Chemicals Talk

 PEPTIDES FUNCTIONS  Peptides from the Greek word means digested are short polymers of amino acid monomers linked by peptide bonds, the covalent chemical bonds formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule.  Peptides are distinguished from proteins on the basis of size, typically containing fewer than 50 monomer units. The shortest peptides are dipeptides consisting of two amino acids joined by a single peptide bond. There are also tripeptides, tetrapeptides etc. Amino acids which have been incorporated into a peptide are termed "residues"; every peptide has a N-terminus and C-terminus residues on the ends of the peptide. A polypeptide is a long, continuous, and unbranched peptide.   Proteins consist of one or more polypeptides arranged in a biologically functional way and are often bound to cofactors, or other proteins.  Long peptides such as amyloid beta can be considered proteins, wherea...

 PHYSICAL PROPERTIES  Solubility  Most of the amino acids are usually soluble in water and insoluble in organic solvents. Melting point Amino acids generally melt at higher temperatures, often above 200 Celsius. Taste  Amino acids may be sweet (Gly,Ala,Val), tasteless (Leu) or bitter (Arg, Ile), Monosodium glutamate (MSG; ajinomotto) is used as flavouring agent in food industry. Optical properties  All amino acids except glycine possess optical isomers due to the presence of asymmetric carbon atom. Some amino acids have a second asymmetric carbon e.g. isoleucine, threonine.  On heating to high temperatures, they decompose. Amino acids are colourless, crystalline solid. Peptide bond formation  Amino acids can connect with a peptide bond involving their amino and carboxylate groups. Covalent bond formed between the alpha-amino group of one amino acid and an alpha-carboxyl group of other forming -CO-NH- linkage.  Peptide bonds are planar and partiall...