SB5 - Health, Disease, and the Development of Medicines

Question 1

SB5a
1) Define the term health.
2) Define the term disease.
3) Describe how communicable and non-communicable diseases differ

Answer 1

1) Health is a state of complete physical, mental and social well-being.
2) Diseases are illnesses that affect an organism’s body, organs, tissues or cells.
3) Communicable diseases can be transferred from one person to another, or from one organism to another.
Non-communicable diseases are not transferred between people or other organisms.

Question 2

SB5a
1) Outline the role of the immune system in protecting against disease
2) Explain how disease can affect the immune system
3) Define risk factor

Answer 2

1) The immune system protects the body from pathogens. If a pathogen gets past the first line of defence (the non-specific defences), the immune system works to stop or minimise infection.
2) A disease can damage the immune system, which makes it easier for other pathogens to cause disease.
3) A risk factor is a factor associated with an increased likelihood of getting a disease.

Question 3

SB5b
1) Give examples of non-communicable diseases.
2) Define the term malnutrition.
3) Explain how diet can lead to malnutrition.

Answer 3

1) Non-communicable diseases include: cancer, diabetes, genetic diseases and conditions, and heart disease.
2) Malnutrition occurs when you get too little or too much of particular nutrients from your food.
3) A poor diet can mean that you are consuming a lack or too much of certain nutrients, which leads to malnutrition.

Question 4

SB5b
1) Describe the link between alcohol and liver disease.
2) Explain the effect of alcohol consumption and obesity at local, national and global levels.

Answer 4

1) When alcohol is broken down by the liver, toxic products are released. Too many of these toxic products can cause permanent liver damage.
2) - Obesity and alcohol consumption are risk factors for other non-communicable diseases. For example obesity can result in type 2 diabetes, and alcohol can result in liver disease.
- More diseases results in more pressure on the resources of local hospitals and the NHS as a whole to treat people with obesity and related health issues.
- More disease means that less people in society will be able to work and contribute to the economy.
- Alcoholism also increases violence, antisocial behaviour and accidents, as well as increasing treatment costs to the NHS

Question 5

SB5c
1) Describe the two ways in which obesity is measured, and what are the formulae?
2) Describe how obesity correlates with cardiovascular disease
3) Describe how smoking correlates with cardiovascular disease
4) Why may BMI be misleading when assessing the risk of developing obesity-related disorders?

Answer 5

1) BMI stands for body mass index, and predicts the amount of fat in the body. If your BMI is 30 or above, you are obese.
The formula for BMI is weight (kg) / (height (m) squared)
Waist to hip ratio (WHR) is used by dividing the waist measurement by the hip measurement.
2) Obesity leads to high blood pressure and the build-up of fatty deposits in the arteries, which lead to cardiovascular disease. Therefore, being obese is a risk factor for cardiovascular disease.
3) Tobacco smoke contains many harmful substances that damage the artery lining. This causes fat to build up at the site of damage, making the artery narrower. Therefore, a blood clot may block the artery here, or break off and block an artery in another part of the body, causing a heart attack or stroke.
4) A person’s body mass may be high in relation to their height because they have a lot of muscle rather than fat. This would mean that they have a high BMI but are not likely to be at risk of developing obesity-related disorders.

Question 6

SB5c
1) Explain why exercise and diet affect obesity.
2) Compare how cardiovascular diseases are treated (medication, stents, and heart transplants)

Answer 6

1) A poor diet and lack of exercise can lead to obesity. This is because eating too much saturated fat and not burning the fat through exercise can can cause fat to build up below the skin and around the organs, which causes obesity.
2) Medication: Statins are drugs that help to lower cholesterol in the blood.
Anticoagulants make blood clots less likely.
Stents: Coronary arteries that are blocked or have become narrow can be stretched open and a stent inserted to maintain blood flow to the heart.
The benefits that are surgery is quick and the stents can last a long time. The issues are that surgery has risks, such as the risk of infection to bleeding, and a blood clot can occur near the stent.
Heart transplants: A heart transplant is required in cases of heart failure. Coronary heart disease can lead to heart failure. This is where heart fails to pump sufficient blood and organs are starved of oxygen.
The issues are that trying to find a new human biological heart takes a long time, and the heart could be rejected.
Artificial hearts don’t work very well and are only temporary. However, a benefit is that they can’t get rejected.

