Lipids - Mark Scheme Answers (study Mind)

Question 1

What is an unsaturated fatty acid? (2m)

Answer 1

Double bond(s) between carbon;

Question 2

Describe how you could use the emulsion test to show that a seed contains lipids.

Answer 2

1. Crush/grind
2. With ethanol / alcohol;
3. Then add water / then add to water;
4. Forms emulsion / goes white / cloudy;

Question 3

The structure of a phospholipid molecule is different from that of a triglyceride.
Describe how a phospholipid is different. (2m)

Answer 3

1. Phosphate / PO4;
   “It” refers to phospholipid.
2. Instead of one of the fatty acids / and two fatty acids;

Question 4

Use the diagram to explain what is meant by an unsaturated fatty acid. (2m)

Answer 4

1. Double bonds (present) / some / two carbons with only one
   hydrogen / (double bonds) between carbon atoms / not saturated
   with hydrogen;

2.In (fatty acid) C

Question 5

Describe how a triglyceride molecule is formed.

Answer 5

1. One glycerol and three fatty acids;
2. Condensation (reactions) and removal of three molecules of water;
3. Ester bond(s) (formed);

Question 6

Describe how an ester bond is formed in a phospholipid molecule. (2m)

Answer 6

1. Condensation (reaction)
   OR
   Loss of water;
2. Between of glycerol and fatty acid;