Communicable Diseases/Preventing and treating disease COMMUNICABLE DISEASES

Question 1

What are pathogens?

Answer 1

Viruses, fungi, protists and bacteria that spread diseases.

Question 2

Name types of bacteria.

Answer 2

Salmonella - causes food poisoning
Gonorrhoea - STD
Tuberculosis - droplet infection

Question 3

What do bacteria do?

Answer 3

Make toxins that make you feel ill.

Question 4

Name some viruses.

Answer 4

The flue
HIV - causes AIDS (viruses destroy immune system cells)
Measles.

Question 5

What do viruses do?

Answer 5

They invade your cells and reproduce. As they are released they destroy the cells.

Question 6

Name some fungi.

Answer 6

Ringworm
Athletes foot
Thrush

Question 7

Name a protist.

Answer 7

Malaria.

Question 8

Talk about Malaria.

Answer 8

Caused by plasmodium. Carried by a species of mosquito called Anopheles. They are a vector which means they carry the disease without being harmed themselves.
The protists are passed into the human blood streak when bitten. They travel around the human body in the circulatory system. Malaria causes recurrent episodes of fever and shaking when the protist burst out of the blood cells.

Question 9

What are the two types of white blood cell?

Answer 9

Phagocytes
And
Lymphocytes

Question 10

What do phagocytes do?

Answer 10

A type of white blood cell that ingests and digests/destroys the pathogen. They are digestive enzymes.

Question 11

What are lymphocytes?

Answer 11

A type of white blood cell. It makes antibodies to kill pathogens. You need a unique antibody for each type of pathogen.
(they can remember the disease and produce very quickly when infected the second time).

Question 12

What is an antigen?

Answer 12

Proteins on the surface of the cell that cause an immune reaction.

Question 13

What do the cells do after the first infection?

Answer 13

In the first infection the concentration of white blood cells in the body is lower and there is a delay. However, in the second reaction there is a higher concentration of antibodies and there is no delay.
This is because memory cells have been created which kill the pathogen before it has the chance to make you ill.

Question 14

What do vaccination work?

Answer 14

A dead or weakened pathogen is put into the body. This creates memory cells to stop you from being ill if you become infected my the same pathogen. It takes the place of the first infection.
The white blood cells have been stimulated. This means the white blood cells can respond rapidly if they meet the same pathogen again.

Question 15

What are antibodies specific to?

Answer 15

Antigens.

Question 16

Advantages of monoclonal antibodies?

Answer 16

They only bond to the specific diseases or damaged cell that needs treatment. Therefore, healthy cells are not affected at all.
They can be used to treat a wide range of conditions due to their specificity.

Question 17

Limitations of mono global antibodies?

Answer 17

Initially they created more side effects than expected.

Question 18

How are monoclonal antibodies made?

Answer 18

Lymphocytes make antibodies but cannot divide. Rumour cells do not usually make antibodies but they can divide rapidly to make a clone of cells. Scientists combine mice lymphocytes with a type of tumour cell to make a cell called hybridoma. The single hybridoma cell divides to make a large number of identical cells that all produce the same antibodies.

Question 19

What are the uses of monoclonal antibodies?

Answer 19

Pregnancy tests. 
Diagnosis of disease. 
Measuring and monitoring. 
Research. 
Treating disease.

Question 20

What is the first stage of developing a drug?

Answer 20

Testing of cells for toxicity and efficacy (seem to be doing their job).

Question 21

What is the second stage of drug testing?

Answer 21

Testing on animals. This is to find out whether the drug works on a whole living organism. It also gives information about possible dowsed and side effects.

Question 22

What happens after animal testing?

Answer 22

Clinical trials.
To begin it is phase 1 - test for toxicity and tolerated dosage on a small number of healthy volunteers.
Phase 2 - test on patients - use placebo.

Question 23

How does the placebo work in phase 2 trials?

Answer 23

It is a double blind test which means neither the doctors nor the patients know who is receiving the real drug. This ensures the doctors don’t pretend it had worked and so the patients don’t have the placebo effect. This is when the idea of taking medicine makes you fell better.
A group of patients are given sugar pills and another group are given the real drug. Each group must have an equal number of males/females, ages and severity of disease.
Sometimes the patient is given is given a drug that is already used to treat the disease so that they are not deprived of treatment.

