lipids

Question 1

Describe the structure of a fatty acid (RCOOH)

Answer 1

● Variable R-group - hydrocarbon chain (this may be saturated or unsaturated)
● -COOH = carboxyl group

Question 2

Describe how triglycerides form

Answer 2

● 1 glycerol molecule and 3 fatty acids
● 3 condensation reactions
● Removing 3 water molecules
● Forming 3 ester bonds

Question 3

Explain how the properties of triglycerides are related to their structure

Answer 3

● High ratio of C-H bonds to carbon atoms in hydrocarbon chain
○ So used in respiration to release more energy than the same mass of carbohydrates
● Hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets, tails inwards)
○ So no effect on water potential of cell (or can be used for waterproofing)

Question 4

Describe how the properties of
phospholipids relate to their structure

Answer 4

● Phosphate heads are hydrophilic
○ Attracted to water so point to water (aqueous environment) either side of membrane
● Fatty acid tails are hydrophobic
○ Repelled by water so point away from water / to interior of membrane

Question 5

Triglyceride condensation reaction in carboxyl and hydroxyl terms

Answer 5

*Reaction between hydroxyl groups in 1 glycerol and 3 carboxyl groups in 3 fatty acids.
*forming 3 ester bonds

Question 6

Compare and contrast the structure and properties of triglycerides and
phospholipids.

Answer 6

Both contain ester bonds (between glycerol and fatty acid);.
2. Both contain glycerol;
3. Fatty acids on both may be saturated or unsaturated;
4. Both are insoluble in water;
5. Both contain C, H and O but phospholipids also contain P;
Must relate to element.
6. Triglyceride has three fatty acids and phospholipid has two fatty acids plus
phosphate group;
7. Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic
and hydrophobic region;
Accept ‘non-polar’ for hydrophobic and ‘polar’ for hydrophilic.
8. Phospholipids form monolayer (on surface)/micelle/bilayer (in water) but
triglycerides don’t;