5. Defending Against Disease

Question 1

What are pathogens?

Answer 1

Microorganism so that cause infectious diseases.

Question 2

What are infectious diseases?

Answer 2

Diseases that can spread easily.

Question 3

What are the two main types of pathogen?

Answer 3

1) Bacteria

2) Viruses

Question 4

What are bacteria?

Answer 4

Very small cells (about 1/100th the size of body cells) which can reproduce rapidly inside the body.

Question 5

How can bacteria make you ill?

Answer 5

1) Damaging body cells

2) Producing toxins

Question 6

Are viruses cells?

Answer 6

No, they are much smaller than that.

Question 7

What are viruses?

Answer 7

Microorganisms much smaller than bacteria (about 1/100th the size of a bacterium).

Question 8

How do viruses make you ill?

Answer 8

They invade your cells and use the cells’ machinery to produce many copies of themselves until the cell bursts and the process repeats. The cell damage makes you feel ill.

Question 9

How does your body defend against diseases?

Answer 9

1) Skin, hair and mucus stop pathogens getting in.
2) Platelets form clots to quickly seal wounds and stop pathogens getting in.
3) Immune system (especially white blood cells) attacks pathogens

Question 10

How do white blood cells defend against pathogens?

Answer 10

1) Engulfing foreign cells and digesting them
2) Producing antibodies
3) Producing antitoxins to counteract toxins produced by invading bacteria

Question 11

What are antigens?

Answer 11

Unique molecules found on the outside of invading cells.

Question 12

What are antibodies?

Answer 12

Proteins produced by white blood cells that can lock onto foreign antigens and kill the pathogens.

Question 13

How do white blood cells use antibodies to fight pathogens?

Answer 13

1) If a foreign antigen is detected, the white blood cells start to produce antibodies to lock onto them and kill the pathogen.
2) Antibodies are then produced rapidly and carried around the body to kill all similar bacteria and viruses.
3) Next time the same pathogen is detected, the body can produce the antibodies far faster.

Question 14

How do vaccinations work?

Answer 14

1) A small amount of a dead or inactive pathogen is injected into a patient.
2) These pathogens still have antigens, which prompts the body to produce antibodies to attack them.
3) The body can store the antibodies.
4) Now if these pathogens ever invade the body, the white blood cells can rapidly produce the right antibody to kill the pathogen.

Question 15

Why are booster injections sometimes needed?

Answer 15

The vaccinations “wear off” over time and booster injections may be needed to increase levels of antibodies again.

Question 16

How can a pathogen be made harmless before it is used in a vaccine?

Answer 16

• Injecting dead pathogens
• Injecting weakened versions of the disease
• Injecting inactive pathogens made harmless through: radiation, heat, chemicals
• Injecting harmless toxins
• Injecting only the antigens

Question 17

How does the MMR vaccine work?

Answer 17

Weakened versions of measles, mumps and rubella are injected into the body.

Question 18

What are the pros of vaccination?

Answer 18

1) Vaccines have helped control lots of infectious diseases that were once common in the UK (e.g. Smallpox no longer exists and polio infections have fallen by 99%)
2) Epidemics can be prevented if a large percentage of a population is vaccinated. Even those not vaccinated are unlikely to get ill because there are few people who they can catch it from.

Question 19

What are the cons of vaccination?

Answer 19

1) Vaccines don’t always work

2) You can get a bad reaction to a vaccine (although this is rare)

Question 20

What is an epidemic?

Answer 20

A large outbreak of disease.

Question 21

What are painkillers?

Answer 21

Drugs that relieve pain. They don’t tackle the cause of the disease, but do reduce symptoms.

Question 22

Give an example of a painkiller.

Answer 22

Aspirin

Question 23

What are antibiotics?

Answer 23

Drugs which kill (or prevent the growth of) the bacteria causing a disease without killing your own cells.

Question 24

Give an example of an antibiotic.

Answer 24

Penicillin

Question 25

Are pathogens diseases?

Answer 25

No, they CAUSE the diseases.

Question 26

Can any antibiotic kill any bacteria?

Answer 26

No, different antibiotics kill different bacteria so you have to be treated by the right one.

Question 27

Do antibiotics destroy viruses?

Answer 27

No

Question 28

Why can’t antibiotics destroy viruses?

Answer 28

Viruses reproduce inside your own body cells, which means the antibiotics cannot reach them without destroying body cells.

Question 29

Give an example of a bacterial disease.

Answer 29

• Salmonella

- Pneumonia

Question 30

Give an example of viral diseases.

Answer 30

• Flu

- Measles

Question 31

How can bacteria become resistant to antibiotics?

Answer 31

1) Bacteria can mutate and sometimes this makes them resistant to an antibiotic.
2) When the antibiotic is used to treat the virus, only the non-resistant bacteria are killed.
3) The resistant bacteria now have space to reproduce and the population of the resistant strain increases.
4) Antibiotics no longer work on this new strain.

Question 32

Give an example of an antibiotic-resist bacteria strain.

Answer 32

MRSA (methicillin-resistant Staphylococcus aureus) causes serious wound infections and is resistant to the powerful antibiotic, methicillin.

Question 33

What are the dangers of antibiotic resistance?

Answer 33

• Bacteria can spread rapidly through a population
• No immunity and no effective treatment
• Risk of epidemic

Question 34

How can the rate of development of antibiotic resistant strains be decreased?

Answer 34

• Doctors have to avoid over-prescribing antibiotics

- Doctors have to avoid using them inappropriately (e.g. Not for only a sore throat)

Question 35

Is antibiotic resistant becoming more of a problem and why?

Answer 35

Yes, because of overuse and inappropriate use of antibiotics.

Question 36

What are superbugs?

Answer 36

Bacteria that are resistant to most known antibiotics.

Question 37

How have drug companies responded to antibiotic resistance?

Answer 37

They have worked on developing new antibiotics which are effective against resistant strains.

Question 38

How can antibiotics be investigated in a lab?

Answer 38

1) A Petri dish is filled with agar jelly.
2) Inoculating loops are used to transfer microorganisms onto the Petri dish. The microorganisms then multiply.
3) Paper disks are soaked in different antibiotics and placed onto the dish. The antibiotics diffuse into the jelly.
4) Resistant bacteria will continue to grow on the agar around a disc, while non-resistant bacteria will die.
5) A dry paper disk is used as a control.
6) The more effective an antibiotic, the larger the clear area around the paper will be.

Question 39

Where can bacteria be grown (cultured)?

Answer 39

In a culture medium. This is usually agar jelly (containing carbohydrates, minerals, proteins and vitamins).

Question 40

At what temperature are bacteria grown in school labs and why?

Answer 40

About 25*C because harmful pathogens are unlikely to grow at this temperature.

Question 41

At what temperature are bacteria grown in industrial conditions and why?

Answer 41

Higher than in school labs be as they grow a lot faster this way.

Question 42

How can contamination be prevented in bacterial experiments (like the one in this chapter)?

Answer 42

1) Petri dish and culture medium must be sterilised before use.
2) Inoculating loop used to transfer bacteria must be sterilised by passing it through a flame.
3) Petri dish should have a lid kept on before bacteria are transferred to culture medium to stop microorganisms from air getting in.
4) While transferring bacteria, lid should only be lifted slightly to stop microorganisms from air getting in.
5) After transferring bacteria, lid should be gently taped on to stop microorganisms from air getting in.
6) Petri dish should be stored upside down to stop bacteria falling onto the agar surface.