Question 7

SB5d
Explain how signs of a disease can be used to identify the pathogen

Answer 7

The process to identify a disease may include the following steps:
1) Following a report of a possible infection, scientists will visit the location.
2) To avoid any confusion it is essential they look at other factors that might cause similar symptoms. For example, damage to leaves might be caused by a pathogen or grazing animals.
3) The scientists will try to identify any environmental causes such as pollution that might be affecting the plants.
4) Finally they will photograph the symptoms and take samples for laboratory analysis.

Question 8

SB5e
1) State the ways in which pathogens can be spread.
2) Explain how the spread of different pathogens can be reduced or prevented in 4 different ways of spreading

Answer 8

1) The ways that pathogens are spread: direct contact, air, water, vector, unprotected sexual activities and bodily fluids.
2) Water: prevented by good hygiene, boiling water before use, treating water chemically to kill bacteria, and only drinking bottled water.
Direct contact, air: keep infected people separated from others; cut down and burn infected trees, or maybe restrict the import of ash trees to prevent any infected trees entering the country
Unprotected sexual activities and bodily fluids: use a condom, don’t share needles because there is a risk of injecting bodily fluids from the previous user of the needle.
Vector (eg. Mosquitoes): Sleep under mosquito net, spraying standing water with insecticides to kill the vector.

Question 9

SB5f
1) Describe the structure of a virus.
2) Explain how viruses differ from cells.
3) Describe the lytic pathway of a virus life cycle

Answer 9

1) They contain one or more strands of genetic material surrounded by a protein coat called a capsid.
2) Viruses cannot replicate on their own like other cells; they need to invade a host cell and use their cell components to make new virus cells. They cannot replicate on their own because they don’t have the components/ proteins and enzymes necessary to reproduce by themselves.
3) A. The virus injects its genetic material into the host cell
B. It then uses proteins and enzymes in the host cell to replicate its genetic material and produce components of new viruses.
C. The viral components then assemble into new viruses.
D. Then, the host cell splits open releasing new viruses, and other nearby cells can then be infected with the virus.

Question 10

SB5f
1) Describe the lysogenic pathway of a virus life cycle.
2) Compare and contrast the lytic and lysogenic pathways.
3) How do you calculate the cross-sectional area of viral cultures and clear agar jelly?

Answer 10

1) The lysogenic cycle: The virus injects its DNA into the host cell and the DNA becomes incorporated into the host DNA
As the host cell replicates, the viral DNA replicates also, but no new virus particles are made during this time (the virus is dormant).
An environmental change acts as a trigger for the viral DNA to exit the genome of the host. Then the viral DNA enters the lytic cycle so the proteins of the host cell are used to make new components of the virus.
2) In the lytic cycle, the viruses infect the host cell and uses its metabolism to multiply, causing the lysis or death of the cell. Whereas, the lysogenic cycle consists of a virus that lies dormant, and the host cell is reproducing instead.
3) Formula: cross sectional area = πr²
You measure to the centre of the cross-sectional area.

Question 11

SB5g
1) Describe 2 physical barriers of plants to pests and pathogens.
2) Describe some chemical defences of plants to pests and pathogens.
3) Describe how plant protective chemicals are used to treat human diseases or symptoms.

Answer 11

1) Physical barriers stop pathogens from entering and damaging an organism. They include: the waxy cuticle of leaves, and layers of dead cells (eg. the bark on stems).
2) Plants produce chemical substances such as poisons or insect repellents. They either kill some pathogens, or deter pests from feeding on their leaves.
3) Aspirin used as pain relief comes from an acid produced by willow trees.

