O2 diffusion

[thunder5]

if you take a deep breath in and hold it, will the O2 diffuse into or out of your blood?

[gen2]

Answer depends at what level you are studying.

Oxygen will always diffuse IN to the blood. That is how the lungs work.

As you hold your breath, oxygen will diffuse into the blood until the concentration of oxygen is the same on both sides. Since there is no source of oxygen in the body, the level of oxygen can never get higher than the level in the lungs and so cannot diffuse out.

To answer your question at a higher level, oxygen diffuses both IN and OUT of the blood at all times. At a molecular level, oxygen molecules pass/diffuse both ways through the membranous lining of the lungs. If the concentration of oxygen molecules is the same on both sides then as many pass in as pass out and there is no net change. When there is more oxygen in the air in the lungs then the net flow will be INTO the blood. The net flow can never be OUT as there is no mechanism to raise the blood oxygen level above that of the air being breathed.

[peanut273]

ok.

its both. blood is biconcaved shaped &suited to its function to carry oxygen, however when we breath in it goes IN to the blood...But then will leave ano go OUT of the Veins or venules as the oxygen is being supplied to other tissues or majour organs which need oxygen.