2.47 Diseases associated with Smoking: A* understanding for iGCSE Biology

The health risks of smoking cigarettes and other tobacco products are well understood.  But in iGCSE exams, it can sometimes be difficult to work out exactly how much detail the examiner wants, especially on an open-ended question.  This blog post is an attempt to demonstrate some of the key areas of understanding that you should be aiming to show in your answers.

cigarette

Cigarettes contain a wide variety of toxic chemicals: you should focus your understanding on three examples.

Nicotine is the stimulant drug found in cigarette smoke and also the reason smokers can easily become dependent on smoking.  Nicotine is rapidly absorbed into the blood in the lungs and it causes an increase in heart rate, an increase in blood pressure and the release of the hormone adrenaline (which has similar effects).

Carbon Monoxide is a poisonous gas that is produced whenever there is incomplete combustion of biological material.  Carbon monoxide binds to haemoglobin in the red blood cells in place of oxygen and so the smoker will be transporting less oxygen in her blood, and this leads to a whole load of implications for health.

Tar is the name given to a large number of different chemicals found in cigarette smoke.  Tar forms droplets in the smoke which can condense in the airways and alveoli.  Many of the chemicals in Tar are carcinogens – that means they promote the formation of cancer.  Tar also damages the cilia in the trachea and bronchi and makes the thin walls of the alveoli lose their elasticity and so damage more easily.

Diseases of the Lungs associated with Smoking

Risks_form_smoking-smoking_can_damage_every_part_of_the_body

1) Emphysema

Emphysema is a disease in which the thin walls of the alveoli break down.  Tar droplets condense onto the alveolar wall, making them rigid and inflexible.  Smokers are coughing a great deal to remove the mucus from their lungs and this coughing can cause the sticky, rigid tar coated alveolar wall to degenerate.

Emphysema_Diagram RsVntl67

A patient with emphysema will have a greatly reduced surface area for gas exchange due to all the collapsed alveoli.  So the diffusion of oxygen into the blood would be reduced causing breathlessness and impacting health.

2) Chronic Bronchitis

The bronchi can become inflamed and narrowed due to the overproduction of mucus and the fact that the muco-ciliary escalator does not function to waft mucus up the bronchi.  A narrowed bronchus makes breathing harder and compounds the problems of emphysema described above.  It also promotes coughing which damages the alveoli still further.

chronic-bronchitis

3) Lung cancer

Carcinogens in cigarette smoke can make it much more likely that cells in the lungs and airways develop mutations that lead to cancer.  Cancer is a disease in which cells start to divide out of control to form a tumour and then cells in the tumour break off and travel round the bloodstream to form secondary tumours elsewhere in the body.  Lung cancers can be hard to treat and are a common cause of early death in cigarette smokers.

Lung_Cancer

Diseases of the Cardiovascular System associated with Smoking

It is not just the lungs that are affected in patients who smoke.  Cigarette smoking is a significant risk factor in the commonest cause of death in the UK: coronary heart disease (CHD)

CHD is a disease in which the arteries that supply the cardiac muscle in the heart (the coronary arteries) get narrowed due to the build up of fatty plaque in their walls.  This is a condition called atherosclerosis.  A narrowed coronary artery means that an area of cardiac muscle is starved of oxygen and so can die.  This may interfere with the electrical coordination of the heart beat causing a cardiac arrest or heart attack.

images_235 Heart-&-narrowed-artery

Patients who smoke have a higher blood pressure than normal due to the stimulant effects of nicotine.  A high blood pressure makes the early damage to the arterial lining more likely as well as making the blood more likely to clot.   Blood clots form in the final stages of the disease around the plaque and can complete block the blood vessel.  CHD is a major cause of death across the world and it is well known that stopping smoking can do a great deal to lower a patient’s risk of this potentially deadly disease.

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22 comments

  1. Ben Askey-Wood

    I don’t really have any biological questions yet, as you seem to have explained them quite well, but where did nicotine come from, or did it come from something like a tobacco plant

    • Paul Gillam

      Nicotine is a chemical made by the tobacco plant and stored in its leaves to prevent herbivores from eating them. It is extremely toxic to insects that might want to eat tobacco leaves.

    • Paul Gillam

      This is too complicated a question for a short response. Marijuana contains a psychoactive chemical called THC that affects nerve cells. There is good evidence for Marijuana smokers having a greatly increased risk of schizonphrenia and other psychiatric conditions. Marijuana is usually mixed with tobacco and so smokers are also at risk of all the cancers and heart disease associated with tobacco.

    • Paul Gillam

      I’m sure that’s right. The interesting issue is why people continue to smoke when they understand how it harms them. Nicotine is an addictive drug but that alone does not explain people’s dependence on smoking.

  2. Garfield Weston

    Other than binding onto the red blood cells and reducing the amount of oxygen that can flow into the body, is carbon monoxide dangerous and why does it not form instead of carbon dioxide? Is it less stable?

  3. Nico Lurz

    Sir couldn’t you stop CHD by taking arteries from dead “healthy” bodies and then replace the blocked up ones from which you get from smocking to solve the problem of so many people dying?

    • Paul Gillam

      The problem with your solution is two-fold. Firstly we have a shortage of donors for organ transplantation. Secondly the recipient’s immune system would mount an immune response and the transplanted artery would be rejected. So in practice, either a section of vein from the same patient is strengthened and use (no rejection) or an artificial tube is made using a synthetic polymer. Good question though…..

  4. Lucas Ipkendanz

    Do different cigarette companies put more carcinogens in their products, if so cigarette will affect your body the most?

    • Paul Gillam

      The biological effects are similar. Cigar smokers tend not to inhale the smoke into their lungs, so the get cancers of the mouth and tongue and are not at so much risk of emphysema or bronchitis.

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