Peptide bond
Peptide bonds (also known as amide bonds[1]) are the bonds that are found between two monomer units of amino acids in a polypeptide chain. They are created through condensation reactions in which a molecule of water (H2O) is removed. The water is made by combining a hydroxyl group (OH) of one amino acid with an hydrogen from the amino group (NH2). The two amino acids then become linked by a new peptide bond and is called a dipeptide. Polypeptide chains are made up of amino acids linked together by these peptide bonds and this linear sequence forms the the primary sturcture of a protein. The formation of a peptide bond occurs during protein synthesis whereby which ribosomes (consisting of one small subunit and one large subunit) translate an mRNA sequence coding for the protein ( translation ).
The peptide bond is a stable covalent bond and is said to be a rigid planar bond because it has a partial double bond character. The evidence that shows this partial double bond character is from the length of the bond. It is 0.13 Angstrom shorter than the C-N single bond yet not as short as a double bond[2].
Peptide bonds can also be easily broken by hydolysis (amide hydrolysis). This is completely the opposite to condensation, whereby water is added to the dipeptide/polypeptide and the peptide bond breaks to give its two constituent amino acids.
A peptide bond is a kind of linkage between two amino acids. It is also known as an amide bond. A peptide bond connects two amino acids, forming a dipeptide, and is associated with the loss of a water molecule. This process is called a condensation reaction. One perhaps surprising fact about peptide bonds is that they are very kinetically stable, in fact a peptide bond in a solution will last 1000 years, if no catalyst is present to disrupt it.
Many amino acids can be connected via peptide bonds, making a polypeptide. Each amino acid is then called a residue as it forms part of the polypeptide[3]. The ends of a polypeptide chain will be different because an alpha amino group is present at one end and an alpha carboxyl group present at the other. This gives the polypeptide chain polarity[4].
References
- ↑ Berg,JM.Tymoczko, JL.and Stryer, L.,2007.Biochemistry. 6th Edition. New York: Sara Tenney.
- ↑ Voet, Voet, Pratt (2008) Principles of Biochemistry, 3rd Ed. Wiley. 127
- ↑ Berg, Tymoczko, Stryer, Biochemistry 6th ed, W.H. Freeman and Company, 2007
- ↑ Alberts, Johnson, Lewis, Raff, Roberts, Walter. Molecular Biology of The Cell 2008, Garland Science.