Lipids

Question 1

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.

the risk is going down as you eat more omega 3

Do the data show that eating omega-3 fatty acids prevents coronary heart disease? Explain your answer.

Answer 1

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 2

Use the information in the figure to explain two ways in which fatty acids are important in the formation of new cells

INFO used to make plasma membranes
fatty acids respired for energy
Used to make other fatty acids

Answer 2

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

2 max

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

Question 3

Cholesterol increases the stability of plasma membranes. Cholesterol does this by making membranes less flexible.

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

Answer 3

Red blood cells free in blood / not supported by other cells so cholesterol helps to maintain shape;

Question 4

The scientists expressed their results as Percentage of lipid in plasma membrane by mass. Explain how they would find these values

Answer 4

Divide mass of each lipid by total mass of all lipids (in that type of cell);

2. Multiply answer by 100.