A group of adults took part in a health study. Those who reported eating a diet high in saturated fat had higher levels of low-density lipoprotein (LDL) cholesterol in their blood. Explain how a high level of LDL cholesterol in the blood increases the risk of a heart attack.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A group of adults took part in a health study. Those who reported eating a diet high in saturated fat had higher levels of low-density lipoprotein (LDL) cholesterol in their blood.
Model answer (5 marks)
LDL cholesterol particles deposit in the intima of coronary arteries, forming atheromatous plaques.
These plaques narrow the arterial lumen, reducing blood flow to the myocardium.
The plaque surface can be disrupted, providing a site for platelet adhesion and thrombus formation.
A thrombus can occlude the coronary artery completely.
When the artery is blocked, heart muscle cells are deprived of oxygen and glucose, they cannot perform aerobic respiration, leading to cell death – a heart attack.
These plaques narrow the arterial lumen, reducing blood flow to the myocardium.
The plaque surface can be disrupted, providing a site for platelet adhesion and thrombus formation.
A thrombus can occlude the coronary artery completely.
When the artery is blocked, heart muscle cells are deprived of oxygen and glucose, they cannot perform aerobic respiration, leading to cell death – a heart attack.
Examiner tips
- Use the exact terms ‘LDL’, ‘plaque’, ‘thrombus’, ‘occlusion’, ‘myocardium’
- Show the causal chain from LDL to plaque to clot to cell death
- Keep each point brief but complete
- Use correct UK spelling
Common mistakes
- Confusing HDL with LDL
- Failing to mention the plaque narrowing the lumen
- Not linking the clot to complete blockage
Mark scheme (5 marks)
- LDL cholesterol deposits build up inside the walls of coronary arteries (forming plaques / atheroma)
- This narrows the lumen of the coronary arteries (reducing blood flow to the heart muscle)
- A blood clot (thrombus) can form at the site of a plaque
- The clot can completely block the coronary artery
- Heart muscle cells are deprived of oxygen / glucose and so cannot respire, causing them to die — resulting in a heart attack
Key terms in this question
LDL cholesterol · heart attack
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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