#Protein....!?

Proteins are biological macromolecules found in all living cells. They are formed of one or more polypeptide chains. Each of these chains consists of the sequence of amino acid residues linked together by peptide bonds.

Proteins provide a multitude of functions within the living cell and in tissues. These are enzymatic proteins (enzymes) that catalyze the chemical reactions of synthesis and degradation necessary for the metabolism of the cell. Other proteins provide a structural role within the cytoskeleton or tissues (actin, collagen), some are molecular motors that allow mobility (myosin), others are involved in the conditioning of DNA (histones), the regulation of gene expression (transcription factors) or the transmission of cellular signals (membrane receptors).

The protein chains are synthesized in the cell by the ribosomes, from the information coded in the genes, which determine the order in which the 22 amino acids, called proteinigenic, which are incorporated directly during the biosynthesis of proteins. The sequence of amino acids is called the polypeptide sequence. Post-translational modifications may occur after the protein has been synthesized, which may have the effect of modifying its physical or chemical properties. It is also common for non-protein molecules, called prosthetic groups, to bind stably to proteins and play a decisive role in their biological functions: this is the case, for example, with heme in hemoglobin, without which this protein could not carry oxygen in the blood.

Proteins adopt a three-dimensional structure that allows them to perform their biological function. This particular structure is determined primarily by their amino acid sequence whose various physicochemical properties lead the protein chain to adopt a stable folding.

In the laboratory, they can be separated from other cellular constituents using various techniques such as ultracentrifugation, precipitation, electrophoresis and chromatography. Genetic engineering has introduced a large number of methods to facilitate the purification of proteins. Their structure can be studied by immunohistochemistry, site-directed mutagenesis, X-ray crystallography, nuclear magnetic resonance and mass spectrometry.

Proteins are an important component of animal nutrition, they are degraded in the digestive tract and the released amino acids are then reused by the body.
Biochemistry
The proteins are formed of one or more polypeptide chains, which are linear biopolymers, which can be very long, composed of about twenty different L-α-amino acids. Protein is generally referred to as more than 50 residues in the molecule1, and peptide up to a few tens of residues.