Proteins

1
Proteins

• are compounds of carbon, hydrogen, oxygen,
  nitrogen and sometimes sulphur, phosphorus
• amino acids
• unit of proteins
• about 20 different types
• essential and non-essential types

2
An amino acid molecules
R
COOH carboxyl group
C
H2N amino group
H
3
The condensation and hydrolysis of a polypeptide
4
1
2
5
3
hydrolysis
condensation
1
2
3
4
5
4
Condensation of two amino acid to form a dipeptide
O
R1
H
H
C
H2N
C
N
C
COOH
OH H
H
R2
H2O
R1
H
O
C
H2N
C
COOH
C---N
H
H
R2
5
Functions of proteins

• components of cell membranes and cytoplasm
• for growth and repair of body cells
• for making enzymes, hormones, antibodies and
  haemoglobin
• provide energy during starvation
• excess protein is under deamination in the liver
• deficiency disease Kwashiorkor

6
Test for proteins / Biuret test
egg white solution
1 cm3 NaOH solution
Put CuSO2 solution drop by drop, and shake the
mixture after addition of each drop
Positive result purple colour