paper 1: lipids

Question 1

what are the 2 groups of lipids called

Answer 1

1. triglycerides
2. phospholipids

Question 2

describe the role of each type of lipid

Answer 2

• triglycerides: energy storage, found in food
• phospholipids: important component of cell membranes

Question 3

describe the biochemical test for lipids

Answer 3

• crush sample
• add ethanol and shake
  -then add waterand shake
• white emulsion forms if lipid is present

Question 4

describe the structure of triglycerides and draw a diagram

Answer 4

Question 5

explain how triglycerides form

Answer 5

• one glycerol and 3 fatty acids join together by ester bonds that form in a condensation reaction and release 3 water molecules

Question 6

what is the general formula for a fatty acid

Answer 6

RCOOH

Question 7

draw a diagram of a saturated fatty acid

Answer 7

Question 8

draw a diagram of an unsaturated fatty acid

Answer 8

Question 9

explain the difference between saturated and unsaturated fatty acid

Answer 9

saturated fatty acids do not contain double bonds between carbon atoms in the hydrocarbon chain whereas unsaturated fatty acids contain double bonds between carbon atoms in the hydrocarbon chains

Question 10

describe the structure of phospholipids

Answer 10

phospholipid contains one glycerol, 2 fatty acids and one phosphate group

Question 11

describe and explain how phospholipids arrange themselves in cell membranes

Answer 11

the hydrophobic fatty acid tails are arranged in the middle away from the water and the hydrophilic heads are arranged on the outside in contact with water

Question 12

compare and contrast the structure of triglycerides and phospholipids

Answer 12

• triglycerides have long hydrocarbon fatty acid chains
• phospholipids have hydrophilic phosphate heads
  + they both have hydrophobic fatty acid tails

Question 13

compare and contrast the properties of triglycerides and phospholipids

Answer 13

• triglycerides contains lots of stored chemical energy
• triglycerides are insoluble in water whereas phospholipids will form a phospholipid bilayer with hydrophobic fatty acid tails pointing in away from the water and hydrophilic phosphate heads pointing out towards the water

Question 14

define hydrophobic

Answer 14

repels water

Question 15

define hydrophilic

Answer 15

attracts water

Question 16

describe how triglycerides behave in water

Answer 16

• clump together with fatty acid tails facing inwards
• form insoluble droplets