Hello everyone and welcome to Big Orange Biology, I am Mr. Ginnings and today we're going to be talking about lipids. Now lipids are hydrocarbons composed of carbon and hydrogen atoms that are insoluble in water. That's because the bonds between carbon and hydrogen are extremely non-polar. Most hydrocarbons in general are non-polar compounds. Great examples of hydrocarbons besides lipids be things like plastics which are derived from oils. When close together these lipids are weak but have an additive property known as Van der Waals interactions hold them together. That's due to the uneven distribution of electrons on those atoms. So it's a force that when you put into play here so say you got yourself some lipids, get ourselves a phospholipids here. The Van der Waals force is going to kind of keep these lipids together and that plays a very key role in lipid structure. Now lipids themselves primary function is the store energy, specifically in the bonds between the two between carbon and the carbon hydrogen bonds. Now lipids can also play a very big structural role in cell membranes. These are our phospholipids as I mentioned a second ago and they can also provide structural overall adaptation support as an effect in animal bodies for thermal insulation. Now the chemical storage property most of us are familiar with lipids being as a primary energy storage molecule. That's what is taught generally in general biology but in real world AP we need to understand that does play a very valuable for cell membranes and addition to its energy functions. Now your typical energy based lipids are known as your triglycerides. These are the lipids that you probably think about when you hear the words lipid. These are commonly are the fats and oils. Triglycerides are very very little polarity. There is a little bit of a polar region at the top but not a strong one but they're in general they are extremely hydrophobic. So if I put a yet triglyceride into a aqueous solution or water-based solution it will separate as fast as it can from water and any other polar molecules that might be present. Now triglycerides are made of structurally speaking three fatty acids. Now fatty acids are non-polar hydrocarbons that have a carbolacyl acetylic acid group on the end. That kind of gives it the light polar region. That's a big thing here. The carbolacyl group is a polar group so slightly polar region at the top with your oral the fatty acids are non-polar. As we see here you have triglyceride which is an alcohol a very common alcohol and three fatty acids and the OHs and Hs will basically split off to make water. Now structurally speaking fatty acids can vary in length and structure. The longer they are typically speaking the more energy they have. Now saturated fatty acids structurally speaking have the most hydrogens attached to them. Hence the word saturated they are full of hydrogen because they're a full hydrogen they are very rigid using the term there to describe molecule basically they cannot bend if everyone is a little dashes here off the C was to represent a hydrogen there's not a lot of room for carbon to bid. Now unsaturated fatty acids are hydrocarbons that have a double bond here and there so when you have a double bond on a carbon because carbon can only bond four times, conveniently speaking that means for instance this carbon here can only bond two times in addition to its double bond. In this carbon can only bond one time in addition to its double bond and it's linked to the other carbon. This creates the situation where there's less resistance and space being taken up by hydrogen. A hydrogen is a very small atom it does take a broom and without the hydrogen there that allows this molecule to form kinks and be easily packed together tightly. Now unsaturated fatty acids are loose they actually have very little melting points because it doesn't take much energy to get them moving some more and it's such their typical uralicwix. Here's a great example when we're talking about that look in the space filling model a hydrogen's arm every single carbon. There is literally no room for this thing to move if it was ingested it will stay in this rigid form pretty much the entirety of its time until it's digested properly. You won't compare it to a linoic acid here. linoic acid has these double bonds located because of those double bonds there's less hydrogen in the space filling model. I mean this thing can take possibilities of different forbs because the double bond allows a carbon to kind of get some folding going so it can fold in multiple directions. It creates this distinct l shape versus the linear line shape that's all because the lack of hydrogen right there in the middle. Hydrogen is not taking up space there's no electron repulsion going on it's allowed it to flow a little bit better. Now fatty acids in general amphipathic as I mentioned before has a solid hydrophobic and a hydrophilic in. Now fossil lipids take advantage of this amphipathic method and take it to another level because fossil lipids instead being three fatty acids are two with a phosphate group taking the place of the third fatty acid when it binds to the glycerol. Now the phosphate group because it is a negative charge it makes that part of the molecule even more hydrophilic so it pretty it takes a while to absorb it and makes it more pronounced. So the phosphate over here phosphate got an slightly negative charge is a polyatomic ion a very common polyatomic ion and this is what we usually wear with a present with a solid head with two tails. This is your traditional phospholipid this molecule here plays a key role in cell biology. This molecule is the literal boundary for your cell. Without this molecule certain molecules could travel through the cell membrane and now it costs a lot of difficulties for homeostasis. When you put fossil lipids in a water environment it will form a bilayer naturally. Numpolar hydrophobic tails will point inwards in the hydrophilic heads will face outwards and because of this all biological membranes as far as we know are fossil lipid bilayer. They may have different varieties of phospholipids with different functional groups and such attached but in general the basic structure is still there and is what we call a highly conserved trait in biology if we say something's highly conserved it means it's evolutionary been official to be like that. So on the outside here you have a polar region on the outside and the inside but in the middle you have a big old nonpolar region. What that's going to do is this makes it going to be very difficult for polar molecules to pass through and it's really going to be more of something we're going to explore in the future and then next couple units. But however you need to be able to hear that fossil lipid bilayers are much more complicated than what we're seeing here in this picture. This is a simplistic rendering of the phospholipid bilayer. In conclusion lipids are more than just energy storage molecules. They are more than just fats and oils. A good number of lipids form the lipids in your cell membranes. Without you would have trouble difficult you would have difficulty functioning. So in the end of the day lipids are just these big long chains of hydrocarbons which don't interact with water but because that lack of interaction with water makes it a strong contender for a structural molecule that is necessary to deal with the harshness that is water that is universal solvacy. Now that will conclude today's video. Next time we'll be talking about proteins and polypeptides in general. Alright thank you for watching. This has been a big orange biology. Have a great day.