Phospholipids

Question 1

Describe the structure of a phospholipid?

Answer 1

• Same structure as triglycerides except one fatty acid molecule is replaced by a phosphate group
• Most phospholipids have an even number of carbons (16 or 18)
• Usually one fatty acid chain is saturated and the other unsaturated
• Soluble in water due to inorganic phosphate ions

Question 2

How does a phospholipid form?

Answer 2

Via a condensation reaction between an OH group on a phosphoric acid molecule and one of the 3 -OH groups on the glycerol
This forms an ester bond

Question 3

What are the functions of a phospholipid?

Answer 3

• Found in the cell membrane of all eukaryotes and prokaryotes to make up the phospholipid bilayer
• Cell membrane controls what enters and exits a cell. Phospholipid heads are hydrophilic but the fatty acid tails are hydrophobic. This forms a double layer with the heads facing outwards on either side of the membrane
• The middle of the membrane is hydrophobic - this means that water soluble substances can’t easily pass through it, so the membrane acts as a barrier