Effect of O2 concentration on the combination of haemoglobin with O2 in lungs

Haemoglobin (Hb) is a protein found in red blood cells that is responsible for transporting oxygen (O2) from the lungs to other tissues in the body. The combination of Hb with O2 in the lungs is an important process that can be influenced by the concentration of O2 in the blood.

Increased O2 concentration in blood
When the concentration of O2 in the blood is high, such as in the lungs, Hb has a high affinity for O2 and readily binds to it. This is because Hb undergoes a conformational change when it binds to O2, which increases its affinity for more O2 molecules. This process is known as cooperative binding, and it allows Hb to function efficiently in transporting O2 to tissues that need it.

Decreased O2 concentration in blood
Conversely, when the concentration of O2 in the blood is low, such as in tissues that are using O2 for metabolism, Hb releases its bound O2 molecules. This is because the conformational change that occurs when Hb binds to O2 is reversed in the absence of O2. This allows Hb to unload O2 where it is needed most.

Conclusion
Overall, the combination of Hb with O2 in the lungs is promoted by an increased concentration of O2 in the blood. This process is important for efficient O2 transport to tissues in the body. Conversely, a decreased concentration of O2 in the blood promotes the release of O2 from Hb in tissues where it is needed.

B) increased in O2 conc. in lungs but decrease in O2 conc. in blood