Biochemistry

Phosphoproteins. In these proteins, the phosphoric acid residue is linked via an ether bond to the hydroxyl group of serine or threonine. Phosphoproteins include many proteins that play an important role in the nutrition of a growing organism, in particular, milk protein - caseinogen, egg yolk - vitellin, fish eggs - ichthulin. A significant number of them are contained in the brain. Phosphoproteins perform many functions in living organisms. The addition of phosphorus to a protein (phosphorylation) changes the activity of the latter. Phosphorylation and dephosphorylation of proteins regulates their functioning in the cell. Glycoproteins. Prosthetic groups of glycoproteins are represented by carbohydrates and their derivatives. The carbohydrate component gives the protein molecule new properties, including high specificity. Unlike proteins, glycoproteins are characterized by thermal stability: they can withstand both low and high temperatures without changing their physicochemical properties. Glycoproteins are difficult to digest with proteolytic enzymes. Carbohydrate-containing proteins are found in all organisms. They play an important biological role: they perform functions such as transporting various substances, blood coagulation, maintaining immunity (protecting the body from infectious bacteria and viruses), etc. Mucins are the representatives of glycoproteins, which make saliva highly viscous, which facilitates the passage of food through the esophagus. Mucins protect the mucous membrane of the stomach and intestines from the effects of their own enzymes and poorly groundfood. Chromoproteins. These are complex proteins, in which the non-protein part is represented by various colored compounds, where their name comes (from the Greek. Chroma - paint). Among chromoproteins, hemoproteins (containing iron as a prosthetic group), porphyrins (containing magnesium), flavoproteins (containing isoalaxazine derivatives) are distinguished. Chromoproteins perform a number of unique functions, participating in the most important processes of life: photosynthesis, respiration, oxygen and carbon monoxide transport, redox reactions, light perception, etc. The prosthetic groups of chromoproteins include the porphyrin ring, flavin nucleotins, etc. Chromatoprotein belongs to. , hemoglobin, many enzymes - catalase, peroxidase, dehydrogenase, etc. Hemoglobin. Among the metal-containing chromoproteins, a blood coloring substance (pigment), hemoglobin, occupies a particularly important place. Hemoglobin of blood of vertebrates and humans is concentrated in red blood cells and appears in blood plasma only as a result of their destruction - hemolysis. Hemoglobin is readily decomposed by acetic acid and sodium chloride into two components: protein — globin and dye — heme. Globins of hemoglobins of blood of different animals are different in composition and location in their molecules of amino acids. As for the heme, in its 65