Question

Which of the following statements about the molecular structure of antigens is correct? Multiple Choice

They have molecular weights of around 1000.

They are usually made of lipids.

They have one antigenic determinant (epitope).

They are made up of many antigenic determinants (epitopes).

• a whole bacterial cell.

• all of the combined antigenic determinants on a bacterial cell.

• one epitope on the bacterial cell.

• the bacterial cell's DNA.

Many different antibodies can be made against a single antigen.

• False

• True

Choose all the characteristics that are true about "active immunity."

• It protects the body against a new infection thanks to antibodies developed by the host during the first exposure to the antigen.It protects the body against a new infection thanks to antibodies developed by the host during the first exposure to the antigen.

• It requires several days to develop.It requires several days to develop.

• It can last for a relatively long time, sometimes for life.It can last for a relatively long time, sometimes for life.

• Active immunity can be stimulated only by artificial means.

Answer 1

*) Molecular structure of antigens:

Molecular weight : 14000 to 6,00,000 dalton.

Usually made up of protein and polysaccharides.

Antibody binds to epitope present on antigen.

All of the combined antigenic determinants on bacterial cell.

*) True. Many antibodies can be made against an antigen.

*) Active immunity:

Protects the body against new infection.

Antibodies are developed by the host.

Requires several days to develop.

Can last for longer time.