteins). The substance of connective tissue and the extracellular matrix form proteins collagen, elastin, keratin, proteoglycans.
► Enzymatic function. All enzymes are proteins. Enzymes catalyze the transformations of various molecules in the cells of the body. Enzymes constitute more than 50% of all proteins.
► Receptor function. This function is the selective binding of hormones, biologically active substances and mediators on the surface of membranes or inside the cells.
► Transport function. Only proteins transport some substances in the blood. For example, lipoproteins (lipid transfer), hemoglobin (oxygen transport), transferrin (iron transport). Proteins transport cations of calcium, magnesium, sodium and other ions into the blood.