Question 12

SB5g
1) Describe examples of aseptic technique.
2) Explain why aseptic technique is used during the culture of microorganisms.

Answer 12

1) Using autoclaves to sterilise equipment and growth medium (eg. flaming the necks of bottles)
2) Tests on bacterial and human cells need to avoid contamination by other microorganisms in the air. Aseptic techniques help to avoid this. Contamination will affect the results of the experiment.

Question 13

SB5h
1) Describe how plant diseases are detected using visible symptoms.
2) Describe how environmental causes of plant problems are eliminated when identifying disease.

Answer 13

1) The visible symptoms can be matched to a gardening manual, and used to identify the cause of the disease.
2) Eliminating possible environmental causes – a plant may be showing symptoms due to deficiencies in the environment for example, lack of nutrients. If a nutrient deficiency is suspected, the nutrients can be added to the soils of the affected pants, and observe whether or not the symptoms disappear. By changing the environment and supplying the plant with the nutrients, you can identify whether the symptoms were due to the lacking nutrients or if they were because of a specific disease.

Question 14

SB5h
1) Describe how distribution analysis can help identify a plant disease.
2) Describe how plant pathogens are diagnosed in the lab.

Answer 14

1) Different pathogens disperse in different ways, so the distribution of the infected plants may indicate what method of dispersal is used by the pathogen. Patches of diseased plants may suggest infection through the soil, while random distributions may suggest airborne transmission.
2) Monoclonal antibodies that are complimentary to the antigens on the bacteria are added to the infected plant tissue sample in the diagnostic test. These are antibodies that are specific to the antigens on the pathogen. If the antigen is present in the infected plant sample, the antibodies will bind to them and allow accurate diagnosis of the disease.

Question 15

SB5i
1) Explain how the spread of the STIs Chlamydia and HIV can be reduced or prevented.
2) Why may a person be symptomless for a long time after the initial period of infection by HIV?
3) Explain why a person with AIDS become seriously ill due to infection by another pathogen

Answer 15

1) Chlamydia is a disease caused by bacteria that may result in infertility. Chlamaydia is transmitted by bodily fluids. Therefore, using a condom prevents the mixing of bodily fluids during sexual intercourse. HIV is a virus that eventually leads to a disease called AIDS in the people it infects. They are most commonly spread by sexual contact, and a method to prevent it spreading is using a condom during sex.
2) After entering cells, HIV enters the lysogenic stage of its life cycle and becomes dormant. Therefore, the virus is not active and will not be causing any symptoms in the infected person.
3) HIV kills white blood cells, which are an important part of the immune response, so the immune system is weakened. This means that the person is more vulnerable to infection by other pathogens.

Question 16

SB5i
1) Describe how physical barriers protect the body
2) Describe how chemical barriers protect the body
3) What is meant by a ‘specific immune response’?

Answer 16

1) The skin covers almost all parts of your body to prevent infection from pathogens. If it is cut or grazed it immediately begins to heal itself, often by forming a scab, which prevents infection as the skin acts as a physical barrier.
The nose has internal hairs, which act as a physical barrier to infection. Cells in the nose produce mucus. This traps pathogens before they can enter the lungs. When the nose is blown, mucus is removed and any pathogens are trapped within it.
The lungs: The cells that line the trachea also have hairs called cilia, which are much smaller than those in the nose. These are called ciliated cells. The ciliated cells waft their hairs in a motion like a Mexican wave at a football match and move mucus and pathogens upwards towards the throat where it is swallowed into your stomach. Other cells called goblet cells create the mucus in order to trap pathogens. The production of mucus in your airways is a physical barrier.
2) The eyes produce tears which contain enzymes called lysosomes. This kills bacteria on the surface of the eye.
The hydrochloric acid in the stomach kills pathogens that reach the stomach.
3) A ‘specific immune response’ is the immune response to a specific pathogens.

