Edexcel GCSE Biology (1BI0) — Health, Disease and Medicines
The liver is the body's primary filtration system, but processing certain chemicals actually produces toxins that destroy it. Drinks contain ethanol, a specific type of alcohol that acts as a toxin. When ethanol is absorbed into the blood and transported to the liver, specialized liver cells called hepatocytes break it down.
This breakdown process produces highly toxic products (such as acetaldehyde). Over time, repeated exposure to these toxins damages and kills hepatocytes. The earliest stage of alcohol-induced damage is fatty liver disease, where fat accumulates in the liver cells and prevents them from functioning normally. If a person stops drinking alcohol, this early stage is often reversible.
Long-term, heavy drinking leads to cirrhosis. This is a chronic non-communicable disease where the repeated death of liver cells causes healthy tissue to be permanently replaced by non-functional scar tissue (fibrosis).
Understanding liver failure explains why severe alcohol abuse affects almost every other organ in the body. Because scar tissue cannot perform the normal metabolic functions of healthy liver cells, cirrhosis is generally irreversible and leads to severe, widespread complications.
Alcohol is also a known carcinogen, meaning it drastically increases the risk of developing liver cancer.
Why does inhaling smoke into the lungs cause diseases of the heart and blood vessels? Tobacco smoke contains chemicals that enter the bloodstream and directly damage the cardiovascular system, primarily carbon monoxide and nicotine.
Carbon monoxide binds permanently to haemoglobin in red blood cells, forming a stable complex called carboxyhaemoglobin. Because haemoglobin has an affinity for carbon monoxide that is 200–250 times higher than for oxygen, the blood's overall oxygen-carrying capacity is severely reduced. To compensate for the lack of circulating oxygen, the heart must pump much faster, which increases heart rate and places immense strain on the cardiovascular system.
Nicotine acts as a stimulant that triggers the release of adrenaline. This causes vasoconstriction, which is the narrowing of the blood vessels, further raising blood pressure. Nicotine also makes blood platelets sticky, significantly increasing the risk of thrombosis (blood clots).
Think of a clean pipe gradually becoming clogged with thick grease until water can barely trickle through. Atherosclerosis is the process where arteries harden and narrow due to the buildup of fatty plaques.
High blood pressure and toxic chemicals in tobacco smoke damage the endothelium (the inner lining of the artery). This damage triggers the accumulation of fatty deposits called atheroma (or plaques), which are composed of cholesterol and lipids.
As these plaques build up, the lumen (the central space inside the vessel) gradually narrows. The artery walls lose their elasticity and harden, which creates a vicious cycle by further increasing blood pressure.
A person carrying heavy shopping feels a sudden, crushing chest pain. This occurs when atherosclerosis affects the coronary arteries, restricting blood flow and oxygen to the heart muscle. A partial blockage causes angina (severe chest pain).
If sticky platelets form a clot that completely blocks the narrowed coronary artery, the heart muscle is entirely deprived of oxygen. The cells cannot respire aerobically, so they switch to anaerobic respiration, producing lactic acid. Eventually, the muscle cells die. This is called a heart attack (myocardial infarction). Similarly, if a blood clot or ruptured plaque blocks an artery supplying the brain, it deprives brain tissue of oxygen, causing a stroke.
Medical professionals use numerical scales to compare the danger of different lifestyle choices. A non-drinker has a baseline relative risk of for developing cirrhosis. A person consuming units of alcohol per week on an empty stomach has a relative risk of . Consuming the same amount of alcohol alongside meals reduces this elevated relative risk by . Calculate the new relative risk for a person drinking units with meals.
Step 1: Identify the initial high risk.
Step 2: Calculate the reduction amount.
Step 3: Subtract the reduction from the initial risk to find the final answer.
Students often confuse the effects of tar with carbon monoxide and nicotine. Remember that tar causes lung issues (like bronchitis), whereas carbon monoxide and nicotine specifically affect the cardiovascular system.
When answering questions about the effects of alcohol on the liver, always use the specific phrase 'scar tissue' or 'scarring' rather than vaguely stating the liver is 'damaged'.
