A cell may allow a large or charged chemical to move across th...

Question

A cell may allow a large or charged chemical to move across the cytoplasmic membrane, down the chemical’s electrical and chemical gradients, in a process called _________ . .

a. active transport

b. facilitated diffusion

c. endocytosis

d. pinocytosis

Accepted Answer

Hello everyone. The next problem says the mechanism that uses a TP energy to pump ions against a chemical gradient via transmembrane protein channels is known as a simple diffusion. B osmosis C active transport or D facilitated diffusion. Well, when we think about things moving across a semi permeable membrane, we kind of think about two aspects of this one. Are they moving down an electrical chemical electrochemical gradient or up an electrochemical gradient? So with it or against it, in this case, we know they're moving it against it. In that case, they will need some sort of energy input to push them essentially uphill. And then the other part is, are they doing this with or without the help of some sort of protein? Are the molecules moving through the membrane by themselves? Because they're very small or nonpolar or are they large and polar and need some sort of protein channel to move through? Well, we know we have transmembrane protein channels. So our two types of transport that involve help from protein channels are choice c active transport and choice C facilitated diffusion. So then we look at are we going against the gradient or with it. Well, choice c active transport is the one that uses protein channels and works against the gradient. And its very name can help you remember this because just as you would have to do active work to push a boulder up a hill as opposed to just tipping it so that it'll roll downward. If we're moving proteins against their electrical chemical gradient, we're having to do active work to make them move in that direction, facilitated diffusion. On the other hand, we have help from protein channels. So in this case, our question is asking about ions, we have ions, they're charged, they can't move through a nonpolar membrane on their own. But our ions are moving down an electrical chemical gradient. In the case of facilitated fusion, they have helped to get through, but they're moving the way they naturally want to move. So that's why Twisty is not our correct answer. So I say simple diffusion is both, we've got diffusion, they're both moving down the electrical chemical electrochemical gradient. And that simple diffusion means there here we're talking about particles that can move through on their own. So it wouldn't actually be an electrochemical gradient because charged particles won't move through a membrane on their own. But perhaps they're just very small molecules. So they can work their way through those livid molecules of a membrane and its diffusion, they would be moving down in this case, a concentration gradient. So in the direction they want to go anyway, but obviously not the right description of what's going on here. And then finally, choice B osmosis, this is not the movement of particles but the movement of water across a semi permeable membrane. And sometimes it's a little tricky to keep straight what direction this is going. But in this case, the water is going to move from an area of low solute concentration to an area of high solute concentration. And the way we remember this and keep track of which direction things would move. As we remember, things will always move naturally in the direction to equalize the concentrations on both sides. So if the particles are moving, they will move from an area of high concentration to low concentration. If the water is moving, it's essentially going to be trying to dilute the side with the higher solute concentration. So it move from an area of lower solute concentration to an area of higher solute concentration. So some of you always have to stop and check and think what's moving and how am I going to move in the direction that equalizes the concentrations or goes in the direction of that. But osmosis is not what we're talking about. So it's not our answer. So once again, the mechanism here that uses a TP energy to pump ions against an electrochemical gradient via transmembrane protein channels is known as choice c active transport. See you in the next video

A cell may allow a large or charged chemical to move across the cytoplasmic membrane, down the chemical’s electrical and chemical gradients, in a process called _________ . .

a. active transport
b. facilitated diffusion
c. endocytosis
d. pinocytosis

Key Concepts

Facilitated Diffusion

Chemical and Electrical Gradients

Passive vs. Active Transport

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