Cancer

1. 1 State [1 mark]

   State what is meant by cancer.

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   Model answer

   A disease caused by changes in cells which lead to uncontrolled cell division.

   Mark scheme

   • Uncontrolled cell division — 1 mark
2. 2 State [2 marks]

   State two risk factors for cancer.

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   Model answer

   Any two from: smoking, ultraviolet radiation, ionising radiation, some viruses such as HPV, inherited genes, obesity, alcohol, age.

   Mark scheme

   • First — 1 mark
   • Second — 1 mark
3. 3 Describe [3 marks]

   Describe the differences between a benign tumour and a malignant tumour.

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   Model answer

   A benign tumour grows in one place, and does not invade the neighbouring tissues, but a malignant tumour invades neighbouring tissues. Cells of a malignant tumour can spread in the blood to other parts of the body and form secondary tumours.

   Mark scheme

   • Benign stays in one place — 1 mark
   • Malignant invades neighbouring tissue — 1 mark
   • Malignant cells spread, forming secondary tumours — 1 mark
4. 4 Explain [3 marks]

   Explain why smoking increases the risk of lung cancer.

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   Model answer

   Tobacco smoke contains carcinogens, which can cause mutations in the DNA of lung cells. A mutation in a gene that controls cell division can cause a cell to divide in an uncontrolled way, which forms a tumour.

   Mark scheme

   • Smoke contains carcinogens — 1 mark
   • Cause mutations in DNA — 1 mark
   • Uncontrolled cell division forms a tumour — 1 mark
5. 5 Calculate [3 marks]

   A cancer cell divides once every 2 days. Assuming that no cells die, calculate how many cells there will be after 20 days, starting with one cell.

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   Model answer

   20 days at one division per 2 days gives 10 divisions. 2 to the power 10 is 1024 cells.

   Mark scheme

   • 10 divisions — 1 mark
   • 2 to the power 10 — 1 mark
   • 1024 cells — 1 mark
6. 6 Evaluate [6 marks]

   Evaluate the use of surgery, radiotherapy and chemotherapy in the treatment of cancer.

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   Model answer

   Surgery can remove a whole tumour, and is effective if the cancer has not spread, but it is not possible if the tumour is in a place that cannot be reached, or if it has already spread, and it carries the risks of any operation. Radiotherapy can be aimed at a particular tumour, and can kill cells that cannot be removed, but it also damages healthy tissue around it. Chemotherapy travels in the blood and can reach cancer cells all over the body, including those that have spread, but it also kills healthy cells that divide quickly, so it has side effects such as hair loss and sickness. The treatment chosen depends on the type of the cancer and on how far it has spread, and a combination is often used to give the best chance.

   Mark scheme

   • Surgery removes the tumour — 1 mark
   • Limits of surgery — 1 mark
   • Radiotherapy targets the tumour — 1 mark
   • Radiotherapy damages healthy tissue — 1 mark
   • Chemotherapy reaches the whole body but has side effects — 1 mark
   • Treatment depends on the cancer, and may be combined — 1 mark

Quick check

1. 1

   What is a tumour?

   1. AA virus
   2. BA mass of abnormal cells
   3. CA type of white blood cell
   4. DA cancer drug
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   B: A mass of abnormal cells

   A tumour is a lump of abnormal cells that divide in an uncontrolled way.

2. 2

   Which statement describes a malignant tumour?

   1. AIt never spreads
   2. BIt stays inside a membrane
   3. CIt invades other tissues and spreads
   4. DIt is not cancer
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   C: It invades other tissues and spreads

   Malignant tumours invade other tissues and spread.

3. 3

   What causes cells to become cancerous?

   1. AMutations in genes that control cell division
   2. BA lack of vitamins
   3. CToo much sleep
   4. DA virus in every case
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   A: Mutations in genes that control cell division

   Mutations in the genes that control cell division.

4. 4

   Which causes skin cancer?

   1. AEating fat
   2. BDrinking water
   3. CHeavy exercise
   4. DUltraviolet radiation
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   D: Ultraviolet radiation

   Ultraviolet radiation damages the DNA of skin cells.

5. 5

   What is a secondary tumour?

   1. AThe first tumour
   2. BA tumour formed by spread from another place
   3. CA benign tumour
   4. DA tumour in a child
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   B: A tumour formed by spread from another place

   A tumour that forms where cancer cells have spread to.

6. 6

   Why does chemotherapy cause hair loss?

   1. AIt makes hair dry
   2. BIt is a hair dye
   3. CIt harms healthy cells that divide quickly
   4. DIt affects the brain
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   C: It harms healthy cells that divide quickly

   It kills healthy cells that divide quickly, such as hair root cells.

7. 7

   Which is a way of reducing the risk of cancer?

   1. ANot smoking
   2. BEating more sugar
   3. CSunbathing
   4. DDrinking more alcohol
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   A: Not smoking

   Not smoking reduces the exposure to carcinogens.

8. 8

   A cancer cell divides once a day. How many cells after 5 days?

   1. A5
   2. B10
   3. C25
   4. D32
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   D: 32

   \(2^5 = 32\).

9. 9

   Why is cancer more common in older people?

   1. AOlder people eat more
   2. BMutations accumulate over time
   3. COlder cells divide faster
   4. DOlder people have no immune system
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   B: Mutations accumulate over time

   Several mutations are usually needed, and they build up over time.