Why does hemoglobin accept oxygen molecules in the lungs but give up oxygen molecules in tissue?

Answer 1

In the lungs where the oxygen concentration is high the binding of oxygen tohemoglobin is high. In respiring tissue where the oxygen levels are low and the CO2 levels are high the affinity of hemoglobin for oxygen is reduced and so the oxygen comes off the hemoglobin and is used by the cells. The driving force for this is the Bohr Effect whereby CO2 produced by the respiring cells dissolves in the blood as follows

CO2 + CO2 --> H2CO3 --> H+ + HCO3-. The H+ produced bind to the hemoglobin and in doing so displace the oxygen

Answer 2

For the answer to your question, you first need to know the basic principle of diffusion and partial pressure of gases.

In simple words, diffusion across a membrane means movement of a molecule from one side of the membrane to the other with the help of its own kinetic energy due to random motion.Now, this movement always takes place from its high concentration chamber to the low concentration chamber, until both the chambers gain equal concentration of that particular substance or molecule. (note that, the membrane has to be permeable to that substance)

In case of gases, pressure is a more convenient unit that its concentration and pressure exerted by a gas is proportion to its concentration.

So, in case of gases, diffusion takes place from high pressure chamber to low pressure chamber.

Now, Air is a mixture of gases, so if we want to consider transport of oxygen, we take into account only the pressure exerted by oxygen alone in the mixture of gases. This is called Partial pressure of oxygen (pO2)

Therefore, oxygen molecules will diffuse from a zone of higher pO2 to a zone of lower pO2.

NOW THAT YOU KNW THE BASICS, HERE IS THE ANSWER TO YOUR QUESTION:

In the lungs, oxygen diffuses from the alveoli into the pulmonary capillary blood because the pO2 in the alveoli is greater than the pO2 in the pulmonary capillary blood.

In the other tissues of the body, a higher pO2 in blood than in the tissues causes oxygen to diffuse into the surrounding cells.

The oxygen molecule combines loosely and reversibly with the heme portion

of hemoglobin.

When pO2 is high, as in the pulmonary capillaries, oxygen binds with the hemoglobin,

but when pO2 is low, as in the tissue capillaries, oxygen is

released from the hemoglobin.

Answer 3

hemoglobin contains iron and the iron absorbs the oxygen and releases it. the iron also causes the blood cell to be red

Answer 4

why? because they live in high altitude conditions (mountainous, Andes), so a high affinity is needed.