Proteins (also known as polypeptides) are organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The division between "organic" and " made of amino acids Amino acids are molecules containing an amine group, a carboxylic acid group and a side chain. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent. In the alpha amino acids, the amino and carboxylate groups are attached to the arranged in a linear chain and folded into a globular form. The amino acids in a polymer A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties chain are joined together by the peptide bonds A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amine group of the other molecule, thereby releasing a molecule of water (H2O). This is a dehydration synthesis reaction (also known as a condensation reaction), and usually occurs between amino acids. The resulting CO-NH bond is between the carboxyl A carboxyl group is a set of four atoms bonded together and present in carboxylic acids, including amino acids. Usually abbreviated as either CO2H or COOH, this set of atoms constitutes a functional group. In every carboxyl group the carbon atom is attached to an oxygen atom by a double bond and to a hydroxyl group by a single bond. In this way a and amino Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines, trimethylamine, and aniline; see Category:Amines for groups of adjacent amino acid residues In chemistry, residue refers to the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. The sequence of amino acids in a protein is defined by the sequence A DNA sequence or genetic sequence is a succession of letters representing the primary structure of a real or hypothetical DNA molecule or strand, with the capacity to carry information as described by the central dogma of molecular biology of a gene A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cells and pass genetic traits to offspring. A modern working definition of a gene is "a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with, which is encoded in the genetic code The genetic code is the set of rules by which information encoded in genetic material is translated into proteins (amino acid sequences) by living cells. A more precise term for the concept might be "genetic cipher". The code defines a mapping between tri-nucleotide sequences, called codons, and amino acids. A triplet codon in a nucleic.^[1] In general, the genetic code specifies 20 standard amino acids; however, in certain organisms the genetic code can include selenocysteine Selenocysteine is an amino acid that is present in several enzymes — and in certain archaea The Archaea [ɑrˈkiə] are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon (sometimes spelled "archeon"). They have no cell nucleus or any other organelles within their cells. In the past they were viewed as an unusual group of bacteria and named archaebacteria but since the — pyrrolysine Pyrrolysine is a naturally occurring, genetically coded amino acid used by some methanogenic archaea in enzymes that are part of their methane-producing metabolism. Shortly after or even during synthesis, the residues in a protein are often chemically modified by post-translational modification Posttranslational modification is the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis for many proteins, which alters the physical and chemical properties, folding, stability, activity, and ultimately, the function of the proteins. Proteins can also work together to achieve a particular function, and they often associate to form stable complexes A multiprotein complex is a group of two or more proteins. Protein complexes are a form of quaternary structure. Proteins in a protein complex are linked by non-covalent protein-protein interactions, and different protein complexes have different degrees of stability over time. Protein complex formation often serves to activate or inhibit one or.^[2]

Like other biological macromolecules A macromolecule is a very large molecule most often created by some form of polymerization. In the context of biochemistry, the term may be applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles. The constituent molecules from which macromolecules are assembled are called such as polysaccharides Polysaccharides are polymeric carbohydrate structures, formed of repeating units joined together by glycosidic bonds. These structures are often linear, but may contain various degrees of branching. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules and nucleic acids A nucleic acid is a macromolecule composed of chains of monomeric nucleotides. In biochemistry these molecules carry genetic information or form structures within cells. The most common nucleic acids are deoxyribonucleic acid and ribonucleic acid (RNA). Nucleic acids are universal in living things, as they are found in all cells and viruses, proteins are essential parts of organisms and participate in virtually every process within cells The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular . Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion. Many proteins are enzymes Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their that catalyze Catalysis is the process in which the rate of a chemical reaction is either increased or decreased by means of a chemical substance known as a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. The catalyst may participate in multiple chemical transformations. Catalysts biochemical reactions and are vital to metabolism Metabolism is the set of chemical reactions that occur in living organisms to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories. Catabolism breaks down organic matter, for example to harvest energy in cellular. Proteins also have structural or mechanical functions, such as actin Actin is a globular, roughly 42-kDa protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans. Actin is the monomeric subunit of two types of filaments in cells: microfilaments, one of and myosin Myosins are a large family of motor proteins found in eukaryotic tissues. They are responsible for actin-based motility in muscle and the proteins in the cytoskeleton The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within the cytoplasm. The cytoskeleton is present in all cells; it was once thought this structure was unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton. It is a dynamic structure that maintains cell shape, protects the cell,, which form a system of scaffolding Scaffolding is a temporary frame used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes , although it can be made out of other materials. Bamboo is still used in some Asian countries like People's Republic of China that maintains cell shape. Other proteins are important in cell signaling Cell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue homeostasis. Errors in cellular information processing, immune responses Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses. They are typically made of basic structural units—each with two large heavy chains and two small light chains—to form, for example,, cell adhesion Cellular adhesion is the binding of a cell to a surface, extracellular matrix or another cell using cell adhesion molecules such as selectins, integrins, and cadherins, and the cell cycle The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication . In cells without a nucleus (prokaryotes), the cell cycle occurs via a process termed binary fission. In cells with a nucleus (eukaryotes), the cell cycle can be divided in two brief periods: interphase—during which. Proteins are also necessary in animals' diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism , and therefore must be supplied in the diet from food. Through the process of digestion Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be absorbed, for instance, by a blood stream. Digestion is a form of catabolism.that means break down of macro food molecules to smaller one, animals break down ingested protein into free amino acids that are then used in metabolism.

