Part 5: Cancer

Question 1

Define tumour. (2)

Answer 1

1. A mass of abnormally growing cells that form when the cells do not respond to the normal mechanisms that control the cell cycle, resulting in uncontrolled cell division/ mitosis.
2. There are two types of tumour: benign and malignant (cancerous and potentially fatal)

Question 2

What happens when a tumour forms?

Answer 2

Tumour cells do not respond to the normal mechanisms that control the cell cycle. They divide rapidly with very little non-dividing time for growth.

Question 3

Name a virus in humans that can cause cancer.

Answer 3

HPV (human papilloma virus)

Question 4

Compare malignant and benign tumours. (5)

Answer 4

1. Malignant tumours can spread around the body, whereas benign tumours can’t.
2. Malignant tumours are referred to as cancer.
3. Malignant tumours invade neighbouring healthy tissues.
4. In benign tumours, the growth of abnormal cells is contained in one place.
5. Malignant and benign tumours can both be life-threatening.

Question 5

State four different causes of cancer.

Answer 5

1. Inherited (genetic)
2. Carcinogenic chemicals
3. Ionising radiation
4. Viruses

Question 6

Explain how genetics can cause cancer.

Answer 6

Certain genes can make you more susceptible to cancer.

Question 7

Explain how carcinogenic chemicals can cause cancer.

Answer 7

Chemicals such as asbestos and tar (from cigarette smoke) can cause mutations in the genetic material.

Question 8

Explain how ionising radiation can cause cancer. (2)

Answer 8

1. The UV radiation can damage skin cells, which can lead to skin cancer.
2. This affects the normal cell cycle because they cause mutations.

Question 9

Explain how viruses can cause cancer. (2)

Answer 9

1. About 15% of human cancers are caused by virus infection.
2. They disrupt the normal cell cycle and can cause cancer.

Question 10

State an example of a cancer caused by genetics.

Answer 10

BRCA genes ——> breast cancer

Question 11

State a cancer caused by carcinogenic chemicals.

Answer 11

Lung cancer

Question 12

State a cancer caused by ionising radiation. (3)

Answer 12

1. Melanoma (a type of skin cancer) appears when there is uncontrolled growth of pigment.
2. Forming cells in the skin
3. As a result of exposure to the UV light from the sun.

Question 13

What is meant by the term ‘mutation’?

Answer 13

Changes in the genetic material.

Question 14

How does ionising radiation damage cells?

Answer 14

1. Ionising radiation penetrates cells, damaging chromosomes and causing mutations in the DNA.
2. These mutations can accumulate over time.

Question 15

Describe the relationship between exposure to ionising radiation and the likelihood of developing cancer.

Answer 15

The more you are exposed to ionising radiation, the more likely it is that mutations will occur and that cancer will develop.

Question 17

Explain how doctors diagnose skin cancer.

Answer 17

Doctors can look for changes in marks on the skin, for example:
• shape
• symmetry
• colour
• size

Question 18

Explain how radiotherapy is used to treat cancer. (3)

Answer 18

1. Radiotherapy occurs when cancer cells are destroyed by targeted doses of radiation.
2. This stops mitosis in the cancer cells but can also damage healthy cells.
3. Methods of delivering different types of radiation in very targeted ways are improving cure rates.

Question 19

Explain how chemotherapy is used to treat cancer.

Answer 19

1. Chemotherapy is where chemicals are used to either stop the cancer cells dividing or make them ‘self-destruct’.
2. There are many types of chemotherapy and scientists are working to make them as specific to cancer cells as possible.

Question 20

Suggest reasons why hair, skin, blood and stomach lining cells are particularly badly affected by the drugs used to treat cancer. (3)

Answer 20

1. Cancer drugs are designed to target rapidly dividing cancer cells.
2. They also tend to affect other rapidly dividing cells.
3. Cells of hair follicles, skin, stomach lining and blood-forming bone marrow are always dividing rapidly.