IMMUNOLOGY HELP!PLEASE!

[pinkypig]

I have a few questions that i realy need help with....

1) The basic Ig unit is composed of:
Non-covalently bound polypeptide chains
2 identical heavy and 2 identical light chains
2 different heavy and 2 identical light chains
2 identical heavy and 2 different light chains
2 different heavy and 2 different light chains

I think it is 2 identical heavy and 2 indentical light?

2) Cleavage of IgG by papain produces which of the following:
A Fab fragment
Monovalent antigen binding fragments
Isolated heavy chains
F(ab')2
Isolated light chains

I think it could be a fab fragment but not sure!

3) Which ONE of the following statements is INCORRECT? Affinity is:

A measure of the strength of the binding of antigen to antibody
Related to specificity
Related to the free energy change of the Ag/Ab interaction
Always equal to avidity
The association constant of the Ag/Ab equilibrium

4) Select the ONE answer that is CORRECT. IgD

Is pentameric
Is abundant in milk
Is present mainly as a surface receptor on B-cells
Is present with unusual frequency in myelomas
Is resistant to proteolytic degradation

5) Select the ONE answer that is CORRECT. IgA in seromucus secretions:

Is dimeric
Cannot bind to neutrophils
Has no J-chain
Has no secretory piece
Activates the classical complement pathway


Could you let me know which ones you think are correct and also if you could provide information to back up the answers please?

Thanks