3.1.3 - LIPIDS

Question 1

the general structure of a fatty acid is RCOOH. name the group represented by COOH (1)

Answer 1

carboxyl group

Question 2

describe how you would test for the presence of a lipid in a liquid sample of food (2)

Answer 2

1. add ethanol/alcohol then add water and shake/mix
2. white/milky emulsion

Question 3

describe how a triglyceride molecule is formed (3)

Answer 3

1. one glycerol and three fatty acids
2. condensation reactions and removal of three molecules of water
3. ester bonds formed

Question 4

describe how an ester bond is formed in a phospholipid molecule (2)

Answer 4

1. condensation reaction
2. between glycerol and fatty acid

Question 5

describe how you would test a piece of food for the presence of lipid (2)

Answer 5

1. dissolve the sample in alcohol, then add water
2. white/milky emulsion

Question 6

name the type of bond between a glycerol and fatty acid (1)

Answer 6

ester bond

Question 7

a triglyceride is formed by condensation. from how many molecules is this triglyceride formed from? (1)

Answer 7

4

Question 8

the structure of a phospholipid molecule is different from that of a triglyceride. describe how a phospholipid is different. (2)

Answer 8

1. addition of a phosphate group
2. instead of one of the fatty acids

Question 9

omega-3 fatty acids are unsaturated. what is an unsaturated fatty acid? (2)

Answer 9

when double bonds are present between carbon atoms