I found this question in a book, but there was no answer for it. It got me thinking where else does facilitated/passive diffusion and active transport occur in the body. I was hoping you guys can give me some examples. Thanks!

"The exchange of oxygen for carbon dioxide and water vapor at the alveolus occurs by.."

A Active Transport
B Passive Diffusion
C Facilitated Diffusion

I think its B because theres no transport protein(facilitated) involved, and it doesn't require ATP(active).

Sounds good to me

Yeap! Gas exchange in the respiratory system is always a passive process (Doesn't require energy expenditure). Why is it not facilitated diffusion?
Because it's occuring across the alveoli membrane without the need of any additional channels or transport proteins.

Plus O2 and CO2 are small, non-polar molecules that cross plasma membranes readily. They simply cross the boundary, moving down the concentration gradient.

active transport: ex. the sodium/potassium pump (pumps 3 K into cell, 2 Na out, and costs ATP) (low-->high concentration)

passive diffusion: ex. co2, o2 entering/exiting cell. osmosis is also diffusion (water diffusion) (high-->low concentration)

facilitated diffusion: ex. movement of K through an pore. the pore is "facilitating" it. (high-->low concentration)

active transport: ex. the sodium/potassium pump (pumps 3 K into cell, 2 Na out, and costs ATP) (low-->high concentration)

passive diffusion: ex. co2, o2 entering/exiting cell. osmosis is also diffusion (water diffusion) (high-->low concentration)

facilitated diffusion: ex. movement of K through an pore. the pore is "facilitating" it. (high-->low concentration)


hmm...i thought numbers are vice versa.

hmm...i thought numbers are vice versa.

Yep, you're correct. It's definitely 3 Na+ out/2 K+ in

Yeap! Gas exchange in the respiratory system is always a passive process (Doesn't require energy expenditure). Why is it not facilitated diffusion?
Because it's occuring across the alveoli membrane without the need of any additional channels or transport proteins.

I quoted nze82 bc it is the main reason. passive diffusion is the spontaneous gas exchange, without the use of any energy or effort by the body, between the gas in the alveolar and the blood in the capillaries in the lungs; and also it has only one layer of very thin epithelial cell in the alveoli.
(For helpful information)Perfusion is the process by which the cardiovascular system pumps blood throughout the lungs.

You can also think about it as small molecules moving down their concentration gradient. The high atmospheric pressure of O2 allows it to go down its concentration gradient (diffuse in the alveoli which has a lower O2 pressure), and vice versa. The same goes for CO2.

hmm...i thought numbers are vice versa.

yeah my bad, i was just tryin to set off the curve :laugh:

jk.

2 k in and 3 na out causes the inside to be relatively negative.

I found this question in a book, but there was no answer for it. It got me thinking where else does facilitated/passive diffusion and active transport occur in the body. I was hoping you guys can give me some examples. Thanks!

"The exchange of oxygen for carbon dioxide and water vapor at the alveolus occurs by.."

A Active Transport
B Passive Diffusion
C Facilitated Diffusion

I think its B because theres no transport protein(facilitated) involved, and it doesn't require ATP(active).

Water vapor? Shouldn't that just be oxygen.


Also, on the cellular level water usually undergoes facilitated diffusion by aquaporin. The lungs are def. passive diffusion tho. I just don't think it should be water vapor, it's CO2 and O2 that transport, not water.