Proteins question!

[panicatthelunchbar]

Hi guys, can someone please help me out here!?

I am confused between the functions of carrier and channel proteins. Which one of them plays a role in passive transport and which one in active transport and what do they help carry or transport across the cell membrane?

Any help would be great! Thanks!!

[WhoTookMyUsername]

*additional question - Do all carrier molecules require a channel protein?

[huaxiadragon]

Hi guys, can someone please help me out here!?

I am confused between the functions of carrier and channel proteins. Which one of them plays a role in passive transport and which one in active transport and what do they help carry or transport across the cell membrane?

Any help would be great! Thanks!!

I beliebe carriers are used for active transport and channel proteins are for passive transport.

It's been a while since I did bio but I think that's it

Passive transport should be used for the usual everyday glucose, smaller nutrients etc

Active transport is used to transfer relatively large or unusual stuff like a steroid or large chunch of nutrients

[Chromeo33]

Yeah I think you've been a bit confused with the various forms of diffusion.
This is what I've gathered so far this year:

Carrier-mediated (also called FACILITATED DIFFUSION):
Involves protein channels AND carrier molecules, no energy expenditure, from high conc. to low conc.

Channel-mediated:
Involves protein channels (NO CARRIER MOLECULES NEEDED), no energy expenditure, from high conc. to low conc.

Now any form of diffusion across a membrane THAT DOES NOT REQUIRE ENERGY is deemed PASSIVE transport, and so both channel- and carrier-mediated forms of transport are forms of PASSIVE TRANSPORT.

Active transport:
Involves protein channels (NO CARRIER MOLECULES), it DOES REQUIRE ENERGY EXPENDITURE, from low conc. to high conc.

All energy-requiring forms of diffusion are deemed ACTIVE forms of transport and so active transport is deemed an ACTIVE form of diffusion (as its name suggests!)

Hope that helped..

[dooodyo]

Hmm wouldn't active transport also be able to use
carrier molecules?  

[shinny]

As far as I'm aware, channels and carriers can do both. Wiki seems to agree with that. When they're acting passively, just think of channels as being analagous to human tetris (i.e. the 'doorway' fits one particular molecule and the molecule basically runs straight through it), while carrier proteins are kind of like revolving doors. If they're acting actively, a channel is basically like a door which opens after you press a button, while carrier proteins are kind of like those revolving garages that you see super rich people have so that they don't have to reverse their cars. You get inside first, press the button, and then the protein changes and spins around and lets you out the other side. I don't think the particular mechanism is very important anyway. I thought carriers and channels were basically the same thing during unit 3 and really there's not much application to it so it's almost impossible to be tested on.

[dooodyo]

Thanks heaps shinny that cleared things up