Question 17

SB5j
1) What is the role of the immune system?
2) What does it mean if a person is immune to a disease?
2) Describe how antigens trigger the release of antibodies and the production of memory lymphocytes, including how it looks on the graph
3) Describe the role of antibodies in the immune response.

Answer 17

1) The immune system protects the body by attacking pathogens.
2) The immune system can respond quickly if the pathogen which causes the disease enters their body again.
3) The first exposure to the pathogen is shown on the graph right before the antibodies are produced and the graph line goes up. Lymphocytes bind to antigens and produce specific complementary antibodies. Then, the antibodies defend against pathogens. They bind on the pathogen’s antigen and directly destroy them. Lymphocytes can also produce antitoxins. These antitoxins can also neutralise the toxins released by the pathogen. Memory lymphocyte production is also triggered. The point when it is produced is show on the graph after the first pathogen exposure by a horizontal, dashed line. At the time of second exposure (right before the second curve) the body has some memory lymphocytes that will recognise the pathogen’s antigens, and trigger more antibodies to be made. This means antibodies will be produced much more quickly (shown by a steeper curve) following the exposure, and the curve will be steeper.
4) Antibodies are produced by the lymphocytes to target and neutralize pathogens and toxins. They recognize and bind to the complementary antigens on specific pathogens so that they can be destroyed.

Question 18

SB5j
1) Describe the role of memory lymphocytes in triggering a secondary response.
2) Explain how immunisation protects against infection by a pathogen.
3) Discuss advantages and disadvantages of immunisation

Answer 18

1) Memory lymphocytes (also known as B-lymphocytes) detect antigens on a pathogen in the blood. B-lymphocytes produce specific antibodies, which lock onto the pathogen and destroy it. The antibodies are produced rapidly and flow throughout the body to find all similar pathogens.
2) - A weakened form of a pathogen which cannot cause disease is injected into someone.
- This causes lymphocytes to make and then release complementary antibodies to attack and kill the specific antigen that was injected.
- Some memory lymphocytes remain in the bloodstream which can produce the specific antibody for the antigen.
- If the body is infected by the real pathogen, the memory lymphocytes will release antibodies to fight off the pathogen and quickly destroy it.
3) Advantages of immunisation:
- Less likely to get a disease from a pathogen
- Develop herd immunity, which keeps vulnerable unvaccinated individuals safe
- Possibly eradicate the pathogen
- Vaccination is cheaper than treating a sick patient.
Disadvantages of immunisation:
- Possible side effects
- Poor vaccine distribution, not everyone can receive or afford it
- Low vaccination rates within certain groups due to religious and ethical reasons

Question 19

SB5l
1) Define the term monoclonal antibody.
2) Define the term hybridoma cell.
3) Describe how monoclonal antibodies are produced by lymphocytes.

Answer 19

1) Monoclonal antibodies are identical copies of one type of antibody. They are specific to one type of antigen, and engineered by scientists.
2) A hybridoma cell is a cell where lymphocytes are combined with a particular type of tumour cell.
3)- An antigen is injected into a mouse. (Scientists must first inject the animal with an antigen so that the animal makes B-lymphocytes which produces antibodies that are complementary to the antigen that’s injected.)
- The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen.
- Spleen cells which produce the lymphocytes are removed during a small operation.
- The spleen cells are fused with human cancerous white blood cells called myeloma cells to form hybridoma cells which divide indefinitely. (Tumour cells are used because tumor cells divide rapidly, so using them means the hybridoma cell will divide rapidly to produce many clones, which can produce more of the monoclonal antibodies.)
- These hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen.

Question 20

SB5l
1) Explain how monoclonal antibodies are used in pregnancy testing.
2) Explain how monoclonal antibodies are used in diagnosis of disease (including blood clots and cancer).
3) Explain the advantages of monoclonal antibodies compared with drug and radiotherapy treatments to target cells.

