# Antibodies

Source: https://projectalevel.co.uk/biology/immunity/antibodies

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Antibodies are:

- Globular glycoproteins.
- Belong to plasma protein group called immunoglobulins.
- Basic molecule has: 2 long and 2 short polypeptide chains with a dilsulphide bridge holding them together.
- Each molecule has at least two identical antigen binding sites in its variable region.
- Flexible hinge allows antibody to bind to antigen.

They work by:

- Punching holes in bacteria cell wall (effecting osmosis) and make them burst.
- Attaching to flagella so bacteria are less active.
- Cause bacteria to clump together so less chance of spreading.
- Combine with toxins to make them harmless.
- Coat pathogen so phagocytes are attracted and ingest them.
- Combine with viruses and bacterial toxins to prevent them entering a cell.