Lipids

Question 1

Describe how a triglyceride molecule is formed (3)

Answer 1

-condensation reaction AND removal of three water molecules
-one glycerol and three fatty acids
-forms ester bond

Question 2

How is an ester bond in a phospholipid molecule? (2)

Answer 2

-condensation reaction
-glycerol and fatty acid

Question 3

Suggest one advantage of the different percentage of cholesterol in red blood cells compared with the cells lining the ileum (2)

Answer 3

-rbc free/not supported by other cells
-cholesterol helps maintain its shape

Question 4

E.coli has no cholesterol yet it can maintain its shape. Why? (2)

Answer 4

-cells can’t change shape
-has cell wall

Question 5

Suggest two reasons of using cats to see benefits of breast milk (2)

Answer 5

-can use large numbers
-same reaction as humans

Question 6

Cat milk contains bile-activated lipase like breast milk. They added bile to it. Why is monitoring the pH of the mixture able to show whether cat milk has lipase? (2)

Answer 6

-lipase hydrolysed lipids to fatty acid tails
-lowers pH

Question 7

How is the structure of a triglyceride different of a phospholipid? (2)

Answer 7

-phosphate in phospholipid
-2 fatty acids in phospholipid but 3 in triglyceride

Question 8

What is an unsaturated fatty acid? (2)

Answer 8

-double bond
-between carbon atoms

Question 9

Why does a stained cell surface membrane show up as two dark lines? (3)

Answer 9

Membrane is phospholipid bilayer stain
-binds to phospholipid
-on inside and outside of membrane