Antibody Structure and Function Each antibody is produced

Antibody Structure and Function

Each antibody is produced by lymphocytes (specialised white cells) as a result of exposure to specific chemical substances (mainly proteins and carbohydrates) called antigens, usually on the outside of an invading organism. They are able to react to form an antigen-antibody complex. At the molecular level, antibodies are known to be shaped like the letter Y, with a reactive site at the tip of each branch, so that antibodies can become attached to antigens on the basis of their molecular shape, rather like an enzyme and substrate. This can cause the infecting microorganisms to stick together, and neutralises them until they are taken away and dealt with by other white cells.

Effector mechanisms 3 of 38 © Boardworks Ltd 2008

Antibody structure 4 of 38 © Boardworks Ltd 2008

Antibody Structure The specificity of the antibody depends on its variable regions Antigen Variable regions (red) The constant regions are the same for all antibodies Light chain Hinge region Disulphide bridges Constant regions (blue) Heavy chain Each antibody has a different shaped variable region (Due different amino acid sequences) that is complementary to one specific antigen

Antigen binding site The structure of an antibody All antibodies are proteins. This means that they are made up of a long chain of amino-acids which are arranged into a complex structure.

How do Antibodies Work? Using the templates sheet, make a poster explaining how antibodies can fight infection Key Terms: § Agglutination §Neutralisation

Agglutination § Antibodies can cause microbes to stick together § This makes it easier for phagocytes to engulf them

Neutralisation § Some pathogens make us ill by producing toxins § Some antibodies work by neutralising these toxins

§ Viruses have proteins on their surface which recognise and bind to receptors on the surface of the host cell § This is how many viruses enter their host cell § Antibodies can bind to viruses and stop them attaching to their host cells

PATHOGENS ANTIBODIES TOXINS

Questions 1. In what ways are antibodies similar to enzymes? 2. What is formed between an antibody and a pathogen? 3. Complete the key words for this lesson: – – – – – A____-_____ T_______ s_____ P_____ c____ V_____ r_____ Ag_________ N__________ A_____ a_____ D_____ b____ Q______ s____ Add any other key words that have been missed.