In 6-mark questions explaining how smoking causes a heart attack, examiners look for a step-by-step causal chain: endothelium damage → atheroma buildup → lumen narrowing → restricted oxygen to the heart muscle → anaerobic respiration.
Remember to state that carbon monoxide binds permanently (or irreversibly) to haemoglobin; this specific keyword is often required to secure a mark on the Edexcel mark scheme.
Ethanol
The specific type of alcohol found in alcoholic drinks that acts as a toxin to liver cells.
Hepatocytes
Specialized liver cells responsible for breaking down toxins, including ethanol.
Fatty liver disease
The earliest, often reversible, stage of alcohol-induced liver damage where fat accumulates in liver cells.
Cirrhosis
A chronic disease where healthy liver tissue is permanently replaced by non-functional scar tissue.
Non-communicable disease
A disease that is not caused by a pathogen and cannot be passed from person to person.
Scar tissue
Non-functional fibrotic tissue that replaces healthy cells after repeated damage, such as in cirrhosis.
Jaundice
A yellowing of the skin and eyes caused by a buildup of bilirubin when the liver fails to process it.
Deamination
The process in the liver where excess amino acids are broken down, producing ammonia as a byproduct.
Carcinogen
A substance or chemical that significantly increases the risk of developing cancer.
Carbon monoxide
A toxic gas found in tobacco smoke that binds permanently to haemoglobin, reducing oxygen transport.
Nicotine
An addictive stimulant found in tobacco smoke that increases heart rate and causes vasoconstriction.
Haemoglobin
The red pigment in red blood cells that normally binds reversibly with oxygen to transport it around the body.
Carboxyhaemoglobin
A stable, permanent complex formed when carbon monoxide binds to haemoglobin.
Vasoconstriction
The narrowing of the blood vessel lumen due to the contraction of the muscular walls.
Thrombosis
The formation of a blood clot inside a blood vessel, which can block blood flow.
Atherosclerosis
The hardening and narrowing of arteries due to the buildup of fatty plaques (atheroma).
Endothelium
The delicate inner lining or cell layer of an artery.
Atheroma
Fatty deposits composed of cholesterol and lipids that build up in the artery walls.
Lumen
The central channel or empty space inside a blood vessel through which blood flows.
Put your knowledge into practice — try past paper questions for Biology
Ethanol
The specific type of alcohol found in alcoholic drinks that acts as a toxin to liver cells.
Hepatocytes
Specialized liver cells responsible for breaking down toxins, including ethanol.
Fatty liver disease
The earliest, often reversible, stage of alcohol-induced liver damage where fat accumulates in liver cells.
Cirrhosis
A chronic disease where healthy liver tissue is permanently replaced by non-functional scar tissue.
Non-communicable disease
A disease that is not caused by a pathogen and cannot be passed from person to person.
Scar tissue
Non-functional fibrotic tissue that replaces healthy cells after repeated damage, such as in cirrhosis.
Jaundice
A yellowing of the skin and eyes caused by a buildup of bilirubin when the liver fails to process it.
Deamination
The process in the liver where excess amino acids are broken down, producing ammonia as a byproduct.
Carcinogen
A substance or chemical that significantly increases the risk of developing cancer.
Carbon monoxide
A toxic gas found in tobacco smoke that binds permanently to haemoglobin, reducing oxygen transport.
Nicotine
An addictive stimulant found in tobacco smoke that increases heart rate and causes vasoconstriction.
Haemoglobin
The red pigment in red blood cells that normally binds reversibly with oxygen to transport it around the body.
Carboxyhaemoglobin
A stable, permanent complex formed when carbon monoxide binds to haemoglobin.
Vasoconstriction
The narrowing of the blood vessel lumen due to the contraction of the muscular walls.
Thrombosis
The formation of a blood clot inside a blood vessel, which can block blood flow.
Atherosclerosis
The hardening and narrowing of arteries due to the buildup of fatty plaques (atheroma).
Endothelium
The delicate inner lining or cell layer of an artery.
Atheroma
Fatty deposits composed of cholesterol and lipids that build up in the artery walls.
Lumen
The central channel or empty space inside a blood vessel through which blood flows.
