Why does a Phospholipid have an unsaturated fatty acid tail?

  • Thread starter Hammad Shahid
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In summary, in the biochemistry chapter, the book shows a phospholipid structure with a PO4 3- group and 2 fatty acid chains attached to a glycerol molecule. One of the fatty acid chains has a C=C bond while the other is fully saturated, which is just an example to show important properties of such molecules. The variation in fatty acid chains affects the phospholipid's behavior as a fluid or stiff membrane, and also impacts its mechanical properties and transport capabilities.
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Hammad Shahid
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Homework Statement


Hi guys. In the biochemistry chapter, the book shows the structure of a phospholipid (picture attached) with a PO4 3- group and 2 fatty acid chains attached to a glycerol molecule. However, one of the fatty acid chains has a C=C bond while the other is fully saturated. I’m wondering what’s the reason for this.

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The Attempt at a Solution


I looked through the section and it doesn’t give an explanation for it. I also searched it up but I couldn’t find what I was looking for, and the images online had similar structures as well.
Thanks for help.
 

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  • #2
I doubt there is a "reason", looks like just an example made to show several important properties of such molecules.
 
  • #3
Borek said:
I doubt there is a "reason", looks like just an example made to show several important properties of such molecules.
Okay thank you. That is what I thought.
So that means there’s variation in the fatty acid chains? And does that affect the phospholipid in any way (if the chains are linear or not)?
 
  • #4
Yes and yes. cis-unsaturated fatty acids pack less efficiently than trans-unsaturated and saturated fatty acids. A higher proportion of cis-acids causes the phospholipid membrane to behave more as a fluid, whereas a higher proportion of saturated/trans-unsaturated acids acts to stiffen the phospholipid membrane. The balance of these affects the membrane's mechanical properties as well as the transport of various species across the membrane. Here's a relevant wiki page:
https://en.wikipedia.org/wiki/Lipid_bilayer_phase_behavior
 
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1. Why is a phospholipid's unsaturated fatty acid tail important?

The unsaturated fatty acid tail of a phospholipid is important because it allows for greater flexibility and fluidity in the cell membrane. This is because the double bonds in the unsaturated fatty acids create kinks in the tail, preventing the molecules from packing tightly together and making the membrane more fluid.

2. How does the unsaturated fatty acid tail affect the properties of a phospholipid?

The unsaturated fatty acid tail affects the properties of a phospholipid by making it more permeable to certain molecules. This is because the kinks in the tail create spaces between the molecules, allowing for smaller molecules to pass through more easily.

3. Can a phospholipid have more than one unsaturated fatty acid tail?

Yes, a phospholipid can have more than one unsaturated fatty acid tail. These molecules are known as polyunsaturated phospholipids and they have even more kinks in their tails, making them even more fluid and permeable.

4. How does the unsaturated fatty acid tail contribute to the stability of the cell membrane?

The unsaturated fatty acid tail contributes to the stability of the cell membrane by allowing it to remain fluid at a wider range of temperatures. This is because the kinks in the tail prevent the molecules from packing tightly together, making the membrane more resistant to freezing or melting at extreme temperatures.

5. Are there any negative effects of having an unsaturated fatty acid tail in a phospholipid?

There are no major negative effects of having an unsaturated fatty acid tail in a phospholipid. However, too many unsaturated fatty acids in the membrane can make it too fluid and unstable, potentially compromising the integrity of the cell.

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