How does a cell know if O2 is being diffused with it or CO2?


I just read about diffusion today and I want to know how does a cell(plasma membrane to be more specific)know if O2 is being passing through it or CO2?

In: Biology

Chemistry. Molecular oxygen is very reactive and will rapidly bind with hydrogen given the chance, which is exactly what we use it for. We breathe in oxygen specifically to take away waste protons that would otherwise build up and burn us to death with acid.

Carbon dioxide in water disassociates and binds with the water to become carbonic acid so rather than helping to get rid of the acidity it will actually raise it

My vague understanding is this:
Diffusion occurs because both oxygen and CO2 naturally balances with itself. So oxygen tends to spread to where there is less oxygen (outside to inside of cell) as with CO2 except there is more CO2 inside the cell then outside of it.

As far how a cell “knows”, not sure but the cell doesn’t actively do this. It’s passively doing it due to physics/chemistry.

I’m no expert so feel free to correct me friends.

There is no active process involved. None of the cells “know” about O2 and CO2. The way it works is this – the mitochondria consumes nutrients and O2 to produce energy (and CO2 as a waste product). That causes the concentration of O2 in the proximity to drop and the CO2 concentration to rise. Then it’s all about the chemical process of diffusion – particles tend to move from an area of higher concentration to an area of lower concentration. In blood, there’s higher O2 concentration than in the proximity of the mitochondria, therefore O2 moves from the blood to the mitochondria. The reverse goes for CO2. In the lungs the situation is opposite – in the alveoli there’s higher concentration of O2 than in the blood and lower CO2 concentration.