RNA 5' Cap:

The 5' cap is a specially altered nucleotide end to the 5' end of precursor messenger RNA and some other primary RNA transcripts as found in eukaryotes and, as a special exception, caliciviruses such as norovirus. The process of 5' capping is vital to creating mature messenger RNA which is then able to undergo translation. Capping ensures the messenger RNA's stability while it undergoes translation in the process of protein synthesis, and is a highly regulated process which occurs in the cell nucleus. 5' cap structure Ribose structure showing the positions of the 2', 3' and 5' carbonsThe 5' cap is found on the 5' end of an mRNA molecule and consists of a guanine nucleotide connected to the mRNA via an unusual 5' to 5' triphosphate linkage. This guanosine is methylated on the 7 position directly after capping in vitro by a methyl transferase. It is referred to as a 7-methylguanosine cap, abbreviated m7G/ Further modifications include the possible methylation of the 2' hydroxy-groups of the first 3 ribose sugars of the 5' end of the mRNA. The methylation of both 2' hydroxy-groups is shown on the diagram

Functionally the 5' cap looks like the 3' end of an RNA molecule (the 5' carbon of the cap ribose is bonded, and the 3' unbonded). This provides significant resistance to 5' exonucleases… Capping process The starting point is the unaltered 5' end of an RNA molecule. This features a final nucleotide followed by three phosphate groups attached to the 5' carbon. 1. One of the terminal phosphate groups is removed (by a phosphatase), leaving two terminal phosphates. 2. GTP is added to the terminal phosphates (by a guanylyl transferase), losing two phosphate groups (from the GTP) in the process. This results in the 5' to 5' triphosphate linkage. 3. The 7-Nitrogen of guanine is methylated (by a methyl transferase). 4. Other methyltransferases are optionally used to carry out methylation of 5' proximal nucleotides.

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Biochemistry-protiens:

Proteins are linear polymers built from 20 different L-α-amino acids. All amino acids possess common structural features, including an α carbon to which an amino group, a carboxyl group, and a variable side chain are bonded. Only proline differs from this basic structure as it contains an unusual ring to the N-end amine group, which forces the CO–NH amide moiety into a fixed conformation.The side chains of the standard amino acids, detailed in the list of standard amino acids, have different chemical properties that produce three-dimensional protein structure and are therefore critical to protein function. The amino acids in a polypeptide chain are linked by peptide bonds formed in a dehydration reaction. Once linked in the protein chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen, and oxygen atoms are known as the main chain or protein backbone. The peptide bond has two resonance forms that contribute some double-bond character and inhibit rotation around its axis, so that the alpha carbons are roughly coplanar. The other two dihedral angles in the peptide bond determine the local shape assumed by the protein backbone.

Due to the chemical structure of the individual amino acids, the protein chain has directionality. The end of the protein with a free carboxyl group is known as the C-terminus or carboxy terminus, whereas the end with a free amino group is known as the N-terminus or amino terminus. Protein is generally used to refer to the complete biological molecule in a stable conformation, whereas peptide is generally reserved for a short amino acid oligomers often lacking a stable three-dimensional structure. However, the boundary between the two is not well defined and usually lies near 20–30 residues. Polypeptide can refer to any single linear chain of amino acids, usually regardless of length, but often implies an absence of a defined conformation..

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Biomolecule

A biomolecule is any organic molecule that is produced by living organisms, including large polymeric molecules such as proteins, polysaccharides, and nucleic acids as well as small molecules such as primary metabolites, secondary metabolitess, and natural products. As organic molecules, biomolecules consist primarily of carbon and hydrogen, nitrogen, and oxygen, and, to a smaller extent, phosphorus and sulfur. Other elements sometimes are incorporated but are much less common. Types of biomolecules A diverse range of biomolecules exist, including: * Small molecules: Lipid, phospholipid, glycolipid, sterol Vitamin Hormone, neurotransmitter Carbohydrate, sugar Disaccharide * Monomers: Amino acids Nucleotides Monosaccharides * Polymers: Peptides, oligopeptides, polypeptides, proteins Nucleic acids, i.e. DNA, RNA Oligosaccharides, polysaccharides (including cellulose) Lignin

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