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Amino acid. Structure of a typical L -alpha-amino acid in the "neutral" form. Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. [1] Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. [2]
An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms, the nine amino acids humans cannot synthesize are valine, isoleucine, leucine, methionine ...
Serine (symbol Ser or S) [3][4] is an α- amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − NH+. 3 form under biological conditions), a carboxyl group (which is in the deprotonated − COO−. form under biological conditions), and a side chain consisting of a hydroxymethyl ...
Protein is a nutrient needed by the human body for growth and maintenance. Aside from water, proteins are the most abundant kind of molecules in the body. Protein can be found in all cells of the body and is the major structural component of all cells in the body, especially muscle. This also includes body organs, hair and skin.
A conservative replacement (also called a conservative mutation or a conservative substitution or a homologous replacement) is an amino acid replacement in a protein that changes a given amino acid to a different amino acid with similar biochemical properties (e.g. charge, hydrophobicity and size). [1][2] Conversely, a radical replacement, or ...
Aromatic amino acids, excepting histidine, absorb ultraviolet light above and beyond 250 nm and will fluoresce under these conditions. This characteristic is used in quantitative analysis, notably in determining the concentrations of these amino acids in solution. [1] [2] Most proteins absorb at 280 nm due to the presence of tyrosine and ...
Arginine is the amino acid with the formula (H 2 N)(HN)CN(H)(CH 2) 3 CH(NH 2)CO 2 H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO 2 −) and both the amino and guanidino groups are protonated, resulting in a cation.
A table comparing four different scales for the hydrophobicity of an amino acid residue in a protein with the most hydrophobic amino acids on the top. A number of different hydrophobicity scales have been developed. [3] [1] [7] [8] [9] The Expasy Protscale website lists a total of 22 hydrophobicity scales. [10]