what are peptides

8/12/2019 What Are Peptides

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What are Peptides ?

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Peptides are short chains of amino acidsmonomer that are linked by amidebonds. Amide bonds are also known aspeptide bond and both are used

interchangeably to denote one another.One molecule of water is eliminated fromthe condensation of amino acids to formpeptide. The result is peptide or aminebonds.



Either end of dipeptide can react to giverise to tripeptide. The tripeptide in turncan condense with another amino acidand so on.

This keeps giving rise to formations oflong chains of amino acids. For instance,insulin, which is a common protein, has51 amino acids units in two linkedchains.



Peptides are so numerous because oftheir ability to be synthesized into verylong chains. Peptides and proteins aresimilar in structure but there are

noticeable differences between them. Aprotein is polymer of amino acids. It is apoly peptide containing several aminoacids linked together.



Types of Peptides The shortest peptides known aredipeptides. It consists of two amino acidslinked together by a single peptide bondwith the loss of water molecule. Thebiosynthesis of peptide bonds alwaysrequires an input of free energy. Peptidesbonds are quite stable kinetically. Thelifetime of a peptide bond in an aqueoussolution in the absence a catalyst is closeto a thousand years.



Tripeptide is another type of peptides.Glutathione is one the most importantand well known tripeptide. It iscommonly found in significant

concentrations in all tissues. It containsglutamic acid, cysteine, and glycine.Instead of the usual backbone that ischaracteristics of peptides, the carboxylacid side chain is part of the backbonepeptide structure. The normal carboxylgroup is the so called side chain in thiscase.



Polypeptide chain consists of a regularlyrepeating part. This is the main chain. Itcan also be referred to as the backboneof the polypeptides. It is very rich in

hydrogen bonding potential. Apart fromthe backbone, there is also the variablepart. This is made up of distinctive sidechains.



Each residue of a polypeptide chainconsists of carbonyl group. The carbonylgroup is good hydrogen-bond acceptorwith the exception of Proline which is an

excellent donor of hydrogen bond. Thesetwo groups highly interact with eachother. They also interact with thefunctional groups present on the sidechains. This interaction is of greatimportance in stabilizing the polypeptidechains



Most natural polypeptide chains aremade up of 50 and 2000 amino acidresidues. They are commonly known asproteins. When the chains are small, it is

called Oligopeptides or simply peptides.Examination of the geometry ofpolypeptides reveals a number ofoutstanding characteristics. Theseinclude the following:



Peptides bond are mainly planar.They have considerable double bondcharacter. This prevent rotation aboutthis bondInability of the bonds to rotate accountfor planarityTrans and cis configuration is possible for

a peptide bond. However, the mostcommonly observed is transconfiguration.



Classes of Peptides Depending on how they are produced,Peptides are usually divided into severalclasses. The classes of Peptides are asfollows:Milk peptidesRibosomal peptides

Nonribosomal peptides



Difference between Peptides andProteins Peptides can be distinguished fromproteins on the basis of size. A peptide isgenerally believed to have less than 70amino acids. Proteins usually consist ofone or more polypeptides and this givesrise to long chains. Protein can simply bedefined as a polymer of amino acids.



When amino acids are incorporated intopeptides, they are called residues. This isdue to the release of either a hydrogenion from the amine end or a hydroxyl ion

from the carboxyl end. At times, bothmay occur as there is release of watermolecules during the formation of eachamide bond.



There are so many things to know aboutpeptides. The subsequent articles willaddress uses, advantages, importanceand benefits of peptides to human life.

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