Everyone, in this video, we're going to take a look at phosphoglycerides. With phosphoglycerides, we can say they belong to a class called phospholipids. These are just lipids that contain a phosphate group attached to a Glycerol or Sphingosine backbone. Like fatty acids, phospholipids are amphipathic, meaning they contain portions that are polar and nonpolar. They have a hydrophilic head and a hydrophobic tail. If we take a look at our phospholipid, it is better depicted in terms of the bonds involved. For a simpler view, we have our hydrophobic head here and our hydrophobic tail. These can organize themselves to help create what we call a lipid bilayer. Remember, when we talk about lipids, we break them down into hydrolyzable and non-hydrolyzable categories. Our phospholipids belong to the hydrolyzable portion, which includes Glycerol Lipids and Sphingolipids. The portion we are concerned with is our Phospholipids which contain Phosphoglycerides and Sphingomyelins. Looking at the key differences, with Phosphoglycerides, we have Glycerol as our backbone, two fatty acid chains, and a phosphate group connected to an amino alcohol. With sphingomyelin, the backbone is Sphingosine. We still have a fatty acid, and we have our phosphate with Amino Alcohol. In addition to this, phospholipids are a major component of all cell membranes, and the rigidity of the lipid bilayer depends on the identity of the fatty acids that compose the phospholipids. They are an incredibly important category of lipids because they are components of all cell membranes that we talk about in biological systems. Keep in mind some of these key points when it comes to our phospholipids.
Phosphoglycerides - Online Tutor, Practice Problems & Exam Prep
Phosphoglycerides Concept 1
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Phosphoglycerides Example 1
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Which one of the following is not a component of phospholipids?
So we did talk about phospholipids being involved with fatty acids because it is underneath the umbrella term of fatty acids. Phosphate. We said that phospholipids, an important aspect of them, is that they contain a phosphate group. It can be connected to a glycerol molecule or a sphingosine molecule. Cholesterol. Cholesterol here is not a component of phospholipids, and in fact, it belongs under the category of steroids. So here, this would be our answer. Then finally, Glycerol. Glycerol can be a vital component of phospholipids. It forms a potential backbone in terms of the attachment of the phosphate group. So this would also be a component of phospholipids. So here the only answer that's correct is option c. Cholesterol is not a component of phospholipids.
Phosphoglycerides Concept 2
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In this video, we talk about our phosphoglycerides. Now we're going to say here that our phosphoglycerides, also called our Glycerophospholipids, are phospholipids with a Glycerol backbone and 2 fatty acids. Now, here we're going to say again they're composed of a head and a tail region. The head is a phosphate group extended with an Amino Alcohol head group, and the tails, there are 2 fatty acids attached through Ester Bonds. Now, here we're going to say they are classified based on the Head Group Attached to the Phosphate Group. If we take a look here at our types of Phosphoglycerides, we have our two classes, which are our Sphingolipids and our Lecithin. Here, the differences come with the different types of head groups involved.
With Cephalin, the head group is an Ethanolamine. And here Nitrogen is making 4 bonds, so it is positively charged, Its groups would be Hydrogens. An example of this would be this structure. We can see the head group here, our Ethanolamine. We have our phosphate group. We have our glycerol backbone in blue. And then, notice that we have 2 fatty acids. They could be saturated or unsaturated. They could be the same. They could be different. Now, here with Lecithin, its head group is different. Here, its head group is Choline. Notice that here, instead of having hydrogens attached to nitrogens, we have methyl groups and there are 3 of them. Here we have our head group, our phosphate group, we have our glycerol backbone, and our 2 fatty acids. Again, they could be saturated or unsaturated; that's not important here. The defining characteristics of these two classes are in the types of head groups attached.
Now, here finally we can say that phosphoglycerides again are the most abundant lipids in all cell membranes. Remember, they help to make the lipid bilayer. That's why they're found in so many I mean, all cell membranes, right. So just keep this in mind when we're talking about our phosphoglycerides; we have 2 classes. Those classes depend on the type of head group attached.
Phosphoglycerides Example 2
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This example question asks, what is the basis of the classification of Glycerophospholipids? Now remember, we said that it is the type of head group that's attached to our phosphate that determines the classification for Glycerophospholipids. So we take a look here, it's not about the fatty acid molecule of carbon 1, the number of double bonds in the carbon 2 fatty acid, or the fatty acid molecule of carbon 2. Again, it is the head group that's attached to the phosphate group. And remember, here we can have either an Ethanolamine Group as the Head Group or a Choline as the Head Group. In both cases, we have a Nitrogen making 4 bonds and therefore it's positively charged. With an Ethanolamine head group, we have Nitrogen connected to 3 Hydrogens, an Ethyl group then connected to an Alcohol. And then for Choline, the Nitrogen is not connected to Hydrogens but to 3 methyl groups and it still possesses a positive charge. So in this particular question, it's the head group attached to the phosphate group that deals with the classification of our Glycerophospholipids.
Which one of the following statements accurately describes the difference between cephalins and lecithins?
Cephalins contain saturated fatty acids while lecithins have unsaturated fatty acids.
Lecithins and cephalins have different backbone molecules.
The head groups in cephalins and lecithins are ethanolamine and choline, respectively.
Lecithins do not have a head group.
Phosphoglycerides Concept 3
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Now, when it comes to drawing Glycerophospholipids, we're going to say it requires recalling the structures of the fatty acids and head groups. Alright. So, here it says draw the structure of a Glycerophospholipid that contains 2 lauric acid Acetyl groups and ethanolamine bonded to the phosphate group. Alright. So, here, the way we're going to approach this is step 1, we're going to draw the Glycerol backbone with the phosphate group at carbon number 3. So remember, we're going to say this is 1,2,3, we're going to say instead of 2 OH groups at carbon 1 and 2, we're going to write only oxygen atoms. So here, carbon 1 and 2 we have an oxygen here and an oxygen here, we already have our Phosphate group connected to Carbon 3. Next, we're going to say step 2, extend the Phosphate group at Carbon 3 with CH2CH2 group and Ethyl group. And we're going to say we're going to complete the head group with a NH3+ group because it's ethanolamine, or we're going to complete it with a nitrogen connected to 3 methyl groups, and it's also positive if it's a choline group. So here we're going to say we have CH2, CH2 attached. They told us it's an ethanolamine, so it's going to be an NH3+ group attached. And then let's see. So then we're done with that portion. And then finally, it says draw the 2 fatty acyl groups. So here we're going to say, remember, we don't include the OH group of the fatty acid from the 2 oxygen atoms at carbons 1 and 2. Alright. So we have our ethanolamine group attached, and they're telling us within this question it's 2 lauric acid Acetyl groups. Remember, lauric acid is going to be a saturated fatty acid. It has 12 carbons in total, and it has no pi bonds. So we just have to draw that out. So 2, 4, 6, 8, 10, 12. Same thing here. 2, 4, 6, 8, 10, 12. So here, this would be the structure of our Glycerophospholipid based on the description at the beginning of the example question.
Draw a glycerophospholipid with lauric acid at C1, myristic acid at C2, and choline bonded to phosphate.
Draw a cephalin with stearic acid at C1 and oleic acid at C2.
Phosphoglycerides can undergo saponification reaction. Draw products of complete basic hydrolysis of following cephalin. (Hint: 5 products are formed.)