urea--will diffuse through plasma membrane?

[thebillsfan]

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it's small enough, but it is sort of polar. I read somewhere that urea diffuses through the membrane without the help of a transport protein. is that accurate?

 

[Charles_Carmichael]

It shouldn't be able to diffuse through the membrane. For example, in the nephron, urea can be reabsorbed from the collecting duct in the presence of ADH but not via diffusion through the membrane. A transporter must be present; otherwise, urea reabsorption wouldn't be regulated since it would passively diffuse through the membrane all the time depending on the concentration gradient (which is high in the collecting duct and low in the interstitial fluid).

 

[Hemichordate]

I heard this question too. I believe it asked whether answer choice did not require ATP, so urea transport does not require ATP right?

 

[OMTlover]

I heard this question too. I believe it asked whether answer choice did not require ATP, so urea transport does not require ATP right?

At physiological pH Urea can cross via passive transport, provided its nitrogens are not protonated. It is a fairly small polar molecule.

 

[thebillsfan]

this is probably overthinking, but it doesnt matter that atp was required to create the transport proteins or anything? just making sure =)

 

[OMTlover]

this is probably overthinking, but it doesnt matter that atp was required to create the transport proteins or anything? just making sure =)

I guess this too of an in-depth thinking. Facilitated transport itself does not require ATP to transport Urea.

 

[Charles_Carmichael]

Yea, it's not active transport. The concentration in the collecting duct is much higher than it is in the interstitial fluid and urea travels from the collecting duct into the interstitial fluid in the presence of ADH. ATP is not required because there's no transport against the gradient.