1. Biological Molecules - Lipids

Question 1

Name 4 features of all lipids:

Answer 1

-Contain C, H, O
-Proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
-Insoluble in water
-Soluble in organic solvents such as alcohols

Question 2

What are the 5 main roles of lipids?

Answer 2

-Cell membranes
-Source of energy
-Waterproofing
-Insulation
-Protection

Question 3

What do phospholipids contribute to cell membranes?

Answer 3

They contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them.

Question 4

Compare the amount of energy in lipids to carbohydrates:

Answer 4

When oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water.

Question 5

How do lipids help waterproofing in plants and insects?

Answer 5

Both plants and insects have waxy lipid cuticles that conserve water.

Question 6

How do lipids help waterproofing in mammals?

Answer 6

They produce an oily secretion from sebaceous glands in the skin.

Question 7

In which two ways do lipids help with insulation?

Answer 7

Both thermally and electrically (in myelin sheath around nerve cells).

Question 8

What are triglycerides?

Answer 8

Three fatty acids combined with a glycerol molecule.

Question 9

What kind of reaction is used to join the glycerol molecule with the fatty acids?

Answer 9

A condensation reaction.