Proteins (proteins), the essential structural element required for growth and metabolism in the human body and all living beings. Large proteins consist of smaller components - amino acids - and often have very complicated structure.
Proteins of various kinds play a critical role in the human body. Structural proteins of connective tissues contain collagen, a protein skin - keratin, muscle include actin and myosin, and cell is connected with tubulin.
Other proteins are enzymes, which accelerate chemical reactions within cells, hormones and antibodies are proteins that are involved in protecting the body against harmful influences and diseases. Blood proteins such as hemoglobin, albumin and others, responsible for what the blood coagulates, only when necessary, such as an injury.
AMINO ACIDS ARE THE BUILDING BLOCKS OF
Like all organic matter, protein molecules built from atoms of carbon, hydrogen and oxygen. In addition, proteins contain nitrogen and often sulfur.
The main structural unit of a protein molecule is an amino acid. There are about 20 types of amino acids, which can be connected, forming between them a huge number of different combinations. Some amino acids can be synthesized in the body, other come only from the external environment. To maintain health people should consume at least 30 grams of protein daily.
The basis of the amino acid molecules is a chain of carbon atoms. At the ends of the molecule are two different chemical groups: on the one hand the amino group and the carboxylic acid residue. The amino group of one amino acid can interact with the acid group of the contiguous amino acids with separation of water molecules - this process underlies the formation of long chains of amino acids.
The structure of the amino acids determines its solubility and amphoteric properties - the ability to act as acids and bases at the same time. This enables protein molecules to exist both in acid and in alkaline medium. Amino acids also have properties of buffer (control pH), which is crucial for homeostasis - to maintain a constant internal environment of the body.
Matrix for formations of a protein molecule is a DNA sequence. In the cell the synthesis of chains of amino acids occurs in the ribosomes (cellular component) using ribonucleic acid RNA.
THE PRIMARY STRUCTURE
The sequence of amino acids assembled in the ribosome, specifies the primary structure of the protein. The order of Assembly of amino acids, in turn, determines the DNA sequence. This primary structure is the skeleton of the protein molecule.
SECONDARY STRUCTURE
After a long polypeptide chain (amino acid sequence) is formed, it begins to organize in complex three-dimensional structure, only occasionally staying in the just chains of amino acids. The process of formation of secondary structure occurs due to the formation of hydrogen bonds, which, although quite weak, is strong enough to hold the special shape of the protein. The hydrogen atoms interact with certain atoms inside the formed chain of amino acids with the formation of two different shape models of the protein molecule.
The most common type of secondary structure is Ξ±-helix, twisted to the right. This structure is formed due to hydrogen bonding between every fourth amino acid. Another variety - Ξ²-folds - flat structure in which hydrogen bonds occur in two parallel polypeptide chains. Some protein molecules can be observed an alternation of both species of the secondary structure in different parts of the circuit.
Protein with very long polypeptide chain can further be minimized tertiary and Quaternary structure.
PROTEIN DENATURATION
Under normal conditions proteins are relatively stable. Their activity is determined by a three-dimensional structure and the links that hold the molecule intact. However, these interatomic bonds are sensitive to the effects of such factors as increased acidity and temperature. The process of loss protein its three-dimensional structure is called denaturation. In some cases, this process may be reversible. If the change of pH or temperature reach extreme values, the process is irreversible.
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