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.