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.