Question About Diffusion vs Secondary Active Transport

[BMW M3]

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Sodium flux during an action potential is an example of what transport mechanism:

A) Carrier Mediated Diffusion
B) Paracellular
C) Primary Active Transport
D) Secondary Active Transport
E) Diffusion


Is this a valid question that we can expect on Step 1?
Kaplan says E
I say A because its a sodium channel protein
My friend says D because the sodium gradient was created by the Na/K ATPase pump

Thanks

 

[MedLover25]

I would agree with you and say A as well.

You're friend gave you correct information, but I don't believe that answers the question.

 

[Mediculous]

It's facilitated diffusion. The reason it's not carrier-mediated(which is a type of facilitated diffusion) is because, like you said, Na+ is brought in through an ion-channel(the other type of facilitated diffusion). The bigger molecules, like glucose and amino acids can use carrier-mediated diffusion, along with other types of transport. It's not secondary active transport because that involves the transport of something against its concentration gradient along with the transport of something down its gradient(at the same time). Secondary transport uses either a co-transporter or anti-transporter. The answer choice being just "diffusion" is vague but correct.

 

[BMW M3]

It's facilitated diffusion. The reason it's not carrier-mediated(which is a type of facilitated diffusion) is because, like you said, Na+ is brought in through an ion-channel(the other type of facilitated diffusion). The bigger molecules, like glucose and amino acids can use carrier-mediated diffusion, along with other types of transport. It's not secondary active transport because that involves the transport of something against its concentration gradient along with the transport of something down its gradient(at the same time). Secondary transport uses either a co-transporter or anti-transporter. The answer choice being just "diffusion" is vague but correct.

thanks!

 

[RussianJoo]

yep I would go with kaplan on this and also say it's diffusion. Na+ travels down it's concentration gradient through a channel. If the gradient didn't exist then Na wouldn't move into the cell. It's not carrier mediated because there is no carrier it's just a channel or a hole that opens in the membrane, and it's not an active transport because Na is moving down it's concentration gradient not up the gradient.


and yes this can easily be a USMLE question. and would be a pretty good one in fact.

 

[obiwan]

whats a good source for this type of content? FA doesn't really have material along these lines...

 

[SOUNDMAN]

whats a good source for this type of content? FA doesn't really have material along these lines...

BRS Physiology, first chapter?

 

[RussianJoo]

BRS Physiology, first chapter?

yep this is basic physio and can be found in any introductory chapter.