Proteins were first described by the Dutch chemist Gerhardus Johannes Mulder Gerardus Johannes Mulder was a Dutch organic chemist who described the chemical composition of proteins and after correspondence with Jöns Jakob Berzelius named them in his paper 'On the composition of some animal substances'. In the same publication he also proposed that animals draw most of their protein from plants and named by the Swedish chemist Jöns Jakob Berzelius Friherre Jöns Jacob Berzelius was a Swedish chemist. He worked out the modern technique of chemical formula notation, and is together with John Dalton, Antoine Lavoisier, and Robert Boyle considered a father of modern chemistry in 1838. The central role of proteins in living organisms was however not fully appreciated until 1926, when James B. Sumner James Batcheller Sumner was an American chemist. He shared the Nobel Prize in Chemistry in 1946 with John Howard Northrop and Wendell Meredith Stanley showed that the enzyme urease Urease is an enzyme that catalyzes the hydrolysis of urea into carbon dioxide and ammonia. The reaction occurs as follows: was a protein.^[3] The first protein to be sequenced was insulin Insulin is a hormone that has extensive effects on metabolism and other body functions, such as vascular compliance. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle, and stopping use of fat as an energy source. When insulin is absent , glucose is not taken, by Frederick Sanger Frederick Sanger, OM, CH, CBE, FRS is an English biochemist and twice a Nobel laureate in chemistry. He is the fourth (and only living) person to have been awarded two Nobel Prizes, who won the Nobel Prize for this achievement in 1958. The first protein structures to be solved were hemoglobin Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates and myoglobin Myoglobin is a single-chain globular protein of 153 amino acids, containing a heme prosthetic group in the center around which the remaining apoprotein folds. It has eight alpha helices and a hydrophobic core. It has a molecular weight of 16,700 daltons, and is the primary oxygen-carrying pigment of muscle tissues. Unlike the blood-borne, by Max Perutz Max Ferdinand Perutz, OM was an Austrian-British molecular biologist, who was awarded the Nobel Prize for Chemistry in 1962, shared with John Kendrew for their studies of the structures of hemoglobin and globular proteins. At Cambridge he supervised the PhD work of Francis Crick and James Watson in the Cavendish Laboratory as they determined the and Sir John Cowdery Kendrew Sir John Cowdery Kendrew, CBE, FRS was an English biochemist and crystallographer who shared the 1962 Nobel Prize in Chemistry with Max Perutz; their group in the Cavendish Laboratory investigated the structure of heme-containing proteins, respectively, in 1958.^[4][5] The three-dimensional structures of both proteins were first determined by x-ray diffraction analysis; Perutz and Kendrew shared the 1962 Nobel Prize in Chemistry The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature, peace, and physiology or medicine. This award is for these discoveries. Proteins may be purified Protein purification is a series of processes intended to isolate a single type of protein from a complex mixture. Protein purification is vital for the characterisation of the function, structure and interactions of the protein of interest. The starting material is usually a biological tissue or a microbial culture. The various steps in the from other cellular components using a variety of techniques such as ultracentrifugation, precipitation, electrophoresis Electrophoresis is the best-known electrokinetic phenomenon. It was discovered by Reuss in 1807. He observed that clay particles dispersed in water migrate under influence of an applied electric field. There are detailed descriptions of electrophoresis in many books on colloid and interface science. There is an IUPAC Technical Report prepared by a, and chromatography Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures. It involves passing a mixture dissolved in a "mobile phase" through a stationary phase, which separates the analyte to be measured from other molecules in the mixture based on differential partitioning between the mobile and; the advent of genetic engineering Genetic engineering, recombinant DNA technology, genetic modification/manipulation and gene splicing are terms that apply to the direct manipulation of an organism's genes. Genetic engineering is different from traditional breeding, where the organism's genes are manipulated indirectly. Genetic engineering uses the techniques of molecular cloning has made possible a number of methods to facilitate purification. Methods commonly used to study protein structure and function include immunohistochemistry Immunohistochemistry or IHC refers to the process of localizing antigens in cells of a tissue section exploiting the principle of antibodies binding specifically to antigens in biological tissues. It takes its name from the roots "immuno," in reference to antibodies used in the procedure, and "histo," meaning tissue (compare to, site-directed mutagenesis Site-directed mutagenesis is a molecular biology technique in which a mutation is created at a defined site in a DNA molecule, usually a circular molecule known as a plasmid. In general, site-directed mutagenesis requires that the wild-type gene sequence be known, and mass spectrometry Mass spectrometry is an analytical technique for the determination of the elemental composition of a sample or molecule. It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds. The MS principle consists of ionizing chemical compounds to generate charged molecules or molecule fragments.

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