a-amino acids are the building blocks for polypeptides and proteins. All aminocids except proline have the following structure:
| R- CH-COOH | |
| ___| | |
| NH2 |
in w|hich the carbon Ca
is attached to both an amino (-NH2) and a carboxyl group (-COOH)
and R is the side chain.
There are a total of 20 amino acids. amino acid can be divided into 4 categories depending on the side chain side chain. Under physiological conditions the amino acids are in the charged form.
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| The amino acids have these features in common: The carboxyl group. The amino group. (Proline is an imino acid.) The a-carbon. The a-hydrogen The b-carbon. (Glycine has no side-chain.) The side chain (or R-group). 
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The carboxyl group. |
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