Question 24

What happens after the clinical trials of drugs?

Answer 24

After smaller clinical trials the drug is tested on larger groups of people. If the medicine laws all the legal tests it is licensed so that your doctor can prescribe it. It’s safety will be monitored for as long as it is used.

Question 25

Who discovered penicillin?

Answer 25

Alexander Fleming in 1928.

Question 26

How did Alexander Fleming discover penicillin?

Answer 26

He was growing bacteria. He had left the kids off his culture plates and when he returned he found mould growing on them. He noticed a clear ring in the jelly around the mould and realised something had killed the bacteria covering the gel. The mould was called Penicillium.

Question 27

What is penicillin an example of?

Answer 27

An antibiotic.

Question 28

What are the problems associated with antibiotics?

Answer 28

Some strains are resistant.

They only work on bacteria, not viruses.

Question 29

How are pathogens spread?

Answer 29

By air.
Direct contact.
By water.

Question 30

What is bacteria?

Answer 30

A single-celled living organism.

Question 31

What are viruses?

Answer 31

They are even smaller than bacteria. They usually have regular shapes. Viruses cause disease in every type of living organism.

Question 32

What does culture mean?

Answer 32

Grown in very large numbers so the scientist can see all of the bacteria (the colony) as a whole.

Question 33

What is the culture medium?

Answer 33

Giving the bacteria a liquid or gel containing nutrients.

Question 34

What is poured into the Petri dish?

Answer 34

Hot agar gel.

Question 35

How can you sterilise the equipment used to culture microorganisms?

Answer 35

Heat them/use an autoclave.

Question 36

What do you do after you have sterilised the equipment when growing microorganisms?

Answer 36

Inoculate the sterile agar with the microorganisms you want to grow.

Question 37

Why should Petri dishes be stored upside down?

Answer 37

So condensation doesn’t not fall from the lid onto the agar surface.

Question 38

What do you do after inoculating the sterile agar?

Answer 38

They Petri dishes need to be incubated for several days so the microorganisms can grow.

Question 39

In school, what is the maximum temperature at which cultures can be incubated? Why?

Answer 39

25 degrees Celsius. This is to reduce the risk of growing dangerous pathogens.

Question 40

What did Ignaz Semmelweis discover?

Answer 40

He was a doctor in the mid- 1850s. He discovered that many women were dying from childbed fever a few days after giving birth. He noticed that his students were straight from dissecting bodies to delivering babies without washing their hands. The women whose babies that were delivered by doctors were more likely to die than those delivered by midwives. He noticed that a doctor died of a similar disease after cutting himself while operating. He told his students to wash their hands, immediately there were fewer deaths.

Question 41

How can pathogens be prevented from spreading?

Answer 41

Hand washing
Using disinfectants
Coughing or sneezing into a handkerchief.
Keeping raw meat away from food that is eaten uncooked to prevent the spread of pathogens.
Isolating infected patients.
Vaccination.

Question 42

How does your skin act a a defence mechanism?

Answer 42

It produces antimicrobial secretions to destroy pathogenic bacteria.

Question 43

How does your respiratory system act as a defence mechanism?

Answer 43

Nose is full of hairs and produces a sticky liquid called mucus.
Trachea and bronchi secrete mucus.
The stomachs produces acid and this destroys the microorganisms in the mucus you swallow.

Question 44

What are some signs of disease in plants?

Answer 44

Stunted growth
Spots on leaves
Areas of decay or rotting
Growths (eg crown galls caused by bacterial infections)
Discolouration

Question 45

What are the physical barriers of plants?

Answer 45

The cellulose walls help to resist the invasion of microorganisms. Aphids are able to pierce this wall, which breaks the barrier and gives pathogens a way into the cell.
The tough waxy cuticle on the surface of leaves acts as a barrier to the entry of pathogens. (only the stomata that pathogens actually have access to the cells within the leaf)
Bark on trees, and a layer of dead cells on the outside of stems form a protective layer that is hard for the pathogens to penetrate. When the dead cells are lost or shed, the pathogens fall off with them.
Leaf fall - deciduous trees lose their leaves in autumn. Pathogens that could infect the trees fall off with them.

