moving on to membrane structure. If you haven't done question 22 yet, pause the video now. All right, so the fossil light based that is most likely Thio remove an unsaturated fatty acid from fossil lipid is possible light based too. And the reason for this is well, first, let's just draw our Foss Philip ID. Right? So here we have our phosphate group and this is attached to the head. Right? And here we have our Esther Bond. You know, this is whatever on Dhere, we have another Esther bond and whatever fatty acid is there. Okay, So what? I was, uh, kind of like what we were just looking at before. Here's the one position Thio. And three, it's the heads on the three fatty acids. Aaron 12 And if, um, if there is on Lee one unsaturated fatty acid like we were just saying, it's always gonna be at two position, and that's where possible. Light base a two cuts. It cuts right here. A one cuts up here and see cuts right here. And D cuts right there so you can see that a two would be the most likely to remove an unsaturated fatty acid because most well, if there's only one unsaturated fatty acid, it's going to appear the two position and that's a two is cutting there. Great. So the shortest helix segment that could span a membrane is about 20 amino acids long. This is just a fact. Um, not much else to say about this. Five isn't long enough. 50 could certainly do the job. 102 100. Probably getting a little a little excessive there. Right. So an integral membrane protein can be extracted with a solution containing detergent. And the reason for this is integral. Membrane proteins have hydrophobic and hydro filic regions. Right? They're gonna have thes hydro filic regions in the head area or in the head and tail. That's sort of how I think of it anyways. And then this hydrophobic membrane spanning region, right? So I've drawn the hydrophobic region and read the hydro filic regions in blue. And you need to use detergent because you need the detergent molecules to interact with the hydrophobic portion of the the hydrophobic portion of the protein. And so they're detergent molecules. They have hydrophobic tails. They actually have hydro filic heads. So I should actually draw these in blue to be consistent, right? Let me change those two blue. All right, So those are the hydro, uh, red squiggles or like the hydrophobic tails, the blue dots or the hydro filic heads. And so the detergent molecules will help extract the integral membrane protein by sort of, you know, stabilizing that hydrophobic portion, which is normally embedded in the membrane. But now you want to remove it from the membrane, so you have to do it like this. Looking at Question 25 which of the following are not enzymes involved in moving fossil obits from one leaflet to another that's like from one side of the membrane to the other? The answer is C flip flop paces. That's not a real thing. You have flip bases, flop bases and scramble aces. So if we sort of pretend this here is our membrane and here is the inside and here is the outside. You have flip bases that move something from the outer leaflet to the inner leaflet. That's a flip. Ah, flop is the opposite direction. Right Flop brings something from the inner leaflet, or you could call it the site. Is Olic leaflet because the inside is going to be. The site is Olic side, as opposed to the outside being the extra cellular fluid, the external fluid. So I a flop pace will move something from the inside the outside and scramble ace does the flip flop right? It scramble is, is kind of like the flip flop pace, but it's of course, called scramble ease. All right, so last questions take a look. A 26 year. The plasma membrane of animal cells contains 45% by weight, fost Philip ID and 55% of protein. What is the mole ratio of lipid to protein? Assuming the average molecular weight of Fost Philip, it is 750 Dalton's and the average molecular weight of membrane proteins is 60 1000 Daltons. Alright, so basically the easiest way to answer this question you're giving these percentages. Let's just pretend that you have 100 total grams of you know your membrane. So that would mean that you'd have 45 g of possible lipid and you would have g of protein and you'd want to divide those by those Wait. So 750 Dalton's And here we have 60,000 Dalton's, and that's going to give you your answer. In moles, you have six moles lipid and 9.2 times 10 to the negative fourth moles of protein, and you want to find the ratio of lipid to protein so you're going to divide lipid by protein. So divide these two numbers and what you get is about 65 approximately, uh, All right, let's flip the page.