1.4.4 Blood cholesterol, HDLs and LDLs Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 1

The 20 questions

1. Which lipoprotein carries cholesterol from the liver to the body's tissues?

   • Fibrinogen
   • High-density lipoprotein (HDL)
   • Low-density lipoprotein (LDL)
   • Haemoglobin

2. Which lipoprotein is thought to remove cholesterol from the artery walls and return it to the liver?

   • High-density lipoprotein (HDL)
   • Low-density lipoprotein (LDL)
   • Prothrombin
   • Thromboplastin

3. Why are high LDL levels considered a risk factor for CVD?

   • LDL delivers cholesterol into artery walls, where it contributes to plaque formation
   • LDL removes cholesterol from the artery walls, which leaves the endothelium exposed
   • LDL raises blood pressure directly by increasing the viscosity of the blood
   • LDL is converted into fibrinogen, which blocks the arteries as a clot

4. Why are high HDL levels generally considered protective against CVD?

   • HDL increases the blood pressure, which pushes cholesterol out of the artery walls
   • HDL dissolves platelets, which prevents clots from forming on plaques
   • HDL delivers cholesterol into artery walls, which strengthens the arteries against plaque
   • HDL helps to remove excess cholesterol from tissues and transport it to the liver for disposal

5. A patient has a total cholesterol of 6.0 mmol/dm^3 and an HDL cholesterol of 1.2 mmol/dm^3. What is the ratio of total cholesterol to HDL cholesterol?

   • 5
   • 1.2
   • 0.2
   • 7.2

6. Which evidence most strongly supports a causal link between LDL cholesterol and CVD?

   • A single case study of a patient with high LDL who developed a heart attack
   • A cross-sectional survey showing that LDL and CVD are both common in older people
   • Observational data showing that people with high LDL tend to have more CVD than those with low LDL
   • Randomised trials showing that lowering LDL with drugs such as statins reduces CVD events

7. A statin trial reduces LDL cholesterol by 1 mmol/dm^3 and CVD events fall in the treated group. Which conclusion is best supported?

   • The reduction in LDL is linked to the fall in events, which supports a causal role for LDL
   • LDL has no effect on CVD, because statins also work through other mechanisms that cause the fall
   • The fall in events is entirely due to the placebo effect, which means LDL is irrelevant
   • The trial proves that LDL causes CVD in every person, regardless of other risk factors

8. Which of these is a common cause of high LDL cholesterol levels?

   • A diet high in unsaturated fat from vegetable oils
   • A diet high in saturated fat
   • Regular moderate exercise, which increases LDL clearance from the blood
   • A diet high in fibre from wholegrain cereals

9. Which statement about cholesterol in the body is correct?

   • Cholesterol is a carbohydrate that is stored in the liver as glycogen for quick energy release
   • Cholesterol is an enzyme that converts fibrinogen into fibrin during clotting
   • Cholesterol is a protein that forms the fibrin mesh of blood clots and stops bleeding
   • Cholesterol is needed to make cell membranes and steroid hormones, as well as being part of plasma lipoproteins

10. Why are lipoproteins needed to transport cholesterol in blood plasma?

    • Cholesterol must be converted into glycogen before it can be carried in the blood
    • Cholesterol is charged, so it must be carried by lipoproteins that neutralise its charge
    • Cholesterol is soluble in water, but it must be carried by lipoproteins to reach the liver
    • Cholesterol is insoluble in water, so it must be carried in lipoproteins that are soluble in plasma

11. Which measurement is most useful in judging the risk of CVD from blood cholesterol data?

    • Concentration of glucose in the blood after a meal, measured in mmol/dm^3
    • Number of red blood cells per mm^3 of whole blood
    • Concentration of thromboplastin in plasma after the onset of injury
    • Ratio of total cholesterol to HDL cholesterol, together with LDL level

12. A study reports that people with LDL above 4 mmol/dm^3 have a 3 times higher rate of CVD than those below 2 mmol/dm^3. Which is the most appropriate limitation to consider?

    • The study must have used too few people to measure LDL, which means the result is irrelevant
    • Other risk factors such as smoking and blood pressure may differ between the groups
    • LDL levels are always the same in all people, so any difference must be an error
    • The rate of CVD cannot be measured in humans, so the result must be invalid

13. Which of these is the best definition of an atherogenic lipoprotein?

    • A lipoprotein that protects against plaque formation by removing cholesterol from the blood
    • A lipoprotein that promotes deposition of cholesterol in artery walls, such as LDL
    • A fatty acid that is hydrolysed to form glycerol in adipose tissue
    • A protein that catalyses the breakdown of cholesterol in the liver

14. Why do doctors often measure total cholesterol and HDL cholesterol together?

    • The two values are always identical in every patient, so measuring both gives no extra information about risk
    • Total cholesterol is measured only in children, so HDL is needed in adult patients to check their risk level
    • The HDL to total cholesterol ratio gives information about cardiovascular risk beyond total cholesterol alone
    • HDL is a measure of blood glucose, so it must always be reported alongside total cholesterol in clinical tests

15. A patient with high LDL is prescribed a drug that reduces LDL by 40%. Which is the most accurate prediction for the drug's effect?

    • Reduced cholesterol delivery to artery walls, which may slow plaque growth and lower CVD risk
    • Increased HDL production, which causes the artery walls to thicken and block the lumen
    • Increased LDL production in the liver, which speeds up the clearance of plaque from the arteries
    • No change in plaque, because LDL does not affect the artery walls at all

16. Which of these is a dietary source of cholesterol?

    • Egg yolk, which is an animal product
    • Olive oil, which is a plant product rich in unsaturated fat
    • Fruit juice, which is rich in sugars such as fructose
    • Wholegrain bread, which is rich in fibre and starch

17. How do statins lower blood cholesterol?

    • They dissolve plaque in artery walls, so cholesterol is released into the lumen where the liver clears it
    • They inhibit an enzyme needed to make cholesterol in the liver, so the liver takes more LDL from the blood
    • They block the absorption of starch in the small intestine, which lowers cholesterol levels in the blood plasma
    • They increase the rate at which LDL is converted into HDL in the blood, which clears cholesterol from plasma

18. Which statement about the relationship between HDL and LDL is correct?

    • They are both carbohydrates that are stored in the liver as an energy source
    • They are the same molecule, which is only classified differently by density
    • They are both enzymes that catalyse the breakdown of cholesterol in the blood
    • They are both lipoproteins, but they have different roles in transporting cholesterol

19. A researcher finds that a group with high HDL has fewer heart attacks, and concludes HDL prevents heart attacks. Which is the most appropriate evaluation?

    • The result proves HDL prevents heart attacks in every person because the association is strong
    • The result is invalid, because HDL can have no effect on any aspect of heart health
    • The result shows an association, and a causal role for HDL would need controlled evidence
    • The result shows that heart attacks cause HDL to increase, which is the only possible explanation

20. What is the main role of the liver in cholesterol metabolism?

    • It breaks down all cholesterol into glucose, which is used in respiration by the body
    • It converts cholesterol into fibrinogen, which is needed for clot formation in the blood
    • It synthesises cholesterol and packages it into lipoproteins for transport in the blood
    • It stores cholesterol as glycogen, which is released during fasting to supply energy

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