Amino acids
After studying this section you should be able to:
- describe the acid–base properties of amino acids and the formation of zwitterions
- explain the formation of polypeptides and proteins as condensation polymers of amino acids
- describe the acid hydrolysis of proteins and peptides
Amino acids
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- There are 22 naturally occurring amino acids.
Acid–base properties of amino acids
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- At the isoelectric point, the amino acids exist in equilibrium with its zwitterion form.
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- Because of their reactions with strong acids and strong bases,amino acids act as buffers and help to stabilise the pH of living systems.
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Physical properties of amino acids
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Polypeptides and proteins
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Each peptide link forms:
- between the carboxyl group of glycine and the amino group of alanine
- with loss of a water molecule in a condensation reaction.
Further condensation reactions between amino acids build up a polypeptide or protein.
- For each amino acid added to a protein chain one water molecule is lost.
- Most common proteins contain more than 100 amino acids.
- Each protein has a unique sequence of amino acids and a complex three-dimensional shape held together by intermolecular bonds including hydrogen bonds.
- A polypeptide is the name given to a short chain of amino acids linked by peptide bonds. A protein is simply the name given to a longchain polypeptide.
Hydrolysis of proteins
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PROGRESS CHECK
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