Types of Small Molecule Transport Review

in this video, we're going to do a review of the different types of small molecule transport that we already talked about in our previous lesson videos. And so because this video is a review, there is not really going to be any new information provided in this video that we didn't already cover. So if you're feeling pretty good about this already, then you can feel free to skip this video if you'd like. However, if you're looking for some additional support, then stick around for this review. And so notice that down below in this image, we have some of these different types of transport that we covered in our previous lesson videos. And so notice that on the far left we have simple diffusion which is a type of passive transport, meaning that no energy is required and the molecules will be transported down their concentration gradient from an area of high concentration to an area of low concentration. And so, simple diffusion as its name implies, is pretty simple because the molecules are able to simply diffuse right through the membrane without any facilitation whatsoever. From an area of high concentration down to an area of low concentration across the membrane notice that no protein facilitators needed and these molecules are able to simply diffuse right between the fossil lipids and so they need to they tend to be really, really small molecules that are non polar. Those are the ones that have the best chance of being able to diffuse across the membrane without any facilitation. Then over here, what we have is facilitated diffusion, which is another type of passive transport. Once again passive transport, meaning that there's no energy input needed and the molecules are going to be transported from an area of high concentration to an area of low concentration across the membrane. Now notice that these molecules here are ions, they are charged. They have these little plus symbols inside of them representing that they're positively charged and ions they have a difficult time crossing the membrane without any facilitation. So these ions cannot defuse via simple diffusion. Instead, they require facilitation from a membrane protein, like a channel, for example. And so this channel will allow this ion to diffuse across the membrane from an area of high concentration to an area of low concentration, but no energy input is needed. Yeah. Now, active transport, on the other hand, does require the input of energy to transport molecules against their concentration gradient from an area of low concentration to an area of high concentration across the membrane. And so primary active transport recall is going to utilize a teepee directly in order to power a uh the movement of a molecule across the membrane once again against its concentration gradient from an area of low concentration to an area of high concentration. And so because http is being utilized directly, that makes it primary active transport now, secondary active transport does not directly use A. T. P. Instead it indirectly uses A. T. P. And it directly uses the concentration gradient of another molecule to power active transport. And so notice that as this pink molecule is being transported down its concentration graded from high to low, it will release energy in an extra chronic process to power this other molecule and green against its concentration gradient from low to high. And so this low to high. Here is the active transport part because it's going against its concentration gradient and it's being powered by this uh pink molecule going from high to low. And then last but not least we have over here is group translocation which is mainly specific to bacteria. And this will chemically modify the entering molecule as it enters into the cell. And the example that we talked about previously is glucose being chemically modified to glucose six phosphate as it enters into E. Coli bacteria. And so it does require the high energy molecule as well, too chemically modify the entering molecule. And so sometimes you'll see group translocation grouped as some alternative type of active transport. But here this concludes our review of these different types of small molecule transport, and we'll be able to get some more practice as we move forward. So I'll see you all in our next video.

Which of the following transport mechanisms require energy?

• A. Active transport.
• B. Facilitated diffusion.
• C. Passive diffusion.
• D. a&b.
• E. None of the above.

Which of the following processes requires a carrier protein?

• A. Diffusion.
• B. Facilitated diffusion.
• C. Active transport.
• D. Endocytosis.
• E. b&c.

Which of the following types of membrane transport modifies a chemical as it is transported into the cell?

• A. Facilitated Diffusion.
• B. Simple Diffusion.
• C. Modified Transport.
• D. Group Translocation.
• E. Secondary Active Transport.