Wednesday, July 11, 2012

STPM Biology - chapter 1: Revision essay question 4

4. Explain the formation of peptide bond.


Answer:



The molecules must be orientated so that the carboxylic acid group of one can react with the amine group of the other. For example, two amino acids (glycine) combining through the formation of a peptide bond to form a dipeptide. 




Any number of amino acids can be joined together in chains of 50 amino acids called peptides, 50-100 amino acids called polypeptides, and over 100 amino acids called proteins. A number of hormones, antibiotics, antitumor agents and neurotransmitters are peptides (proteins).
A peptide bond can be broken down by hydrolysis (the adding of water). The peptide bonds that are formed within proteins have a tendency to break spontaneously when subjected to the presence of water (meta-stable bonds) releasing about 10 kJ/mol of free energy. This process, however, is very slow. Living organisms use enzymes to broken down or to form peptide bonds. The wavelength of absorbance for a peptide bond is 190-230 nm.

Assignment submitted by L.Y., Kong,  S. H., Lim, S. C., Soo, C. W. Tan and C.C.,Teh 2011/2012 (IBM)

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