B3 - Infection And Response

Question 1

What is a communicable disease?

Answer 1

A disease that can spread from person to person.

Question 2

What is a pathogen?

What are the 4 types of pathogens?

Answer 2

A microorganism that causes disease.

All pathogens have antigens (which have a specific shape) on their surface.

4 types of pathogens:
- bacteria
- viruses
- protists
- fungi

Question 3

What is bacteria?

Answer 3

Prokaryotic (no nucleus)
Very small - 1/100th of human cells
Produce toxins

Toxins = chemicals produced by pathogens that make us feel poorly

Question 4

What are viruses?

Answer 4

Not cells & not living
Very tiny - 1/100th of bacteria cells
Enter body cells and reproduce

Question 5

What are protists?

Answer 5

Eukaryotic (have nucleus)
Single celled
E.g. parasites

Question 6

What is fungi?

Answer 6

Eukaryotic
Can be both single celled or multicellular
Have hyphae (thread like structures that can penetrate human skin)

Question 7

How are pathogens spread? Examples?

Answer 7

• through water - e.g. cholera (bacteria)
• through air: breathing in droplets of cough/sneeze - e.g. flu (virus)
• through direct contact: touching surfaces - e.g. athletes foot (fungus)

Question 8

How to reduce / prevent the spread of pathogens? (Non-specific response)

Answer 8

• hygiene (e.g. wash hands)
• destroy vectors (e.g. insecticides)
• isolate infected individuals (quarantine)
• vaccination (cannot develop infection)

Question 9

How does the body prevent pathogens from entering?

Answer 9

• skin = barrier

traps particles:
• hair (nostrils, lashes, etc)
• wax
• mucus

• hydrochloric acid = kills pathogens
• vagina = acidic (hostile environment)
• tears = wash eyeball

Question 10

What type of disease is measles?

Symptoms? and Spread by?

Answer 10

Pathogen: virus

Symptoms:
• fever
• red skin rash

Spread by: inhalation of droplets from sneezes or coughs

Question 11

What type of disease is HIV?

Symptoms? and Spread by?

Answer 11

Pathogen: virus

Symptoms:
• flu like illness
• attacks the body’s immune system (if it is not treated with antiviral drugs)
• in late stage hiv - the body cannot deal with infections or cancer

Spread by: sexual contact & bodily fluids (e.g. blood)

Question 12

What type of disease is tobacco mosaic virus?

Answer 12

Pathogen: virus

Symptoms:
• mosaic pattern of discolouration on the leaves (chloroplasts are infected)
• decreases photosynthesis which reduces growth

Spread by: direct contact

Question 13

What type of disease is rose black spot?

Answer 13

Pathogen: fungus

Symptoms:
• purple or black spots on leaves
• leaves can turn yellow and drop off
• less chlorophyll for photosynthesis = less energy

Spread by: spores from fungus are spread by wind or water

Question 14

What type of disease is malaria?

Answer 14

Pathogen: protist

Symptoms:
• recurrent fever
• shaking when protists burst out of red blood cells

Spread by: mosquito vector

Question 15

What type of disease is salmonella?

Answer 15

Pathogen: bacteria

Symptoms:
• fever
• stomach cramps
• vomiting
• diarrhoea

Spread by: contaminated food

Question 16

What type of disease is gonorrhoea?

Answer 16

Pathogen: bacteria

Symptoms:
• (in early stages) - thick yellow/green discharge from vagina or penis
• pain when urinating

Spread by: sexual contact

Question 17

How does your immune system respond to pathogens?

Answer 17

If a pathogen enters your body, your immune system can attack it.

The main part of your immune system are your white blood cells.

Question 18

What are the 3 main purposes of white blood cells?

Answer 18

1) Phagocytosis: foreign cells are engulfed and digested

2) Produce antitoxins

3) Produce antibodies

Question 19

What are antibodies?

Answer 19

White blood cells produce antibodies to fit onto the antigen.

The pathogens are destroyed by other white blood cells.

Antibodies (proteins) are then produced rapidly and are carried around the body in the blood to find other pathogens.

If a person is infected with the same pathogen, the white blood cells quickly produce the antibodies and you don’t feel poorly. (This is natural immunity)

Question 20

What is a vaccine?

How do vaccines work?

Answer 20

A small amount of dead or inactive pathogen that is injected into your body.

1. The pathogen carries antigens
2. Your body produces antibodies to attack the antigens
3. If you then catch the disease your white blood cells rapidly produce lots of antibodies

Question 21

What are the advantages and disadvantages of vaccines?

Answer 21

Advantages:
• have helped control/eradicate some diseases (e.g. small pox)
• reduce epidemics by slowing the spread of disease

Disadvantages:
• don’t always work
• can cause a bad reaction (e.g. swelling, fever, etc)

Question 22

What are painkillers?

Answer 22

Painkillers
= treat the symptoms of a disease but do not kill the pathogens (e.g. paracetamol)

Question 23

What are antibiotics?

Answer 23

Antibiotics
= kill (prevent the growth of) the bacteria causing the problem without killing your own body cells

• Antibiotics break down the cell walls of bacteria.
• They do not kill viruses because they reproduce inside body cells.

E.g. penicillin

Question 24

How was penicillin discovered?

Answer 24

Discovered by Alexander Fleming in 1928

• He left some petri dishes that were contaminated with mould
• He found that bacteria would not fire near the mould

Question 25

Antibiotic resistance = when antibiotics stop killing the bacteria

How does antibiotic resistance happen?

Answer 25

• bacteria can mutate (change)
• this can cause them to be resistant (not killed by) to an antibiotic
• if you have an infection and treat it with antibiotics only the non-resistant bacteria are killed
• the resistant bacteria are not killed, so they can survive and reproduce

Question 26

How to reduce antibiotics resistance?

Answer 26

• doctors do not over prescribe antibiotics

• patients should complete the course of antibiotics