B3: Infection and Response

Question 1

What are pathogens?

Answer 1

microorganisms that cause infectious diseases

Question 2

How can pathogens be spread?

Answer 2

-direct contact
-water or air
-vectors

Question 3

What are vectors?

Answer 3

organisms that carry and pass on the pathogen without getting the disease

Question 4

How can the spread of infectious diseases be reduced?

Answer 4

-simple hygiene measures
-destroying vectors
-isolating infected individuals
-giving people at risk a vaccination

Question 5

What is measles?

Answer 5

a disease caused by a virus:
-symptoms are a fever and a red skin rash
-spread by breathing in droplets from sneezes and coughs
-can be fatal so young children are vaccinated against it

Question 6

What is HIV?

Answer 6

causes AIDS
-spread by sexual contact or exchange of body fluids
-causes a flu-like illness at first
-if untreated the virus enters the lymph nodes and attacks the body’s immune cells
-taking antiviral drugs can delay this happening

Question 7

What is salmonella?

Answer 7

type of food poisoning caused by bacteria
-ingested in food which may not have been cooked properly or may not have been prepared in hygienic conditions
-secrete toxins which cause fever,cramps, vomiting and diarrhoea
-chickens in the UK are vaccinated against it

Question 8

What are protists?

Answer 8

single celled organisms

Question 9

What is malaria?

Answer 9

caused by a protist
-uses a particular type of mosquito as vector
-passed on to a person when they are bitten by the mosquito
-causes sever fevers which reoccurs and can be fatal
-main way to stop it is to stop people being bitten

Question 10

What is rose black spot?

Answer 10

fungal disease
-spread when spores are carried from plant to plant by water or wind
-purple or black spots develop on leaves which often turn yellow and drop early
-loss of leaves stops growth
-treated using fungicides and removing and destroying affected leaves

Question 11

How does mucus help to protect the body against pathogens?

Answer 11

trap particles and bacteria

Question 12

In the stomach, how do glands help to protect against pathogens?

Answer 12

produce hydrochloric acid which kills bacteria in food

Question 13

How do sebaceous glands in the skin help to protect against disease?

Answer 13

produce sebum which kills bacteria and fungi

Question 14

How does the nose help to protect against disease?

Answer 14

traps particles which may contain pathogens

Question 15

What do tears contain that protect against disease?

Answer 15

enzymes that destroy microorganisms

Question 16

How do white blood cells help to defend against pathogens?

Answer 16

through phagocytosis or through the production of antibodies or the production of antitoxins

Question 17

What is phagocytosis?

Answer 17

involves the pathogen being surrounded, engulfed and digested
1. microorganisms invade the body
2. white blood cell finds the microorganisms and engulfs them
3.the white blood cell ingests the microorganism

Question 18

How do antibodies work?

Answer 18

1. antigens are markers on the surface of the microorganism
2. the white blood cells become sensitised to the antigens and produce antibodies
3. the antibodies then lock onto the antigens
4. this causes the microorganisms to clump together, so that other white blood cells can digest them`

Question 19

What is immunity?

Answer 19

the ability to attack a pathogen before it causes disease due to a previous encounter with the pathogen

Question 20

How does vaccination work?

Answer 20

1. a weakened/dead strain of the microorganism is injected. antigens on the surface of the microorganism cause the white blood cells to produce specific antibodies
2. the white blood cells that are capable of quickly producing the specific antibody remain in the blood stream

Question 21

What are antibiotics?

Answer 21

medication used to kill bacterial pathogens inside the body

Question 22

What is MRSA?

Answer 22

a strain of bacteria that is resistant to antibiotics

Question 23

How can bacterial resistance be prevented or reduced?

Answer 23

-doctors should not prescribe antibiotics: unless they are really needed, for non-serious infections, for viral infections
-patients must complete their course of antibiotics so that all bacteria are killed and none of them survive to form resistant strains
-agricultural use of antibiotics should be restricted

Question 24

What is digitalis?

Answer 24

a heart drug that originates from foxgloves

Question 25

What is aspirin?

Answer 25

a pain killer that originates from willow

Question 26

What is penicillin?

Answer 26

an antibiotic extracted from the Penicillium fungus

Question 27

What is a monoclonal antibody?

Answer 27

an antibody produced from a single clone of cells

Question 28

How are monoclonal antibodies used?

Answer 28

-in pregnancy tests
-in labs
-in research
-to treat some diseases

Question 29

How are monoclonal antibodies made?

Answer 29

1. vaccinate a mouse to stimulate the production of antibodies
2. collect spleen cells that form antibodies from the mouse
3. fuse spleen cells and myeloma (tumour cells) to form hybridoma cells
4. grow hybridoma cells in tissue culture and select antibody forming cells
5. collect monoclonal antibodies

Question 30

(there’s 7)

What are signs that a plant may be diseased?

Answer 30

-stunted growth
-spots on leaves
-areas of decay
-growths
-malformed stems or leaves
-discolouration
-presence of pests

Question 31

How can the disease be identified in plants?

Answer 31

-consulting a garden manual or website
-taking infected plants to a lab to identify the pathogen
-using testing kits (which contain monoclonal antibodies)

Question 32

What is tobacco mosaic virus?

Answer 32

a widespread plant pathogen
-infects tobacco plants and many other plants e.g. tomatoes
-produces a distinctive mosaic pattern of discolouration on the leaves which reduces chlorophyll; affecting photosynthesis
-affects growth due to a lack of photosynthesis

Question 33

What are aphids?

Answer 33

small insects that suck food out of the phloem of a plant

Question 34

What physical defences do plants have?

Answer 34

-cellulose cell walls
-tough, waxy cuticle on leaves
-layers of dead cells around stems, which fall off and take pathogens with them

Question 35

What chemical defences do plants have?

Answer 35

-antibacterial chemicals
-poisons to deter herbivores

Question 36

What mechanical adaptations do plants have?

Answer 36

-thorns and hairs to deter animals from eating or touching them
-leaves that droop or curl when touched
-mimicry to trick animals into not eating them or not laying eggs on the leaves