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What are proteins made from?

Proteins are polymers - large complex molecules composed of monomers. These are amino acids. A dipeptide is formed when two amino acids join together. A polypeptide is formed when one or more than two amino acids join together. Proteins are made of one or more polypeptides. 

Amino acid structure

All amino acids have the same general structure - a carboxyl group (COOH) and an amino group (NH2) attached to a carbon. The difference is the R (variable) group. 

         H2N - C - COOH

Polypeptide formation

Amino acids are linked together by condensation reactions to form dipeptides and polypeptides. A molecule of water is released during the reaction. The bonds formed are called peptide bonds. A bond forms between amino group and carboxyl group of amino acid. The reverse reaction adds a molecule of water to break the bond - hydrolysis. 

Protein Structure

Primary Structure

Sequence of amino acids in the polypeptide chain. Held together by peptide bonds between the amino acids.

Secondary Structure

Polypeptide chain doesn't remain flat and straight. Hydrogen bonds form between the NH and CO groups of the amino acids in the chain. This makes it


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