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Name of protein

Haemoglobin

Type of protein:
Key properties
1
...
simple/conjugated
Globular
- responsible for carrying
Conjugated
oxygen from the air in the
lungs to all the cells in the
body via red blood cells
present in the blood

How it is formed

Where it’s found

- made up of 4 polypeptide chains: two alpha chains and
two beta chains
- total of 574 amino acids are present in one molecule of
haemoglobin
- alpha and beta chains form an alpha helix and they are
held together by hydrogen bonding
- contains a heme group (containing the prosthetic group
Fe2+)

- red blood cells

- the pancreas

Insulin

Globular
Simple

- soluble in water
- insoluble in alcohol

- an insulin molecule consists of two polypeptide chains,
which are held together by disulphide bonds
- the A chain begins with a section of alpha-helix, and the B
chain ends with a section of beta-pleated sheet
- amino acids with hydrophilic R groups are on the outside
of the molecule, which makes it soluble in water

Catalase

Globular
Conjugated

- works best at neutral pH
- breaks down hydrogen
peroxide which is a common
by product of metabolism
and is damaging to cells

- quaternary protein containing four haem prosthetic
groups
- the presence of iron II ions in the prosthetic groups allow
catalase to interact with hydrogen peroxide and speed up
its breakdown

- the liver

Types of
bonding
involved
- hydrogen
bonding

- disulphide
bonds

- hydrogen
bonds

Pepsin

Globular
Simple

- protease enzyme
- works best in acidic
conditions
- optimum pH is around 2

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