·
When it comes to AS/A-level Biology, do you remember how smoking causes lung cancer?
Nicotine
Nicotine in cigarettes affects the lungs by:
- Causing the bronchioles in the lungs to constrict – this reduces the air flow in and out of the lungs.
- Paralysing cilia which are meant to remove the dirt and bacteria from the trachea.
- Raising blood pressure and heart rate – this increases the risk of CHD.
Carbon Monoxide
- Carbon Monoxide poisons the red blood cells by attaching to the haemoglobin which means that oxygen will not be able to be carried by the haemoglobin – oxygen won’t be delivered to cells and muscle tissue around the body.
- This can cause a reduction in the ability to do hard exercise, breathlessness and an increase in the risk of heart disease and the heart’s muscle tissue need the oxygen to pump the blood and stay alive.
Tars
- Tars can stick to cells in the lungs and release carcinogenic free radicals into the cells which increases the risk of cancer, especially in the lungs.
- Free radicals are unstable, chemically incomplete substances that ‘steal’ electrons from other molecules.
- Highly reactive chemicals which can damage other chemicals such as enzymes, reducing their efficiency.
- Tars can also damage DNA – this may lead to cancers.
- Medical scientists believe that free radicals contribute to at least 50 other major diseases including atherosclerosis, heart disease and lung disease.
- Anti-oxidants in our diet (especially Vitamins A, C and E) get rid of free radicals which enables us to cope with small amounts.
- In the UK, it is estimated that the need for Vitamin C of smokers could be twice as much as non-smokers.
- Tars can irritate and damage the lung tissue both mechanically and chemically – this can lead to emphysema and bronchitis.
Emphysema and Bronchitis
- Emphysema is caused by a breakdown of the thin walls of the alveoli, decreasing the total surface area for gas exchange.
- Symptoms including chronic breathlessness, coughing, wheezing and a reduction in the tolerance for exercise.
- Bronchitis is an inflammation in the linings of the airways to the lungs.
- Acute bronchitis lasts usually only a few days and is more commonly associated with colds.
- Chronic bronchitis is much more serious and is responsible for about 30,000 deaths each year in Britain.
- Coughing associated with bronchitis usually contributes to the development of emphysema.

Pulmonary Fibrosis
- It refers to the permanent scarring of lung tissue.
- It can be caused by many conditions including Infections, environmental agents and exposure to ionizing radiation (such as radiation therapy to treat tumours of the chest).
- Sometimes it develops as an autoimmune response to inhaling dusts contaminated with bacterial, fungal or animal products.
- In some people, it develops without any identifiable cause.
- It results in a shortness of breath, coughing and reduced exercise tolerance.
- Lung function tests give distinctly abnormal results which worsen over time.

That's the end of the topic!

Drafted by Bonnie (Biology)