Question

how do we breathe in exactly the oxygen molecules while there are many other gases around the pressure of oxygen?

Answer 1

breathing happens because of difference in pressure within our system and atmosphere so wont there be other gases which can enter via the pressure gradient?

Answer 2

Other gasses do enter the system. ask any suba diver one of the bigest fears when diving is getting nitrogen bubbles in their blood system which at the very least will be highly uncomfortable. If our system only pulled o2 out of the air we wouldn't have to worry about getting poisined when subjected to different gasses.

Answer 3

ya wat is that mechanism by which we separate out the oxygen alone from mixture of other gases?

Answer 4

It's been a while since biology but i'm pretty sure gass transfusion happens via a key lock system in the red blood celss which takes place in the lungs.

Answer 5

alveolies in lungs only require qxygen.transfusion of oxygen only oiccurs at walls of alveoli

Answer 6

Key and lock mechanism is right
hemoglobin or haemoglobin is the essential protein component of red blood cells found in the blood, and is responsible for transportation of oxygen. These protein contains a centre apparatus that utilizes iron (Fe2+/Fe3+) to lock on to specific molecular oxygen molecules by opposite charge attraction, this centre is an organic compound known as a porphyrin ring. Simply put, the specificity for oxygen is achieved by the spacing arrangement of the ring and where oxygen binds, this produces a very 'snug' fit on the ring when oxygen binds. Nitrogen on the other hand is small enough to get inside the hemoglobin, but not large enough (in terms of atomic radius) to produce a nice fit in this binding spot, so its gets diffused out eventually even if it does get inside these binding spots. So the red blood cells have good affinity for oxygen but not for nitrogen.

Conversely, carbon monoxide (C triplebond O) has extremely high affinity hemoglobin (red blood cells) even higher than oxygen (around 200x more affinity). The chemical reasoning behind this is that the triple bond between the C and O results in an electronic configuration of CO to be highly negative which is attracted by the positive iron centre contained in the porphyrin (they are like opposite poles of a magnet), the CO also produces a good fit in this porhyrin centre. It essentially forms a permanent bond to the red blood cells such that they can no longer bind to oxygen, and if red blood cells can no longer transport oxygen, vital functions of the blood cell is disrupted. So that's why carbon monoxide is so lethal to humans. Cyanide works also in a similar fashion if I'm not mistaken.

Hope that helps