# What is the state of aggregation (gas, liquid) of oxygen in blood?

Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.

When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test

Also, how does the lungs convert the gas into something that is compatible to be in blood?

References: Amount of Oxygen in the Blood

• Very highly related, might resolve your issue: biology.stackexchange.com/questions/8611/… – M.A.R. Jun 26 '15 at 14:28
• @M.A.Ramezani I was actually thinking where to post this question, whether in Chem or Bio. The above post definitely covers majority of the chemistry required. My main questions were, how would compounds exist in blood in gas form, if so? What sort of a conversion takes place in alveolis to capillaries. Care to post an answer? :) – bonCodigo Jun 26 '15 at 14:54
• unfortunately, I don't have the sufficient time right now, I might strike the problem in the future. Also, considering your comments below, I think that question on bio.SE does answer your question. Most of the oxygen in blood becomes a "part" of a complex. – M.A.R. Jun 26 '15 at 15:13
• The oxygen isn't actually pushed into the bloodstream, it flows naturally, via diffusion, due to the concentration gradient (concentration in alveolar air is higher then on the venous blood arriving at the lung), plus its high hemoglobin affinity. – heltonbiker Jun 26 '15 at 19:34

Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.

Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.

Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.

• So the knowledge is saying in theory (practically/reality...) there won't be oxygen as it's in blood and pure molecule or compound can't be found - for stabilising reasons and other given reasons. Acceptable. – bonCodigo Jul 13 '17 at 4:23

We inhale a lot of other atmospheric gases with oxygen. The mixture of gases go to the sacs in our lungs which is crawling with lots of blood capillaries.
The blood (specifically RBCs) contains a pigmented substance called haemoglobin, each of them can bind 4 oxygen molecules (if working normally) forming a substance named Oxyhaemoglobin.
This is then carried through blood vessels to the cells in the body.

The binding phenomena of oxygen with haemoglobin is reversible in nature. That is, at high oxygen concentration oxygen binds with haemoglobin to form oxyhaemoglobin, but when the oxygen concentration decreases (in cells, which are in need of oxygen) the oxygen again dissociates from haemoglobin.

The overview thus provided here, if you wish to be more specific about chemical reactions you may find this useful.

• I don't mean to be rude. Can you answer this from a chemistry perspective? e.g. what happens to Oxygen state from alveoli to Capillaries? – bonCodigo Jun 26 '15 at 14:50
• Simple diffusion, based on the partial pressure. It goes from high pO2 (alveoli) to low pO2(blood capilaries) zone. @bonCodigo – diffracteD Jun 26 '15 at 16:02