Topic 3 - Infection And Response

Question 1

What are the 4 pathogens ?

Answer 1

Viruses, bacteria, protists, fungi

Question 2

What are some properties of viruses and how do they work ?

Answer 2

• very small
• they move into cells and use the biochemistry of it to make copies of itself
• this leads to the cell bursting and releasing all the copies in the blood stream
• the damage and destruction of the cells makes the individual feel ill

Question 3

What are the properties of bacteria and how do they work ?

Answer 3

• small
• multiply very quickly through dividing by a process called binary fission
• they produce toxins that can damage cells

Question 4

How do fungi work ?

Answer 4

• they can either be single celled or have a body made up of hyphae
• they can produce spores which can spread to other organisms

Question 5

How can pathogens be spread ?

Answer 5

Direct contact : touching contaminated surfaces
- kissing
- bodily fluids
- skin to skin
- microorganisms from faeces
- infected plant material left in field
Water : drinking or coming in contact with dirty water
Air : pathogens can be carried in the air and then breathed in

Question 6

How can the damage that a disease causes to a population be reduced ?

Answer 6

Improving hygiene :
- hand washing
- disinfectant
- isolating raw meat
- tissues when sneezing
Reducing contact with infected individuals
Removing vectors :
- pesticides/ insecticides
- removing their habitat
Vaccination : by injecting a small amount of a harmless pathogen into an individuals body they can become immune to it so it will not infect them, and can then no longer pass it on

Question 7

What are 3 examples of viral diseases ?

Answer 7

• measles
• HIV
• tobacco mosaic virus

Question 8

What are the symptoms of measles, how is it spread and how can it be prevented ?

Answer 8

Symptoms:
- fever and red skin rash
- can lead to other problems such as pneumonia, encephalitis (brain infection) and blindness
Spread :
- droplet infection
Prevented :
- vaccinations for young children to reduce transmission

Question 9

What are the symptoms of HIV, how is it spread and how can it be prevented ?

Answer 9

Symptoms :
- initially flu like symptoms
- then the virus attacks the immune system and leads to AIDS
Spread :
- sexual contact
- exchange of bodily fluids (blood)
Prevented :
- the spread of: condoms, not sharing needles, screening, bottle feeding
- development of aids : use of antiretroviral drugs

Question 10

What are the symptoms of tobacco mosaic virus, what are the symptoms and how can it be prevented ?

Answer 10

Symptoms :
- discoloration of the leaves
Spread :
- contact between diseased plants and healthy plants
- insects act as vectors
Prevented :
- good field hygiene and pest control
- growing TMV resistant strains

Question 11

What are 2 bacterial diseases ?

Answer 11

• salmonella food poisoning
• gonorrhoea

Question 12

What are the symptoms of salmonella, how is it spread and how can it be prevented ?

Answer 12

Symptoms :
- fever
- stomach cramps
- vomiting and diarrhea
Spread :
- these bacteria can be found in raw meat and eggs
- unhygienic conditions
Prevented :
- poultry vaccinated
- raw meats kept away from cooked foods
- wash hands and surfaces
Cook food thoroughly

Question 13

What are the symptoms of gonorrhoea, how is it spread and how can it be prevented ?

Answer 13

Symptoms :
- thick yellow or green discharge
- pain when urinating
Spread :
- unprotected sexual contact
Prevented :
- contraception, condoms
- antibiotics

Question 14

Give an example of a fungal disease ?

Answer 14

Rose black spot

Question 15

What are the symptoms of rose black spot, how is it spread and how can it be prevented ?

Answer 15

Symptoms:
- purple or black spots on leaves of rose plants
- leaves turn yellow and drop early
Spread :
- spores of the fungus spread in water by wind
Prevented :
- fungicides
-stripping the plant of affected leaves (burning)

Question 16

Give an example of a protist disease?

Answer 16

Malaria

Question 17

What are the symptoms of malaria, how is it spread and how can it be prevented ?

Answer 17

Symptoms :
- fevers and shaking
Spread : the vector is the female Anopheles mosquito, in which protists reproduce sexually. When the mosquito punctures the skin to feed on blood, the protists enter the bloodstream via their saliva
Prevented :
- insecticide coated nets while sleeping
- removing stagnant water
- travelers taking anti malarial drugs to kill parasites that enter the body

Question 18

What are the 4 non-specific defense systems of the body ?

