Add labels to the figure that follows, which illustrates some molecules that can and cannot pass through cell membranes unaided.

Video transcript

Welcome back. Let's look at our next problem. It says which of the following best illustrates the molecules that can and cannot cross the cell membrane respectively. So that respectively means when we look at our answer choices, each one presents two types of molecules. So the first one should be something that can cross the cell membrane, and the second should be one that can't. And when we look at our illustration that we're given, we see um these small molecules composed of three atoms larger and two smaller crossing the cell membrane. That's pretty easy to identify as water molecules. And we know that water molecules are tiny enough that they can diffuse to the cell membrane. And over on the right we see sort of a large branched polymer that cannot cross through. So, let's look at our answer choices here. So we know that the first one, the one that is diffusing through these are water molecules. So we've got choice A is the only one with water as a first choice. The second molecule is carbohydrates. Well, this over here is a long branch chain polymer. Uh that is what a carbohydrate like. Starch looks like. So, I'm gonna go ahead and choose choice A. As describing our illustration here, when we look at our other choices, we for the choice of the can cross were given proteins, nucleic acids and lipids. Well, with proteins and nucleic acids, we have molecules that are too large or too polar to cross that phosphor lipid membrane lipids. Well, very tiny lipid molecules can sometimes diffuse through because of that. Um hydrophobic inner layer. But most lipids are just too large to cross through the cell membrane unaided. So Choice A. Is still the better choice and clearly shows that illustration of water. So Choice A water carbohydrates is our correct answer. The other answer choices being protein, being molecules that are too large or too polar to cross the cell membrane. Thanks for watching. See you in the next video.