Answer 20

1) During pregnancy, a woman begins to produce hCG hormone, which becomes present in her urine. To use the test, the woman should urinate on the patch containing the blue beads. If hCG is present in her urine, then the monoclonal antibodies on the blue beads will attach to the hormone. The urine carries the beads and the hormone to the test strip, where they bind to the antibodies secured on the strip. The test strip will then turn blue, showing a positive result.
2) Cancer: When injected into a person’s body, the monoclonal antibodies will bind with these cancer cells and clump them together. This makes it easier to identify a cancerous tumour , which can then be treated or removed.
The monoclonal antibodies are also used in the diagnosis of the cancer. The antibodies are made slightly radioactive. The antibodies then attach to the cancer cells and then radiation can be detected using a PET scanner, for example.
Blood clots: Monoclonal antibodies have been developed that bind to the proteins which form blood clots. These antibodies can be labelled with a radioactive element and injected into the bloodstream. A camera which detects radiation can then be used to visualise where the antibodies have accumulated, and so the position of any blood clots.
3) Monoclonal antibodies allow the specific targeting of drugs to cancer cells. This means that fewer body cells are affected compared with normal drug and radiotherapy treatments, so there are fewer side effects.

Question 21

SB5k
1) Define the term antibiotic
2) Explain why antibiotics are useful for treating bacterial infections
3) Explain why antibiotics cannot be used to treat infections by pathogens other than bacteria.

Answer 21

1) Antibiotics are substances that slow down or stop the growth of bacteria.
2) Antibiotics kill or prevent the growth of bacterial cells but they do not harm human cells.
3) Antibiotics are designed to kill only bacteria, not other pathogens. Viruses can only reproduce inside their host’s cells. This means that it is very hard to develop drugs which target the virus but not the cells of the host.

Question 22

SB5k
1) Describe the stages of development of new medicines.
2) What are the three things which are investigated during the preclinical testing of drugs?
3) Why are very low doses of the drug given at the start of clinical trials?

Answer 22

1) Preclinical drug trials (stage 1): The drugs are tested using computer models and human cells grown in the laboratory.
Animal trials (stage 2): Drugs that pass the first stage are tested on animals.
Human clinical trials (stage 3): Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check that they are safe. If this is successful, they will test it on a small amount of patients who the drug was produced for.
2) Toxicity: how harmful the drug is (side effects)
Efficacy: how well the drug works (effectiveness)
Dosage: how much of the drug is given
3) Low doses of the drug are used initially in case the drug has any harmful effects. If this is safe the dosage increases until the optimum dosage is identified.

Question 23

SB5k
1) What are blind and double-blind trials?
2) What are placebos?
3) Define preclinical

Answer 23

1) In blind trials, the doctor knows which patients have been given the drug and which have been given the placebo, but the patients do not know.
In double blind trials, neither the doctor nor the patient knows who has been given the drug or placebo. This ensures that neither the patients nor the doctors are able to subconsciously influence the results of the trials.
2) A placebo is an inactive substance that looks like the drug but does not do anything.
3) Preclinical is the stages of drug testing before testing the drug on a human. The drug is tested on human cells and animals.

Question 24

SB5j
1) Why is an immunised person less likely to develop a disease?
2) Why might a person get vaccinated before travelling to another country?
3) What are the two types of white blood cells?
4) Explain herd immunity

Answer 24

1) The person would respond to the vaccine by producing antibodies and memory lymphocytes. Because of this, if the pathogen enters their body again, their immune system will recognise the foreign antigens and respond more quickly, meaning they will be more likely to eradicate the pathogen before it causes the disease.
2) To prevent bringing diseases to the country that they are travelling to, to prevent getting a disease while in the country, and to prevent bringing a disease back to their own country.
3) There are two types of white blood cell called phagocytes and lymphocytes. Phagocytes surround any pathogens in the blood and engulf them. Lymphocytes produce antibodies which kill the pathogens, and antitoxins which neutralise the effect of the pathogen’s toxins.
4) If many people in a population are immunised, then there will be fewer people who are likely to catch the disease and pass it on to others. This is herd immunity. This means that even is some individuals cannot be immunised, they are less likely to come into contact with someone with the disease and so are less likely to catch it.

