Download Answers amino acid

ERT106 Biochemistry
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Tutorial Amino Acid
1. Distinguish between amino acids, peptides, polypeptides
Amino Acids :
Polypeptides : is a polymer containing more than 50 amino acid residues
Protein : a protein is composed of one or more polypeptides chain
Peptide : is a polymer containing less than 50 amino acid residues
2. Draw the standard structure of amino acid
3. Draw the structure of amino acid at physiological pH (7)
At physiological pH (7)
- carboxyl group of an amino acid is unprotonated. conjugate base form (-COO-)
- amino group of an amino acid is protonated. in its conjugate acid form (+NH3)
4. define the term below :
i)
ii)
amphoteric – substances that can act as an acid or base (eg. Amino
acid)
zwitterion – neutral molecule which bear an equal number of positive
and negative charge
5. Describe how amino acids form peptide bond and disulfide bridge
 Peptide bonds are amide linkage (CO-NH) formed when the carboxyl group of
one amino acid react with amino group of another amino acid
 Two molecules of cysteine oxidized to form a cystine (molecule that contain
disulfide bond)