Proteins

Structure of amino acids

• amino acids combine to form a polypeptide
• polypeptides can be combined to form proteins
• evidence for evolution: the same 20 amino acids occur in all living organisms
• every amino acid has a central carbon atom to which are attached 4 different groups:

1. amino group (-NH2): a basic group which gives the amino acid the amino part of the name

2. carboxyl group (-COOH): acidic group

3. hydrogen atom (-H)

4. R (side) group: a variety of different chemical groups. Each amino acid has a different R group.

Formaton of a peptide bond

• amino acid monomers can come together to form a dipeptide in a condensation reaction
• the water is made by combining an -OH from the carboxyl group with an -H from the amino group of another amino acid
• the 2 amino acids then become linked by a peptide bond between the C atom of one amino acid and the N one of another
• the peptide bond of a dipeptide can be broken down by hydrolysis

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