Protein Stein Structure

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This writing presents the structure of proteins, their importance for life and processes under which they are made. It will also describe two groups of proteins and give some examples.

Proteins (also called polypeptides, peptides or amino acids) are large polymers and main components of cells. They are produced by condensation reaction from amino acid monomers, therefore proteins are called condensation polymers. Each protein is formed by a unique sequence of 20 naturally occurring amino acids. However, not all the amino acids need to be find in one protein. Some can be found many times and some are not used at all. Among other things, proteins provide building material, create moving apparatus, have transport role in organisms and play
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These two groups react in condensation reaction (polymerisation) to give amide, with peptide bond between carbon atom and nitrogen atom, and water. A final protein is made by a chain of amino acids with N-terminus, contains -NH2 group, on one side and C- terminus, with -COOH group, on the other side of the chain. Between these two terminuses lie groups of hydrocarbons left after reactions among the amino acids. These are the amino acid residues and their sequence determined the primary structure of a protein.

Proteins are condensed of hundreds or thousands of amino acid monomers. With the 20 naturally occurred amino acids the number of different sequences of amino acid residues in a protein is vast. Each of the amino acid can take different position in the protein chain and can undergo reaction with the same amino acid. If one protein can contains many of the same amino acids in different positions there must be almost limitless number of proteins.

The shape of protein depends on the three dimensional folding pattern called higher-order structure. It originates in the primary structure and is hold together by weak non-covalent interactions between amino acid residues. These could be hydrophobic interactions and hydrogen or ionic bonds. The proteins ' shape determine its biological
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Globular proteins have more specific roles and rely on 'pockets ' in their surfaces called binding sites (or active sites in the enzymes case). The shape of these 'pockets ' are very specific and define the biological function of the protein. First example can be enzymes, which names usually finished on -ase (e.g. cellulase). They play vital role in metabolism and function as biological catalysts by lowering the energy barrier of reactions and can be mostly find inside of cells. As every catalyst they undergo reactions without change and can be used over and over again. Molecules called substrates bind by weak chemical interactions into the active sites of enzymes. This is known as enzyme- substrate complex. During a reaction the bonds in the substrate are distorted and product(s) are released. A further example of globular proteins are coenzymes, small organic molecules, which collaborate with enzymes. Coenzymes are used during a process called dehydrogenation where (usually two) hydrogen atoms are removed from the substrate. The process starts when coenzyme (e.g. NAD) binds to the enzyme to another binding side beside the active side for the substrate. During the reaction the coenzyme is reduced and transport the two hydrogen atoms from substrate to another reaction. The coenzyme then returns back to the enzyme. For this reason, coenzymes are often called transfer

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