what is p50?

[thehonya]

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"The P50 is the oxygen tension at which hemoglobin is 50% saturated".

But we know there's a lot of hemoglobin and hemoglobin has multiple heme groups. So is p50 the po2 at which 50% of hemoglobin is fully saturated, or where 100% of all hemoglobin is 50% saturated, or what?

 

[Incis0r]

P50, also known as PO2-50, is the partial pressure of oxygen at which 50% of hemoglobin is saturated.

A higher PO2-50 implies more oxygen is needed to saturate hemoglobin, which means that it is a rightward shift (less affinity between hemoglobin and oxygen).

A lower PO2-50 implies that hemoglobin saturates easily, which is a leftward shift (more affinity between hemoglobin and oxygen).

 

[thehonya]

that didn't help much at all, I already knew that

 

[DAT Destroyer]

"The P50 is the oxygen tension at which hemoglobin is 50% saturated".

But we know there's a lot of hemoglobin and hemoglobin has multiple heme groups. So is p50 the po2 at which 50% of hemoglobin is fully saturated, or where 100% of all hemoglobin is 50% saturated, or what?

This is a very good question. You were right the second time. P50 refers to the pressure of oxygen that is needed for half (50%) of each Hemoglobin molecule to be saturated with Oxygen. In other words, at P50, each molecule of Hemoglobin only carries 2 molecules of Oxygen instead of 4 molecules.

Hope this helps.