Question 46

What chemical barriers does a leaf have?

Answer 46

Many plants produce antibacterial chemicals that protect them against invading pathogens. Eg mint and witch hazel are often used as mild antiseptics.

Question 47

What is herd immunity?

Answer 47

When a large proportion of the population is immune to a disease, this means that the spread of the pathogen in the population is reduced.

Question 48

What are antibiotics used for?

Answer 48

Drugs to cure bacterial diseases.

Question 49

Give an example of an antibiotic.

Answer 49

Penicillin.

Question 50

How do antibiotics work?

Answer 50

They kill the bacteria that cause disease while they are in your body. They damage the bacterial cells without harming your own cells.

Question 51

What are some problems with antibiotics?

Answer 51

Cannot kill virus pathogens, so they have no effect on diseases caused by viruses. This is because viruses reproduce inside the cells of your body.

Strains of bacteria that are resistant to antibiotics are evolving. This means that antibiotics which are used to kill a particular type of bacteria no longer have an effect., so they cannot cure the disease.

Question 52

What are some bacterial diseases in plants?

Answer 52

agrobacterium tumefaciens - a bacteria that causes crown galls - a mass of unspecialised cells that often grow at the join between the root and the shoot in infected plants. The bacteria inserts plasmids into the plant cells and cause a mass of new undifferentiated genetically modified cells to grow.

Scientists can manipulate the bacteria so that they carry desireable genes into the cells that they infect.

Question 53

What is rose black spot?

Answer 53

A fungal disease of rose leaves. It causes purple of black spots to develop on the leaves. The leaves often turn yellow and drop early. This weakens the plant as it reduces the area available for photosynthesis.

The spores of the fungus are spread in the environment, carried by the wind. They are then spread over the plant after it rains in drips of water that splash from one leaf or plant to another.
The spores stay dormant in winter on dead leaves and on the stems of rose plants.

Question 54

How is rose black spot spread?

Answer 54

The spores of the fungus are spread in the environment, carried by the wind. They are then spread over the plant after it rains in drips of water that splash from one leaf or plant to another.
The spores stay dormant in winter on dead leaves and on the stems of rose plants.

Question 55

How do farmers try to prevent rose black spot from spreading?

Answer 55

Burning affected leaves and stems. Chemical fungicides can also help to treat diseases and prevent it spreading.
Horticulturists have bred types of roses that are relatively resistant to black spot but the disease still cannot be prevented or cured.

Question 56

What are anti-toxins?

Answer 56

Some white blood cells produce antitoxins. These counteract (cancel out) the toxins released by pathogens.

Question 57

What are aphids?

Answer 57

They have sharp mouthparts that penetrate into the phloem vessels of the plant so they can feed on the sugar-rich phloem sap. They attack in large numbers, depriving the plant cells of the products of photosynthesis. This can damage and weaken the plant. They can also act as vectors, transferring viruses, bacteria, and fungi from diseased plants into the tissues of healthy plants on their mouthparts.

Question 58

How can aphids be destroyed?

Answer 58

Chemical pesticides, or in enclosed spaces such as greenhouses, using biological pest control. Releasing aphid-eating insects such as ladybirds and their larvae can control the pathogen population so it does not have an impact on the success of the crop.

Question 59

What are some signs of diseases in plants?

Answer 59

stunted growth
spots on leaves 
areas of decay or rotting 
growths
malformed stems or leaves 
discoloration 
presence of visible pests.

Question 60

What is cholorosis?

Answer 60

The yellowing of leaves due to low magnesium levels in the soil. Low magnesium ions in the soil means that the plant cannot make enough chlorophyll. The plant becomes yellow and growth slows down because the plant cannot photosynthesise fully.

Question 61

What is a sign of nitrate deficiancy?

Answer 61

Stunted growth.

Question 62

What is a sign of magnesium deficiency?

Answer 62

Discolouration.

Question 63

How do plants defend themselves against herbivores?

Answer 63

poison eg foxgloves
thorns eg cacti
hairy stems eg nettles
drooping or curling when touched eg mimosa pudica
mimicry - drooping to mimic unhealthy plants which tricks animals into not eating them. Some mimic butterfly eggs on their surface so butterflies don’t lay their eggs on the plant, to avoid competition with caterpillars.