If a solution contains 1 x 106 hb molecules, how many o2 binding sites are available? if the solution of hb is 50% saturated with o2, how many binding sites are occupied by o2? if the hb solution is 23% saturated with o2, how many binding sites are occupied by o2?

Actually each molecule of Hb can bind four oxygen molecules. So given 1 x 10^6 Hb, so there are 4 x 10^6 binding sites available.

If only 50% of the Hb are bound, so this means that 2 x 10^6 binding sites are occupied by O2. However we must remember that hemoglobin binding is an all-or-nothing phenomenon. Meaning that each molecule of Hb binds four molecules of oxygen or zero at all.

If 23% is saturated, so the number of binding sites occupied is 0.92 x 10^6 binding sites or 9.2 x 10^5 binding sites.