1.3

Question 1

Name, two groups of lipid

Answer 1

Triglycerides and phospholipids

Question 2

How are triglycerides formed?

Answer 2

by the condensation of one molecule of glycerol and three molecules of fatty acid.

Question 3

What does a condensation reaction between glycerol and a fatty acid (RCOOH) form?

Answer 3

An ester bond

Question 4

The R-group of a fatty acid may be ….

Answer 4

Saturated or unsaturated

Question 5

In phospholipids, one of the fatty acids of a triglyceride is substituted by …..

Answer 5

a phosphate-containing group.

Question 6

Describe how to test for lipids in a sample

Answer 6

1. Dissolve solid samples in ethanol.
2. Add an equal volume of water and shake.
3. Positive result: milky white emulsion forms

Question 7

Relate the structure of triglycerides to their function

Answer 7

– High energy: mass ratio = high calorific value from oxidation (energy storage)
– Insoluble hydrocarbon chain = no effect on water, potential of cells and used for waterproofing
-Slow conductor of heat= thermal insulation, E.G.adipose tissue.
-Less dense than water= buoyancy of aquatic animals

Question 8

Describe the structure and functions of phospholipids

Answer 8

Glycerol backbone attached to hydrophobic fatty acid tails, and one hydrophilic polar phosphate head
– Forms phospholipid bilayer in water = component of membranes
– Tails can splay outwards= waterproofing

Question 9

Compare saturated and unsaturated fatty

Answer 9

Saturated:
– contain only single bonds.
– straight-chain molecules have many contact points.
– Higher melting point = solid at room temperature.
– found in animal fats.

Unsaturated:
– contain C=C double bonds
– Kinked molecules have fewer Contacts points
– Lower melting point = liquid at room temperature
– Found in plant oils