Topic 5 - Health, disease and the development of medicines

Question 1

Describe health as WHO defines it

Answer 1

A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity, as defined by the World Health Organization (WHO)

Question 2

Compare communicable and non-communicable diseases.

Answer 2

Communicable diseases can be transferred between individuals. They are caused by a pathogen.

Non-communicable diseases cannot be transferred between individuals.

Question 3

Explain why the presence of one disease can lead to a higher susceptibility to other diseases

Answer 3

A disease can damage the immune system (e.g. HIV) or the body’s natural defences, making it easier for pathogens to enter the body or it can cause organ systems to stop working well.

Question 4

Describe a pathogen

Answer 4

A disease-causing organism, including viruses, bacteria, fungi and protists

Question 5

Describe cholera

Answer 5

A type of bacteria which is spread by water and causes diarrhoea

Question 6

Describe Chalara ash dieback

Answer 6

A type of fungi which is airborne and causes leaf loss and bark lesions in plants

Question 7

Describe tuberculosis

Answer 7

A type of bacteria which is airborne and causes lung damage and coughing

Question 8

Describe malaria

Answer 8

A type of protist which is spread by the animal vector of mosquitos and causes damage to blood and the liver

Question 9

Descrive HIV

Answer 9

A virus which is spread by body fluids that destroys white blood cells, leading to the onset of AIDs

Question 10

Describe Helicobacter

Answer 10

A bacteria which is spread via oral transmission that can lead to stomach ulcers

Question 11

Describe Ebola

Answer 11

A virus which is spread by body fluids that causes hemorrhagic fever (a fever accompanied by sever bleeding).

Question 12

How can the spread of pathogens be reduced or prevented?

Answer 12

• Improving hygiene - hand washing, using disinfectants, isolating raw meat, using tissues and handkerchiefs when sneezing
• Reducing contact with infected individuals
• Removing vectors - Using pesticides or insecticides and removing their habitat
• Vaccination - injecting a small amount of a harmless pathogen into an individuals body, they can become immune to it so it will not infect them. This means they cannot pass it on to other individuals.

Question 12

What ways can pathogens be spread?

Answer 12

• By direct contact - touching contaminated surfaces e.g. kissing, contact with bodily fluids, skin to skin
• By water - drinking or coming in to contact with dirty water
• By air - pathogens can be carried into the air and breathed in e.g. droplet infection when sneezing, coughing or talking expels pathogens in droplets which can be breathed in.

Question 12

Describe the lyctic pathway

Answer 12

Viruses can ‘survive’ outside of a host but they require host cells to reproduce. One way this can be done is throught the lyctic pathway where they:

-Infect a suitable host cell
-They replicate their DNA and protein coats.
-These are then assembled into new virus particles.
-Once the host cell is full of virus particles, it bursts in a process called lysis.
-Other nearby cells can then be infected with the virus.

Question 12

Describe the lysogenic pathway

Answer 12

Viruses can ‘survive’ outside of a shot but they require host cells to reproduce. One way this can be done is by:

The lysogenic pathway occurs when a virus infects a cell but does not immediately replicate so the cell does not burst.
The DNA of the virus is incorporated into the host cell’s DNA, by replicating as the cell divides, causing no harm to the host under normal conditions.
Replication and cell lysis will occur at a later time.

Question 13

Describe Chlamydia.

Answer 13

Chlamydia is a bacteria. It may be symptomless but if not it can cause a burning pain when urinating and often forms a thick yellow or green
discharge from an infected person’s penis or vagina. In women it can also cause bleeding between periods and men can develop swollen testicles.
If untreated, infection with Chlamydia can result in
infertility. Like other bacterial infections, Chlamydia is treated by antibiotics.

Question 13

Explain how sexually transmitted infections (STIs) are spread and how this spread can be reduced or prevented.

Answer 13

STIs are infections which can be spread through sexual contact: including oral, vaginal and anal sex. They are carried in bodily fluids such as semen and vaginal fluid.

The spread of STIs can be reduced using barrier methods of contraception (e.g. condoms) or abstaining from sexual activity.

Question 14

Describe HIV

Answer 14

HIV is a virus. This infection is transmitted by body fluids, often during unprotected sex, but also through cuts and injecting drugs using unsterilized needles. Immediately after infection, people often suffer mild flu-like symptoms. There is no cure for HIV /AIDS although many scientists are trying to find one. Currently, infected people are given antiviral drugs, which can significantly slow the development of AIDS.

Question 14

Describe how some plants defend themselves against attack from pests and pathogens by physical barriers

Answer 14

Examples of plants’ physical barriers:
- A thick cellulose cell wall, which is impermeable to many pathogens
-A thick waxy cuticle on the surface of the leaf, which acts as a barrier to most pathogens

Question 15

Describe how plants defend themselves against attack from pests and pathogens by producing chemicals

Answer 15

-Cells of some plants can produce antimicrobial chemicals, proteins and enzymes.
-Some plants can release compounds that attract larger insects than the pests, which feed on the pests and stop them eating the plant.
-Often, we can extract antimicrobial compounds from these plants for use in drugs such as antibiotics.

