1.3 Lipids

Question 1

What is the structure of a fatty acid?

Answer 1

• Carboxyl group
• Variable R group hydrocarbon chain

Question 2

What is the difference between saturated and unsaturated fatty acids?

Answer 2

Saturated have no C=C double bonds in hydrocarbon chain whereas unsaturated have at least one

Question 3

Triglycerides

Answer 3

Energy storage
1 glycerol molecule and 3 fatty acids joined by 3 ester bonds
High ratio of C-H bonds to C atoms so lots of energy stored, high ratio of H to O so act as metabolic water source, insoluble in water so don’t affect water potential by osmosis

Question 4

Phospholipids

Answer 4

Form bilayer in cell membrane, allowing diffusion of small lipid-soluble non-polar substances
1 glycerol molecule, 2 fatty acids and 1 phosphate group joined by ester bonds
Hydrophilic phosphate heads attracted to water, hydrophobic fatty acid tails repelled by water, insoluble in water so don’t affect water potential by osmosis

Question 5

How do you test for lipids?

Answer 5

• Add ethanol, shake then add water
• Milky white emulsion if positive