Answer 18

• skin
• nose
• trachea and bronchi
• stomach

Question 19

How does the skin prevent pathogens from entering the body ?

Answer 19

• acts as a physical barrier
• produces antimicrobial secretions to kill pathogens
• good microorganisms (skin flora) compete with the bad ones for space and nutrients

Question 20

How does the nose prevent pathogens from entering the body ?

Answer 20

• has hairs and mucus which prevent particles from entering your lungs

Question 21

How does the trachea and bronchi prevent pathogens from entering the body ?

Answer 21

• secrete mucus in order to trap pathogens
• cilia beat to waft mucus upwards so it can be swallowed

Question 22

How does the stomach prevent pathogens from entering the body ?

Answer 22

• produces Hydrochloric acid which kills any pathogens in your mucus, food or drink

Question 23

What is phagocytosis and how does it protect you ?

Answer 23

• engulfing and consuming pathogens
• this destroys them meaning they can no longer make you feel ill

Question 24

How does producing antibodies protect you ?

Answer 24

• each pathogen has an antigen in their surface which is a structure which a specific complementary antibody can bind to
• once antibodies begin to bind to the pathogen the pathogens start to clump together resulting in it being easier for white blood cells to find them
• if you become infected again with the same pathogen the specific complementary pathogens will be produced at a faster rate, the individual will not feel the symptoms of the illness (they are said to be immune)

Question 25

How do antitoxins work ?

Answer 25

They neutralize the toxins released by the pathogen by binding to them

Question 26

How do vaccines work ?

Answer 26

- they contain a dead or inactive form of the pathogen - this stimulates white blood cells to produce antibodies complementary to the antigens on the pathogen

Question 27

Advantages of vaccination?

Answer 27

- have eradicated many diseases so far (smallpox) and reduced the occurrence of many - epidemics can be prevented through herd immunity

Question 28

Disadvantages of vaccination ?

Answer 28

- they are not always effective in providing immunity - bad reactions can occur in response to vaccines

Question 29

What are antibiotics ?

Answer 29

- medicines that kill bacterial pathogens inside the body without damaging body cells

Question 30

How do bacteria become resistant to antibiotics?

Answer 30

- mutations can occur during reproduction resulting in certain bacteria no longer being killed by antibiotics - when these bacteria are exposed to antibiotics only the non resistant ones die - the resistant bacteria survive and reproduce meaning the population of resistant bacteria increases - therefore antibiotics that were previously effective no longer work

Question 31

How can we prevent the development of antibiotic resistant strains ?

Answer 31

- stop overusing antibiotics as it unnecessarily exposes bacteria to antibiotics - finishing courses of antibiotics to kill all the bacteria

Question 32

What are examples of plants being used in drugs ?

Answer 32

Aspirin , used as a painkiller (willow) Digitalis, used to treat heart problems (foxglove)

Question 33

History of penicillin?

Answer 33

- Alexander Fleming was growing bacteria on plates - he found mould on his culture plates with clear rings around the mould indicating that there was no longer bacteria there - he found out mould was producing a substance called penicillin which killed bacteria

Question 34

What are the different stages of testing new drugs ?

Answer 34

1. Preclinical testing : using cells, tissues and live animals (Clinical = using volunteers and patients) 2. Tested on healthy volunteers with a low dose to ensure there are no harmful side effects 2. Then tested on patients to find the most effective does 3. Then to test how well it works patients are split into 2 groups with one receiving the drug and one receiving a placebo so the effect of the new drug can be observed - these can be single blind (doctor knows) or double blind (neither the doctor or patient knows) 4. Need to be peer reviewed by other scientists to check for repeatability

Question 35

What are monoclonal antibodies?

Answer 35

Identical antibodies that have been produced from the same immune cell and can therefore used to target chemicals and cells in the body as they can only bind to one protein antigen

Question 36

How are monoclonal antibodies produced ?

Answer 36

1. Scientists obtain mice lymphocytes which have been stimulated to produce a specific anitibody 2. They are combined with tumor cells to form a cell called a hybridoma 3. The hybridoma can divide to produce clones of itself which all produce the same antibody 4. The antibodies are collected and purified

Question 37

What are 4 uses of monoclonal antibodies ?