Question 25

Core Practical - SB5k
1) What is the aim for the antibiotics core practical?
2) What are the steps for the antibiotics core practical?

Answer 25

1) Investigate the effects of antiseptics, antibiotics or plant extracts on microbial cultures.
2) Stage 1
A) Use aseptic technique to pour an agar plate. Make sure the base of the Petri dish is covered with agar and the surface of the agar is smooth.
B) When the agar has set, remove a sterile pipette from its wrapper. Do not put this down.
C) With your left hand pick up the bottle of bacterial culture. Place its cap in the palm of your right hand, and curl the little finger of your right hand around the cap. Then twist the cap off, keeping hold of it.
D) Pass the neck of the bottle through a Bunsen flame, insert the pipette into the culture and draw up a very small amount of the culture.
E) Pass the neck of the bottle through the Bunsen flame again, and screw the cap back on.
F) Lift the lid of the Petri dish a small way, and gently add a couple of drops of culture to the agar. Replace the lid. Place the pipette in disinfectant.
G) Unwrap a sterile spreader. Lift the lid of the Petri dish a small way, and then spread the drops of the culture across the agar using a side-to- side motion with the spreader. Replace the lid. Place the spreader in disinfectant.
Stage 2
H) Mark the bottom of the dish in sections. Label one section for each concentration of the antibiotic you will use and one for the control. Place the dish the right way up on the bench.
I) Sterilise the forceps and use them to place a sterile filter paper disc in the ‘control’ section of the dish.
J) Re-sterilise the forceps, then use them to place one antibiotic disc in the correct section of the dish.
K) Repeat step J for the other antibiotic discs.
L) Tape the lid onto the dish to stop the lids from falling off and unwanted microorganisms entering, and turn the dish upside down to stop moisture from dripping down onto the bacteria and disrupting the colonies. Give the dish to your teacher for incubation. Wash your hands thoroughly.
Stage 3
M) Measure the diameter of the clear space around each disc. Work out the radius and use this to calculate the cross-sectional area of each space.
N) Draw a graph showing cross-sectional area against concentration of antibiotic.

Question 26

Core Practical - SB5k
1) Explain the clear areas on a petri discs, and suggest why some antibiotics do not have clear areas in the antibiotics core practical
2) Give 3 aseptic techniques that should be used when preparing an agar plate so that it does not become comtaminated
3) Give 2 aseptic techniques that should be used when spreading the bacteria
4) Why might it be difficult to test the effects of different antiseptics on a plate where the bacteria is merged together instead of separate spots?

Answer 26

1) The clear zones are called the zones of inhibition.
The clear areas occur because the antibiotic diffuses out from the paper disc into the surrounding medium. If the bacteria are affected by the antibiotic, they die and leave a clear space.
If there are no clear areas around the antibiotic, this means that bacteria are resistant to the antibiotic, so the antibiotic doesn’t kill the bacteria to create an inhibition zone.
If the antibiotic is usually effective, but there are are no clear areas or the clear area is smaller, then it could be an anomalous result, or not enough antibiotic was used.
2) a. Use a autoclave to sterilise the Petri dish and the agar before using them
b. Keep the Petri dish covered while it is drying/ keep the lid on the agar plate after growth
c. Work close to a Bunsen Burner flame to kill pathogens in the air
3) a. Pass the inoculating loop through a hot Bunsen burner flame before using it to sterilise it
b. Only remove the lid of the culture vial very briefly when transferring the bacteria
4) The bacteria has not been evenly spread across the agar so if would be very difficult to calculate the size of inhibition zones around different antiseptics on the plate.

