Phsopholipids formation - phosphate group and the glycerol bonding

Practice Question Solving
1

I recognize the bond between the phosphate group and the glycerol is an ether bond, but how is the bond made? does the glycerol release a proton to the environment and then contently bonds to the oxygen atom? I guess there’s no condensation reaction.
thanks

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2

The process of forming a bond between a phosphate group and glycerol, as seen in the formation of a phospholipid molecule, is a condensation reaction. The reaction is referred to as “condensation” because a small molecule, in this case water, is released or “condenses out” during the process.

The hydroxyl (-OH) group on the phosphate reacts with a hydrogen atom from the hydroxyl group on the glycerol, creating water (H2O) and leaving behind a bond between the oxygen from the phosphate group and the carbon of the glycerol.

You are correct that this new bond is an ether bond, but it’s also known as an ester bond in this context. In the specific case of a phosphoester bond (the bond between the phosphate group and the glycerol), it’s an oxygen atom from the phosphate group that forms the bond with a carbon atom of the glycerol.

Here is a simplified version of the reaction:

Glycerol -OH + H-O-Phosphate → Glycerol-O-Phosphate + H2O

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Great! so the initial phosphate molecule is actually hydrogen phosphate right?

4

Yes, hydrogen phosphate = phosphate ion.

5

There are actually several forms of phosphate ions that can exist at different pH values. The most common ones are the phosphate ion (PO4^3-), the hydrogen phosphate ion (HPO4^2-), and the dihydrogen phosphate ion (H2PO4^-).

These phosphate ions are acidic, meaning they can donate protons (H+ ions) to a solution. This is why they have hydrogens attached.

When a phosphate ion is bonded to a molecule such as glycerol, it’s usually one of the hydrogen phosphate ions (HPO4^2- or H2PO4^-) that participates in the reaction, because these forms have hydrogens that can be removed in the condensation reaction to form water.

But in a biological context, these reactions are usually mediated by ATP (Adenosine Triphosphate), which has three phosphate groups, and the terminal phosphate group is transferred to the glycerol during the formation of a phospholipid. The enzymes responsible for this type of reaction are known as phosphotransferases.

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