Question 15

Describe the method of identifying plant diseases that is observation.

Answer 15

Visible symptoms may include changes in growth, change in colour or blotching of leaves, or lesions (areas of damage on stem or leaves. Symptoms can be checked against photos or other information to suggest a cause.

Question 16

Describe the method of identifying plant diseases that is distribution analysis.

Answer 16

This looks at where the damaged plants occur. Flooding, drought or lack of a soil nutrient will create similar symptoms in all the plants in the area. Diseases that spread by wind will affect plants over a wide area, though most obviously where the wind first reaches the crop. Soil pathogens are usually only found in small areas, and so create an obvious pattern of damaged plants.

Question 17

Describe the method of identifying plant diseases that is sending samples to a lab for testing.

Answer 17

The tests should allow a diagnosis to be made for the problem. Tests can include trying to grow a pathogen from damaged crop plants or using technology to identify the presence of genetic material from a pathogen. Soil samples can also be sent in to be tested for nutrients and toxins. A report will be sent in about observations made.

Question 18

Describe how the physical barriers of skin protects the human body from pathogens.

Answer 18

-Skin is an effective physical barrier as it is very thick over most of the body pathogens can usually only cross this barrier through wounds or by an animal vector that pierces the skin.

Question 19

Describe how the physical barriers of cilia protects the human body from pathogens.

Answer 19

Ciliated cells are specialised to move substances like mucus across their surfaces. This helps to carry dust and pathogens away, either out of the body or into the throat where they enter the digestive system.

Question 20

Describe how the physical barriers of mucus protects the human body from pathogens.

Answer 20

Produced by goblet cells in the airway, mucus traps bacteria and other pathogens before they reach the lungs and cause infection

Question 20

Describe how the chemical defence of lysozymes protects the human body from pathogens

Answer 20

Lysozome is secreted in tears, saliva, mucus and vaginal fluid. It helps to protect the thinner surfaces of the body. Lysozyme is an enzyme that breaks down the cells wall of some types of bacteria, it kills the pathogens or makes them inactive.

Question 21

Describe how the chemical defence of hydrochloric acid protects the human body from pathogens

Answer 21

Some of the cells lining the stomach secret hydrochloric acid, reducing the pH of the stomach contents to about 2. At that acidity, many pathogens are destroyed.

Question 22

How does the immune system attack a pathogen (through lymphocytes)?

Answer 22

-Pathogens have antigens on the surface that are unique to them.
-A lymphocyte with antibodies on its surface that match the antigens on a pathogen will attach to the pathogen.
-This activates the lymphocyte.
-This lymphocyte divides over and over again to produce identical clones.
-Some of the lymphocytes secrete large amounts of antibodies.
-The antibodies stick to the antigens and destroy the pathogen.
-Other lymphocytes remain in the blood as memory lymphocytes, ready to respond immediately if exposed to the same antigen.

Question 23

Describe phagocytes.

Answer 23

White blood cells which are attracted to pathogens. They surround them in the blood, bind to them and engulf them. They do this to all pathogens so are non-specific.

Question 24

Explain the body’s response to immunisation using an inactive form of a pathogen

Answer 24

The pathogen contains a specific antigen. White blood cells release complementary antibodies to the specific antigen. They attach and clump pathogens together. White blood cells engulf the pathogens. Phagocytosis occurs.

Upon a secondary infection the antibodies can be produced much quicker, so the pathogen can be destroyed and the symptoms are not felt.

Question 25

What are the advantages of immunisation?

Answer 25

-They have eradicated many diseases (e.g. smallpox) and reduced the occurence of many.
-Epidemics can be prevented through her immunity where a large proportion of the population is immunised so the spread of the pathogen is reduced as there are less people to catch the disease from.

Question 26

What are the disadvantages of immunisation?

Answer 26

-They are not always effective in providing immunity
-Bad reactions can occur in response to vaccines (although very rare)

Question 27

Explain why antibiotics can only be used to treat antibacterial infections.

Answer 27

Because they inhibit cell processes in the bacterium but not the host organism.

Other pathogens use cell machinery in host cells to reproduce.

Question 28

Explain the use of an autoclave to prepare sterile growth medium and petri dishes

Answer 28

Otherwise, they may be contaminated with other microorganisms. These could be harmless but will compete with the desired bacteria for nutrients and space, or be harmful, potentially producing a new pathogen.

Question 29

Explain the use of sterile inoculating loops to transfer microorganisms

Answer 29

This kills unwanted microorganisms.

These could be harmless but will compete with the desired bacteria for nutrients and space, or be harmful, potentially producing a new pathogen.

Question 30

Explain the need to keep petri dishes and culture vials covered.

Answer 30

Sealing stops airborne microorganisms from contaminating the culture, but it should not be sealed all th3e way around as this would result in harmful anaerobic bacteria growing (due to no oxygen entering).

