Our example here tells us that shown below are two hormones interacting with a target cell. Based on the image, decide which side shows a steroid hormone and which side shows an amino acid-based hormone. Then it says to indicate what led you to make your decision. So we see a cell here, and we have it somewhat divided in two. We have a pink side on the left here and a purple side on the right. And we can see here on the left we have this molecule, which I'm assuming is the hormone in pink. It has an arrow coming up. It comes up to the cell membrane and it looks like it goes right through that cell membrane. It comes in contact with this green molecule and they seem to bind together where they then go in and bind to the DNA. Now, on the right, we have this purple molecule which, again, I'm assuming, is my hormone. It comes and it seems to bind to this receptor here, and that's sort of the end of the line for this purple molecule for that hormone. Now, inside the cell, all sorts of different stuff is happening. Messages and molecules seem to be tagging off, and eventually, something reaches and binds to the DNA, but the hormone seemed to stay outside the cell. Knowing that, I should be able to come up with my answer.
So, on the left here, for the pink molecule. Which type of hormone is able to pass through the cell membrane and bind to a receptor inside the cell? That's going to be a steroid hormone. And my reasoning? Well, I can just say that the receptor is inside the cell. Remember, steroid hormones are derived from cholesterol. They're lipid-based, so they can pass through the lipid bilayer of the cell membrane.
Now on our right here, we have this purple hormone. It is binding to the receptor, and then it doesn't go in the cell. So, what type of hormone can't cross the cell membrane and the receptors on the outside of the cell? Now that would be an amino acid-based hormone. And my reasoning? Well, the receptor is on the outside of the cell. The receptor is on the outside of the cell. And remember, amino acid-based hormones tend to be hydrophilic. They dissolve in water, which means that they cannot cross the lipid bilayer of the cell membrane, meaning the receptor has to be on the outside of the cell. Always remember these are general rules. There are exceptions to them. But that you definitely want to remember as a dividing point for those two types of hormones. More practice problems to follow. I'll see you there.