Question 27

Core practical - SB5k
1) What are the safety isssues for the antibiotics core practical?
2) How would the forceps and control filter paper disc be sterilised and why?
3) Why are the tapered dishes kept in a warm place/ at a certain temperature?

Answer 27

1) The disinfectant is flammable, so keep it away from naked flames. The naked flames could cause burns, so be careful around the Bunsen burner.
2) Suitable suggestions (which will depend on how this has been done in class) include: wrapping the forceps and control filter disc in foil and placing in an autoclave/pressure cooker; dipping the forceps in an ethanol solution and the flaming them; leaving the forceps in disinfectant solution for a set length of time.
Sterilising the forceps at each stage reduces the risk of infection of the culture with other microorganisms, which could affect results.
3) Bacteria grow faster in warm conditions. Keeping the plates at a certain temperature provide optimal growth conditions.

Question 28

Core practical - SB5k
1) What is the purpose of the control disk?
2) How would you obtain more accurately measurements for the radius of a clear space?
3) What variables need to be controlled during the test?

Answer 28

1) The disc contains no antibiotic and so will show that any clear area around other discs is the effect of the antibiotic and not something else in the disc.
2) Use a ruler that has millimetre divisions.
3) The control variables include:
- The volume of antiseptic
- The incubation temperature
- The same type of agar
- The amount of bacteria

Question 29

SB5c
Compare the advances and disadvantages of a lifestyle change vs surgery (such as stents and a heart bypass) as treatment for coronary heart disease

Answer 29

A lifestyle change is cheaper than a heart bypass or stent as surgery can be expensive.
A lifestyle change has less risks than a heart bypass of stent, as it does not require surgery.
However, the impact is not immediate, the patient may find it difficult and may not have the will power, and it is not an option in a medical emergency such as a heart attack.

Question 30

SB5k - Core Practical
1) Explain why aseptic precautions are used
2) Why are agar plates usually incubated with the surface of the agar facing downwards?

Answer 30

1) Aseptic precautions are used so only the desired bacteria are transferred to the spreader, and no unwanted microorganisms are spread to the agar plate. Using aseptic techniques kills the microorganisms on the spreader.
2) So condensation doesn’t run down on to agar and to avoid contamination.

Question 31

SB5k - Core Practical
1) Describe how you could tell if a nutrient plate was contaminated with other organisms
2) Explain why you should not create an airtight seal when taping the lid to the Petri dish

Answer 31

1) There would be different coloured colonies visible.
2) To make sure anaerobic bacteria don’t grow, as anaerobic bacteria can be pathogens.

Question 32

SB5d
State the type of disease, how the disease is spread and the symptoms for the following diseases:
1) Cholera
2) Chalara dieback
3) Ebola

Answer 32

1) Cholera: bacterial disease, is spread as a waterborne disease, causes watery diarrhoea and dehydration.
2) Chalara dieback (affects ash trees only): spread by wind, causes wilting in the branches and tree death.
3) Haemorrhagic fever (Ebola): Viral disease, spread by contact with bodily fluids, causes high fever, vomiting, and aches and pains.

Question 33

SB5d
State the type of disease, how the disease is spread and the symptoms for the following diseases:
1) Malaria
2) Tuberculosis

Answer 33

1) Malaria: Vector disease, spread by mosquitoes, causes high fever, vomiting and death
2) Tuberculosis: Bacterial disease, airborne, causes coughing up blood and weight loss

Question 34

SB5d
State the type of disease, how the disease is spread and the symptoms for the following diseases:
1) AIDS
2) Stomach Ulcers

Answer 34

1) AIDS: Viral disease, spread by unprotected sexual activities, causes a weak immune system and death
2) Stomach Ulcers: Bacterial disease, spread by saliva or vomit, causes a stomach lining attack