Leftward shift on the oxygen affinity curve would cause what change in oxygen unloading to tissues?

• A. Increased unloading
• B. Decreased unloading
• C. No change
• D. Unloading increases during hypoxia

Answer: (B)

A leftward shift on the oxygen-hemoglobin dissociation curve means hemoglobin has a higher affinity for oxygen. Because the tissues typically have lower PO2, Hb will hold onto O2 more tightly and release less of it to the tissues. So oxygen unloading to the tissues decreases. In other words, higher affinity makes oxygen harder to release where it’s needed. A rightward shift does the opposite, promoting unloading. The other statements don’t fit because they describe scenarios where unloading would increase or stay the same, which doesn’t align with increased oxygen affinity.