Facilitated diffusion across a membrane requires ______________ and moves a solute ______________ its concentration gradient.
a. transport proteins . . . up (against)
b. transport proteins . . . down
c. energy and transport proteins . . . up
d. energy and transport proteins . . . down

Question

Facilitated diffusion across a membrane requires ______________ and moves a solute ______________ its concentration gradient.

a. transport proteins . . . up (against)

b. transport proteins . . . down

c. energy and transport proteins . . . up

d. energy and transport proteins . . . down

Accepted Answer

Welcome back everyone here's our next problem. It says simple diffusion. In contrast to facilitated diffusion blank. Well, let's recall from our content videos distinction between simple and facilitated diffusion and it's kind of simple if we start with the very meaning of the word facilitated meaning with help. So facilitated diffusion is any kind of diffusion that requires some sort of aid to cross the cell membrane. Whether it's a membrane protein, it needs the input of energy or even need the pore in the membrane. So that's what facilitated diffusion is. So, simple diffusion is simply without help. So compounds that can diffuse through the cell membrane on their own without any sort of help and they're crossing um in a favorable direction with a concentration gradient. So from an area of higher to lower concentration which is what's responsible for that movement across the membrane. So with that in mind let's look at our answer choices. Choice A says needs the assistance of membrane proteins. Well, we can tell right there with the word assistance. That's not simple division that's facilitated diffusion which needs the assistance of membrane proteins. So we can eliminate that choice. B says move small non polar molecules. Well, this is correct because those are the only kind of molecules that can diffuse on their own through a cell membrane. They need to be non polar to be able to diffuse to those hydrophobic tales of the fossil lipids in the membrane and small to be able to fit through those rather tightly packed phosphor lipids. But we'll just look at our other answer choices to be thorough here, Choice C says, moves large polar molecules well, that would not be possible by simple diffusion. The polar molecules can't get through. They need the aid of membrane proteins, same with large molecules, which can't squeeze in there. They also need help to get in. And finally, Choice D. Says, uses energy to transport molecules well, again, that's a form of help that's facilitated diffusion. That's active transport when you're moving something against a concentration gradient or against an electrochemical gradient, and energy needs to be inputted to do that. So that's not simple diffusion. Obviously, so, Choice D. Is not our answer. So once again, simple diffusion, in contrast to facilitated diffusion, Choice B move smaller non polar molecules hope to see in the next video.

Facilitated diffusion across a membrane requires and moves a solute its concentration gradient.
a. transport proteins . . . up (against)
b. transport proteins . . . down
c. energy and transport proteins . . . up
d. energy and transport proteins . . . down

Verified video answer for a similar problem:

Key Concepts

Facilitated Diffusion

Concentration Gradient

Transport Proteins