Phospholipid Structure

Phospholipid Structure

Our phospholipid is typically represented as having a polar phosphate head group and two fatty acid chains, all held together by a glycerol backbone.

⛓ Fatty Acids

Each phospholipid contains two fatty acids. A fatty acid consists of a carboxylic acid attached to a long carbon chain (R-group). A carboxylic acid has a double-bonded oxygen and a hydroxyl group ($COOH$).

🧰 Glycerol Backbone

Each phospholipid has only one glycerol molecule. Glycerol has a simple structure consisting of three carbons, each attached to a hydroxyl group ($OH$).

💡 Phosphate Group

The phosphate group is the polar head of the phospholipid. It consists of a phosphorus atom with four oxygens attached to it.

🧩 Putting it all Together

The two fatty acid chains attach to the glycerol backbone through ester bonds. The glycerol then attaches to the phosphate group through another ester bond. One of the oxygens in the phosphate group is replaced by a hydroxyl group ($OH$) in the cell.

🧬 Phospholipid Diversity

Phospholipids can bond with several different molecules, which allows for a diverse set of phospholipids. These molecules include serine, choline, ethanolamine, inositol, and glycerol. The hydroxyl groups ($OH$) on these molecules can bond to the phosphate group through a phosphoester bond.

📃 Common Phospholipids

There are five common phospholipids:

• Phosphatidylserine

• Phosphatidylcholine

• Phosphatidylethanolamine

• Phosphatidylinositol

• Diphosphatidylglycerol (cardiolipin, which has two phosphatidyl groups bonded to a central glycerol)

The phospholipids in our cell membrane are very diverse, and there are several different forms they can take.

polar vs nonpolar

• The polar head group faces the outside.

• The nonpolar fatty acid chains face the inside.

• The glycerol group holds everything together.

↔ Cis and Trans Bonds

The carbon chains in the fatty acids can form double bonds. These double bonds can be in the cis or trans form.

• Cis Bond:

• Trans Bond:

The presence of cis bonds and trans bonds affects the fluidity of the cell membrane.

🔑 Summary

Phospholipids consist of fatty acids, glycerol, and a phosphate group. The phosphate group can bond with other molecules, creating a diverse array of phospholipids in the cell membrane.