3. lipids

Question 1

(3)

Answer 1

1. Fewer children / less likely that children with asthma eat fish;
2. Fewer children / less likely that children with asthma eat oily fish;
3. Little / only 2% / no difference in (children with or without asthma who
   eat) non-oily fish.

Question 2

(4)

Answer 2

Fatty acids used to make phospholipids;
Phospholipids in membranes;
More phospholipids more membranes made;

Fatty acids respired to release energy;
More triglycerides more energy released;
Energy used for cell production / production of named cell component;

Question 3

Hydrogen bonds are important in cellulose molecules. Explain why. (2)

Answer 3

1. Holds chains / cellulose molecules together / forms cross links
   between chains / cellulose molecules / forms microfibrils, providing
   strength / rigidity (to cellulose / cell wall);
2. Hydrogen bonds strong in large numbers;x

Question 4

A starch molecule has a spiral shape. Explain why this shape is important to
its function in cells.

Answer 4

Compact / occupies small space / tightly packed;

Question 5

Omega-3 fatty acids are unsaturated. What is an unsaturated fatty acid?

Answer 5

Double bond(s);

(Bonds) between carbon;

Question 6

Scientists investigated the relationship between the amount of omega-3 fatty acids eaten per day and the risk of coronary heart disease. The graph shows their results.(3)

Answer 6

Graph shows negative correlation / description given;
Correlation does not mean causation / prevention / shows lower risk not
prevention;
May be due to another factor / example given;

Question 7

Olestra is an artificial lipid. It is made by attaching fatty acids, by condensation, to a
sucrose molecule. The diagram shows the structure of olestra. The letter R shows
where a fatty acid molecule has attached.
(i) Name bond X.
(ii) A triglyceride does not contain sucrose or bond X. Give one other way in
which the structure of a triglyceride is different to olestra.
(iii) Starting with separate molecules of glucose, fructose and fatty acids, how
many molecules of water would be produced when one molecule of olestra is
formed?

Answer 7

(i) Glycosidic;
(ii) Contains glycerol / three fatty acids / forms three ester bonds;
(iii) 9;

Question 8

Answer 8

(i) 4 / four;

Question 9

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

Answer 9

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

Question 10

explain what is meant by an unsaturated fatty acid. (2)

Answer 10

1. Double bonds (present) / some / two carbons with only one
   hydrogen / (double bonds) between carbon atoms / not saturated
   with hydrogen;
   Answer refers to unsaturated unless otherwise clearly
   indicated.
   May be shown in appropriate diagram.
2. In (fatty acid)

Question 11

(2)

Answer 11

Two suitable suggestions;

E.g.
1. (Are mammals so) likely to have same physiology / reactions as humans;
2. Small enough to keep in laboratory / produce enough milk to extract;
3. (Can use a) large number.

Question 12

Before starting their experiments, the scientists confirmed that, like human breast
milk, cat’s milk also contained bile-activated lipase.
To do this, they added bile to cat’s milk and monitored the pH of the mixture.
Explain why monitoring the pH of the mixture could show whether the cat’s milk
contained lipase. (2)

Answer 12

1. Hydrolysis of lipids produces fatty acids;
2. Which lower pH of mixture.

Question 13

(3)

Answer 13

1. (Bile-activated lipase / it) increases growth rate (of kittens);
2. Results for formula with lipase not (significantly) different from breast
   milk / are (significantly) different from formula milk alone;
3. Showing addition of (bile-activated) lipase is the likely cause (of
   increased growth);
4. Lipase increases rate of digestion of lipids / absorption of fatty acids.

Question 14

Answer 14

1. Unsaturated (fatty acid/hydrocarbon);
2. Double bond (between carbons);

Question 15

Describe how a triglyceride molecule is formed. (3)

Answer 15

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

Question 16

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

Answer 16

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