A solution has 4 pentomeric IgM antibodies per microliter.What concentration of antigen molecules is necessary for the solution to be in the zone of equivalence? The antigen has 4 identical epitopes on each molecule.

Question

Quizplus · Accepted Answer

In order for a solution to be in the zone of equivalence, the concentration of antigen molecules should be equal to the concentration of antibody molecules with binding sites for the antigen. As each pentomeric IgM antibody has 10 binding sites, we need to find the concentration of antigen molecules that will have 4 x 10 = 40 binding sites per microliter.

Since the antigen has 4 identical epitopes on each molecule, we can calculate the concentration of antigen molecules necessary as follows: 
1 microliter solution = 4 pentomeric IgM antibodies x 10 binding sites per antibody = 40 binding sites
Each antigen molecule has 4 epitopes, so we can assume that each antigen molecule can bind to 4 binding sites. Thus, 
40 binding sites / 4 epitopes per antigen molecule = 10 antigen molecules per microliter

Therefore, the correct choice is C) 10 antigen molecules per microliter.

A Solution Has 4 Pentomeric IgM Antibodies Per Microliter