Lipids

Question 1

Describe the structure of a triglyceride.

Answer 1

1 glycerol molecule joined to 3 fatty acid tails by ester bonds.

Question 2

Describe the structure of a phospholipid.

Answer 2

1 glycerol molecule joined to 2 fatty acid tails and a phosphate group.

Question 3

Describe the structure of a cholesterol.

Answer 3

It is a molecule made up of 4 carbon rings.

Question 4

What type of triglyceride is commonly found in plants?

Answer 4

Unsaturated (oils)

Question 5

What type of triglyceride is found in animals?

Answer 5

Saturated (fats / waxes)

Question 6

Give the properties and functions of triglycerides.

Answer 6

Compact energy store.
Insoluble in water.
Does not affect cell water potential.
Stored as fat providing insulation and protection.
Provides buoyancy.
Provides waterproofing (on feathers, leaves).
Source of water (from respiration – camel’s humps).
Provides electrical insulation around neurons .
Helps in the absorption of fat soluble / A / D / E / K, vitamins.

Question 7

Give the properties and functions of phospholipids.

Answer 7

Hydrophilic head and hydrophobic tail, so ideal basis for cell surface membranes.
Phosphate may have a carbohydrate attached forming glycolipids involved in cell signalling.

Question 8

Give the properties and functions of cholesterols.

Answer 8

Small, hydrophobic molecules that can fit into the lipid bilayer giving strength and stability.
Used to form steroid hormones.

Question 9

What is the test to identify the presence of a lipid?

Answer 9

The emulsion test;
Mix with ethanol,
Pour into water,
If a white emulsion forms, a lipid is present.