Answer 37

- pregnancy tests - in laboratories to measure and monitor - in research to find or identify certain molecules on a cell or tissue - in treatment of disease ie cancer

Question 38

How do pregnancy tests work ?

Answer 38

1. Pregnancy tests A hormone called human chorionic gonadotrophin (hCG) is present in the urine of women who are pregnant. • There are two sections of the stick. • The first section has mobile antibodies complementary to the hCG hormone- these antibodies are also attached to blue beads. • The second section has stationary antibodies complementary to the hCG hormone which are stuck down to the stick. • The individual urinates on the first section, and if hCG is present it binds to the mobile antibodies attached to blue beads to form hCG/antibody complexes. • They are carried in the flow of liquid to the second section. • The stationary antibodies then bind to the HCG/antibody complexes. • As they are each bound to a blue bead, results in a blue line. • This indicates that you are pregnant.

Question 39

How are monoclonal antibodies used to measure and monitor ?

Answer 39

2. In laboratories to measure and monitor • They can be used to measure and monitor levels of hormones or chemicals in the blood. • The monoclonal antibodies are modified so that they will bind to the molecule you are looking for. • The antibodies are also bound to a fluorescent dye. • If the molecules are in the sample then the antibodies bind to it, and the dye can be observed. • An example is screening donated blood for HIV infections.

Question 40

How are monoclonal antibodies used in the treatment of disease e.g. cancer ?

Answer 40

Cancer cells have antigens on their cell membranes known as tumour markers (not found on normal body cells), which can be targeted. There are three main ways to treat cancers using monoclonal antibodies. a) Producing monoclonal antibodies that bind to the tumour markers in order to stimulate the immune system to attack the cell. b) Using monoclonal antibodies to bind to receptor sites on the cell surface membrane of the cancer cells. This means growth-stimulating molecules cannot bind, stopping the cell from dividing. c) Using monocional antibodies to transport toxic drugs, chemicals or radioactive substances as they can only bind to cancer cells.

Question 41

What are some advantages of using monoclonal antibodies ?

Answer 41

- they only bind to specific cells meaning healthy cells are not affected - they can be engineered to treat many different conditions - we are now able to produce mouse-human hybrid cells to reduce the chance of triggering an immune response

Question 42

What are some disadvantages of using monoclonal antibodies ?

Answer 42

- it is difficult to attach monoclonal antibodies to drugs - they are expensive to develop - as they were produced from mouse lymphocytes they often triggered an immune response when used in humans

Question 43

What are some common signs of plant disease ?

Answer 43

• Stunted growth: indicating nitrate deficiency • Spots on leaves: indicating black spot fungus on roses • Areas of decay: black spot fungus on roses, blights on potatoes • Abnormal growths: crown galls caused by bacterial infection • Malformed stems or leaves: due to aphid infestation • Discolouration: indicating magnesium deficiency, or tobacco mosaic virus • Pests on leaves: such as caterpillars

Question 44

How can you identify the disease a plant has ?

Answer 44

• Using a gardening manual or website • Identifying the pathogen by observing the infected plant in a laboratory • Using monoclonal antibodies in testing its to identify the pathogen

Question 45

What does Nitrate deficiency in plants do ?

Answer 45

- stunts growth - nitrates in the soil convert sugars made in photosynthesis into proteins - these proteins are needed for growth

Question 46

What does magnesium deficiency in plants do ?

Answer 46

- causes chlorosis - magnesium is needed to make chlorophyll (green pigment vital in photosynthesis) - if less is made then parts of the leaves appear green and yellow

Question 47

What are examples of physical defenses in plants ?

Answer 47

- tough waxy cuticle to stop entry of microorganisms in leaves - cellulose cell walls to form a physical barrier into the cells - plants have layers of dead cells around stems (bark) which stop pathogens entering

Question 48

What are examples of chemical defenses in plants ?

Answer 48

Poisons : - foxglove, tobacco plants, deadly nightshade, yew - deter herbivores Antibacterial compounds : - mint - witch hazel

Question 49

What are examples of mechanical defenses in plants?

Answer 49

- thorns and hair make it difficult for animals to eat - some leaves droop or curl when touched to move insects off their leaves Mimicry : - some plants droop to look unhealthy so animals avoid them - plants have patterns to look like butterfly eggs so butterfly’s do not lay their eggs their to avoid competition - species from the ice plant family have a stone and pebble like appearance in order to avoid predation