1.5 lipids

Question 1

list the 5 roles of lipids.

Answer 1

• cell membranes: around the cell & organelles & phospholipid
• energy: release by oxidation & releasing water
• waterproof: cuticles for plants (reduce water loss from transpiration) & oils from sebaceous glands in animals
• thermal & electrical insulator: layer under skin / myelin sheath around nerves
• protection: delicate organs (eg. kidney & heart)

Question 2

how are triglycerides formed?

Answer 2

condensation reaction with ester bonds by 3 fatty acids & 1 glycerol

Question 3

what is the test for lipids?

Answer 3

emulsion test:
- dissolve in ethanol then water
- if a cloudy emulsion forms, lipids are present

Question 4

in what ways could fatty acids be different from each other?

Answer 4

• carbon chain length
• degree of saturation

Question 5

what are the 4 uses of triglycerides?

Answer 5

• great energy source: high C-H ratio
• energy storage: low mass:energy ratio
• doesn’t affect water potential: large, insoluble & non-polar
• source of H2O when oxidised

Question 6

describe the nature of the phospholipid head & tail.

Answer 6

hydrophillic phosphate head & hydrophobic fatty acid tail

Question 7

how are glycolipids formed?

Answer 7

phosphate head attaching to carbohydrates

Question 8

how are phospholipids formed?

Answer 8

phosphate group + glycerol + 2 fatty acids