AQA GCSE Biology (8461) — Biological Organisation
Think about a blocked pipe under your kitchen sink — water cannot get through, and eventually, the entire system backs up. Coronary Heart Disease (CHD) works in a similar way and is a non-communicable condition affecting the heart. It is caused by the buildup of layers of fatty material inside the walls of the coronary arteries.
These arteries are crucial because they branch off the aorta to supply the heart muscle with oxygenated blood. When fatty deposits build up, the lumen (the central space) of the artery becomes narrower.
This narrowing severely restricts blood flow, meaning less oxygen and glucose reach the heart muscle cells. Without these essential molecules, the cells cannot perform aerobic respiration to release the energy needed for muscle contraction.
A partial blockage can cause angina (chest pain) due to cells switching to anaerobic respiration, which releases less energy and produces lactic acid. A complete blockage results in a heart attack, where heart muscle cells die from a complete lack of energy.
How do you keep a collapsing tunnel open? You put up strong scaffolding to hold the walls apart. A stent is a metal mesh tube inserted into narrowed coronary arteries to mechanically hold the lumen open. It provides an immediate physical solution to severe blockages.
During the procedure, a tiny balloon is placed inside the stent and inflated to expand the mesh, pushing the fatty deposits against the artery wall. The balloon is then removed, leaving the stent in place permanently. By widening the lumen, stents restore healthy blood flow to the heart muscle, ensuring a constant supply of oxygen and glucose.
While stents are highly effective and have a quick recovery time, they carry surgical risks. A specific danger is thrombosis, which is the formation of a blood clot near the stent.
Many older adults take a small tablet every single morning just to keep their blood chemistry perfectly balanced. are medicinal drugs prescribed as a (preventative) treatment to lower blood levels. Cholesterol is an essential lipid, but too much "bad" cholesterol (LDL) leads to dangerous fatty deposits.
Statins work by blocking a specific enzyme in the liver that is responsible for producing cholesterol. By lowering LDL levels in the blood, statins successfully slow down the rate at which fatty material builds up in the arteries. They can also increase the levels of HDL, which is the "good" cholesterol that helps remove existing fatty deposits.
Doctors must carefully weigh the immediate physical benefits of surgery against the long-term commitment of daily medication when treating a patient. In exams, you may be asked to compare these two distinct treatment pathways.
| Feature | Stents (Mechanical Treatment) | Statins (Medicinal Treatment) |
|---|---|---|
| Mechanism | Widens the lumen to mechanically restore blood flow. | Lowers blood cholesterol to slow the buildup of fatty material. |
| Advantages | Immediate physical fix; long-lasting; relatively quick recovery from surgery. | Non-invasive (no surgical risks); increases good cholesterol (HDL); inexpensive compared to surgery. |
| Disadvantages | Risk of thrombosis (blood clots); surgical risks such as infection. | Must be taken daily long-term; possible side effects (muscle pain, liver damage); takes time for cholesterol levels to drop. |
Students often say that CHD reduces blood flow "to the heart" — you must specify that it reduces blood flow to the heart muscle cells, not the chambers of the heart.
Never write that energy is "produced" or "made" during respiration; always state that energy is released.
In 6-mark pathology questions, examiners expect a step-by-step causal chain: state the buildup of fatty material, the narrowing of the lumen, the reduced blood flow, and the resulting lack of both oxygen AND glucose.
Always use the exact phrase "fatty material" or "fatty deposits" rather than just saying "fat" when describing blockages in the arteries.
Coronary Heart Disease (CHD)
A condition where coronary arteries are narrowed by the buildup of fatty material, reducing blood flow and oxygen supply to the heart muscle.
Non-communicable
A disease that cannot be spread from person to person.
Fatty material
Deposits (also called plaques or atheroma) that build up inside the walls of arteries, causing them to narrow.
Coronary arteries
The blood vessels that branch off the aorta to supply the heart muscle with oxygenated blood.
Heart muscle
The tissue (myocardium) that requires a continuous supply of oxygen and glucose to release energy for contraction.
Lumen
The central channel or inside space of a tubular structure, such as an artery, through which blood flows.
Aerobic respiration
The chemical process in cells that uses oxygen to break down glucose and release energy.
Stent
A mechanical device (metal mesh tube) used to widen the lumen of a narrowed coronary artery.
Thrombosis
The formation of a blood clot within a blood vessel, a specific risk associated with stent placement.
Statins
Medicinal drugs used to lower blood cholesterol levels to slow the rate of fatty material buildup.
Prophylactic
A preventative treatment or medication used to stop a disease from occurring.
Cholesterol
An essential lipid found in the blood; however, excess LDL cholesterol causes fatty deposits in the arteries.
Put your knowledge into practice — try past paper questions for Biology
Coronary Heart Disease (CHD)
A condition where coronary arteries are narrowed by the buildup of fatty material, reducing blood flow and oxygen supply to the heart muscle.
Non-communicable
A disease that cannot be spread from person to person.
Fatty material
Deposits (also called plaques or atheroma) that build up inside the walls of arteries, causing them to narrow.
Coronary arteries
The blood vessels that branch off the aorta to supply the heart muscle with oxygenated blood.
Heart muscle
The tissue (myocardium) that requires a continuous supply of oxygen and glucose to release energy for contraction.
Lumen
The central channel or inside space of a tubular structure, such as an artery, through which blood flows.
Aerobic respiration
The chemical process in cells that uses oxygen to break down glucose and release energy.
Stent
A mechanical device (metal mesh tube) used to widen the lumen of a narrowed coronary artery.
Thrombosis
The formation of a blood clot within a blood vessel, a specific risk associated with stent placement.
Statins
Medicinal drugs used to lower blood cholesterol levels to slow the rate of fatty material buildup.
Prophylactic
A preventative treatment or medication used to stop a disease from occurring.
Cholesterol
An essential lipid found in the blood; however, excess LDL cholesterol causes fatty deposits in the arteries.
