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Molecules
Stephen Repacholi
Proteins
Made from C H O N & sometimes S
 Long chains of amino acids (aa)
 Properties determined by the aa
sequence

Amino acids
~20 aa
 Glycine R=H
 Alanine R=CH3

R
O
H
H
N
amine
C
H
C
O H
carboxyl
Peptide bonding
H
H
R
N
C
H
C
O
O H
H
H
R
N
C
H
C
O
O H
Peptide bonding
H
H
R
N
C
H
C
O
O H
H
H
R
N
C
H
C
O
O H
Peptide bonding
H
H
R
N
C
H
C
O
H
H H
O
R
N
C
H
C
O
O H
Peptide bonding
H
H
R
N
C
C
O
H
H
R
N
C
H
C
O
O H
Peptide bond
H H
O
water
A condensation reaction
Peptide bonding
H
H
R
N
C
H
R
O
C
N
H
A dipeptide
C
H
C
O
O H
Primary structure
 The
sequence of aa is know as the
primary structure
 The aa chain is a polypeptide
Secondary structure
forms between the –COOH
and the -NH2 of adjacent aa
 This results in the chains folding:
 H-bonding
Secondary structure
-helix
-pleated sheet
Tertiary structure
 Bonding
between R-groups
gives rise to a 3D shape
 H-bonds =O HNaffected by temp & pH
 Ionic
bonds –NH3-COOaffected by pH
 Disulphide
bridge
--CH2S-SCH2affected by reducing agents
Quaternary structure
 Some
proteins have
more than one
polypeptide chain
 Each chain is held
together in a precise
structure
 eg Haemoglobin
Types of proteins
 Fibrous
proteins
 e.g.
collagen
 Insoluble
 structural
 Globular
proteins
 e.g.enzymes
 Soluble
 3D
shape
Functions of proteins
Enzymes –
 Transport –
 Movement –
 Cell recognition –
 Channels –
 Structure –
 Hormones –
 Protection –

Amylase
Haemoglobin
Actin & myosin
Antigens
Membrane proteins
Collagen & keratin
Insulin
Antibodies
The Human Genome Project

A multinational project aimed at sequencing
the entire human genome
 Visit the Human Genome Web site:

www.ornl.gov/hgmis/project/about.html
 www.sanger.ac.uk
Acknowledgements

Animated cell models used by kind
permission of The Virtual Cell website:

Feel free to use this presentation for
educational non-profit making purposes.