True about O2 binding to myoglobin

Ans. is 'b' i.e., More affinity than hemoglobin Myoglobin is present in higher concentration in red (slow) muscle fibers. Myoglobin has greater affinity for oxygen than hemoglobin and its P50 is only 5 mm Hg (as compared to P50 of hemoglobin which is about 26 mm Hg). Therefore, myoglobin-oxygen dissociation curve is shifted far to the left than Hb-O2 dissociation curve. It has shape of hyperbola as compared to sigmoid shape of Hb-O2 curve because it binds 1 molecule of 02 per mole (in comparison to Hb which binds 4 molecules of O2 per mole). The role of myoglobin is to bind O2 at very low PO2 and release them at even lower PO2, for example in exercising muscles where PO2 close to zero.