4.1 Communicable diseases, disease prevention, immune system

Question 1

What is a bacteria?

Answer 1

Bacteria are simple organisms classified as prokaryotes. They divide rapidly and cause diseases.

Question 2

What diseases do bacteria cause?

Answer 2

Tuberculosis (TB),
Bacterial meningitis,
Ring rot in potatoes and tomatoes.

Question 3

What are viruses?

Answer 3

Viruses are much smaller than bacteria and not true organisms, as they cannot survive long without a host.

Examples of diseases caused by viruses include AIDS (caused by HIV) and influenza.

Question 4

What diseases do viruses cause?

Answer 4

AIDS (caused by HIV),
Influenza (in many animals),
Infection with tobacco mosaic virus (in plants)

Question 5

What is a protoctista?

Answer 5

A protoctista is a unicellular organism that is eukaryotic and often carried by vectors, such as mosquitoes.

An example of a disease caused by protoctista is malaria.

Question 6

What diseases do protoctista cause?

Answer 6

Protoctista can cause malaria and potato blight/tomato late blight.

Question 7

What are fungi?

Answer 7

Fungi can be unicellular or multicellular. They are a type of eukaryotic cell with a nucleus, organelles, and a chitin cell wall.

Examples of diseases caused by fungi include black sigatoka in bananas and ringworm in cattle.

Question 8

What diseases do fungi cause?

Answer 8

Fungi can cause black sigatoka in bananas, ringworm in cattle, and athlete’s foot in humans.

Question 9

What is direct transmission?

Answer 9

Direct transmission refers to the spread of a disease or infection from one person to another through close contact or physical contact.

Question 10

What is vertical transmission?

Answer 10

Transmission of a disease or infection from parent to offspring.

Question 11

What is horizontal transmission?

Answer 11

Transmission of a pathogen passed between people by touching, kissing or sexual intercourse.

Question 12

What diseases are spread through direct transmission?

Answer 12

HIV, Tuberculosis, Cholera, Anthrax.

Examples: HIV - from mother to child, sexual intercourse or contact with infected blood. Tuberculosis - droplets in the air from coughing and sneezing. Cholera - drinking infected water. Anthrax - travels as spores through the air, spores present in the soil.

Question 13

What is indirect transmission?

Answer 13

Transmission of a disease through an intermediate source, such as contaminated objects or vectors.

Question 14

What diseases are spread through indirect transmission?

Answer 14

Malaria, Lyme disease, Sleeping sickness, Dutch elm disease.

Examples: Malaria - bite from an infected female Anopheles mosquito. Lyme disease - bite from a tick, usually Ixodes ricinus. Sleeping sickness - bite from a tsetse fly (Africa). Dutch elm disease - transmitted by a beetle, Scolytus multistriatus.

Question 15

How do diseases spread?

Answer 15

Warm, cramped, over-populated environments, with poor ventilation and sanitation.

Question 16

What are plant defences?

Answer 16

Cellulose cell walls, lined with waterproof lignin, act as a physical barrier to pathogens. However, plant tissue also contains chemicals to kill any pathogens that try to cross this barrier.

Question 17

What are some primary defences against pathogens?

Answer 17

Stomatal closing, production of chemicals, cellulose deposition, tylose formation.

Question 18

What does stomatal closing do?

Answer 18

Stomata are the small pores on the underside of the leaf. These can close when pathogens are detected.

Question 19

What does the production of chemicals do?

Answer 19

Plants produce many chemicals, such as terpenes, alkaloids, and phenols.

Question 20

What is callose deposition?

Answer 20

This is when the sieve plates in the phloem are blocked with a polysaccharide called callose. This prevents pathogens moving through the phloem and limits the spread of the pathogen.

Question 21

What is tylose formation?

Answer 21

This is when the xylem is blocked from carrying water by a terpene-filled swelling called a tylose. This prevents pathogens moving through the xylem.

Question 22

What are the differences between callose deposition and tylose formation?

Answer 22

A callose deposition occurs in the phloem and a tylose occurs in the xylem. A callose is a blockage caused by polysaccharides and a tylose is a blockage caused by a terpene-filled swelling.

Question 23

What are antibiotics?

Answer 23

Antibiotics are a group of medicines used to treat bacterial infections.

Question 24

What are the benefits of antibiotics?

Answer 24

The first antibiotic was discovered by Alex Fleming, which was Penicillium, in 1928. Since the 1920s, many other antibiotics have been discovered, reaching a peak in the 1980s. Some come from plants and fungi, while others have been made in the laboratory by modifying already known antibiotics. However, fewer new antibiotics have been discovered in the last 2 decades. This is a problem because of the worldwide increase in the antibiotic resistance in bacteria.

Question 25

Why are antibiotics becoming resistant?

Answer 25

Since the first antibiotics were used, some of the bacteria that they killed have become resistant to them. This means that the antibiotic no longer kills them. Some infections have to be treated with a combination of different antibiotics to get around this problem.

Question 26

What are some examples of antibiotic resistant bacteria?

Answer 26

MRSA (methicillin-resistant Staphylococcus aureus) and Clostridium difficile are two types of bacteria that are resistant to most antibiotics and so are very difficult to treat. Outbreaks of these bacteria in hospitals can shut down whole wards; the wards need to be deep cleaned to get rid of the infection.

Question 27

What are the new sources of medicine?

Answer 27

Nature,
Personalised medicine,
Synthetic biology

Question 28

How is nature being used for new medicines?

Answer 28

New medicines are constantly being searched for. Fungi and plants have been good sources of new medicines in the past, e.g. aspirin was found in the bark of the willow tree, current searches are taking place int he rainforests.

Question 29

How is personalised medicine used?

Answer 29

It has been known for some time that not all medicines work for all people. This is likely to be due to genetic differences between people. In the future it is possible that the medicine you are given will be dependent on your genetic profile.

Question 30

How is synthetic biology used?

Answer 30

This is the construction of new biological parts or cells, e.g. developing synthetic bacteria that deliver chemotherapy drugs to cancer cells.