Question 31

Describe the aseptic technique (and why it’s used) for the core practical investigating the effects of antibiotics

Answer 31

-Glass Petri dishes and
agar gel must be sterilised in an autoclave before use or pre-sterilised plastic Petri dishes can be bought.
Reason – this will kill any bacteria that are present in the solution or on the Petri dishes.
-Pour the sterile agar plates and allow to fully set.
Reason – this provides the selected bacterium with all the nutrients needed to grow.
-Unwrap a sterile spreader or sterilise a spreader in ethanol. Use the spreader to spread the
microorganism
solution, across the entire surface of the agar plate.
Reason – this allows a lawn of bacteria to be produced across the whole of the plate. Replace the lid as soon as possible, secure with tape.
-Label and invert the plate, and store upside down.
Reason – this stops additional unwanted bacteria in the air contaminating the plate. Do not fully seal the lid, as this will stop oxygen reaching the bacterium, and this may encourage harmful anaerobic bacteria to grow. Labels are important, as this identifies the growing bacterium.
-Incubate at a maximum temperature of 25°C in schools and colleges.
Reason – this reduces the chance of growing harmful pathogens.

Question 32

Describe the core practical for investigating the effects of antibiotics.

Answer 32

S-oak filter paper disks in a variety of solutions, use either different concentrations of the same solution, or a variety of different solutions.
Reason - the effectiveness of the solutions at killing the bacteria can be tested.
-Measure the clear area around the soaked filter paper disks. A control disk must be also included. Use a ruler and the equation π r²
Reason - size of zone indicates the effect of the substance tested on the growth of the specific bacterium.

Question 33

Describe the process of developing new medicines.

Answer 33

-Discovery: in plants or microorganisms or synthesised by chemists.
-Development
-Preclinical testing using cells, tissues and live animals
-Clinical testing first on healthy volunteers with a low dose. Then split patients with one group receiving a drug and the other group a placebo so the effect of the drug can be observed.
This then needs to be peer reviewed to check for repeatability.

(Testing needs to check toxicity, efficacy, and dose)

Question 34

Describe the production of monoclonal antibodies

Answer 34

-Scientists obtain mice lymphocytes (a type of white blood cell that make antibodies but cannot divide), which have been stimulated to produce a specific antibody.
-They are combined with tumour cells (do not make antibodies but divide rapidly) to form a cell called a hybridoma.
-The hybridoma can divide to produce clones of itself, which all produce the same antibody
-The antibodies are collected and purified.

Question 35

Explain the use of monoclonal antibodies in pregnancy tests

Answer 35

Monoclonal antibodies are attached to the end of a pregnancy test stick onto which a woman urinates. If she is pregnant, HCG will be present in her urine and will bind to the monoclonal antibodies on the test stick.
The antibodies are attached to blue beads. The antibodies are also present in the result window where antibodies carrying hCG can bind and stay.
Some antibodies with no hCG will move past this to the control window.

Question 36

Explain the use of monoclonal antibodies in locating the position of blood clots/cancer cells

Answer 36

-The monoclonal antibodies are modified so that they will bind to the molecule you are looking for (such as antigens on a blood clot/cancerous cells).
-The antibodies are also bound to a fluorescent dye
-If the molecules are in the sample then the antibodies can bind to it, and the dye can be observed

Question 37

Explain the use of monoclonal antibodies in the treatment of disease, e.g. cancer

Answer 37

*Cancer cells have antigens on their cell membrane called tumour markers which can be targeted.
Three ways to treat cancer with monoclonal antibodies:
-Producing monoclonal antibodies that bind to the tumour markers in order to stimulate the immune system to attack the cells.
-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.
-Using monoclonal antibodies to transport toxic drugs, chemicals or radioactive substances as they can only bind to cancer cells.

Question 38

Explain the advantages of using monoclonal antibodies to target specific cells compared to drug and
radiotherapy treatments

Answer 38

-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 39

Describe how cardiovascular diseases are caused by the interaction of a number of factors

Answer 39

They can be caused by high dietary intake of saturated fat, combined with a sedentary (inactive) lifestyle.
Smoking also increases the likelihood of cardiovascular diseases

Question 40

Describe how
many forms of cancer are caused by the interaction of a number of factors

Answer 40

Smoking greatly increases the risk of lung cancer, whereas the risk of developing breast cancer is largely due to a combination of age and genetics.

Question 41

Describe how some lung and liver diseases are caused by the interaction of a number of factors

Answer 41

Lung and liver diseases are made more likely by smoking and high alcohol intake respectively. However, other factors can play a part - especially age and genetics.

Question 42

Describe how diseases influenced by nutrition are caused by the interaction of a number of factors

Answer 42

Vitamin and nutritional deficiencies are common in anorexic patients, as well as those who can’t absorb or use nutrients properly (including those with celiac disease and anaemia). Obesity, is caused by excess caloric intake and can again be heavy influenced by genetics as some people are more likely to gain weight than others.

Question 43

What is the BMI equation? How is someone classified as obese?

Answer 43

BMI = mass (kg) / (height (m))^2

If someone’s BMI is over 30, they are classified as obese.

Question 44

How can waist-hip ratio b e used to identify obesity?

Answer 44

The waist-hip ratio is calculated by dividing waist circumference (cm) by hip circumference (cm). Obesity is classified as a waist-hip ratio of more than 0.85 for women or 1 in men.

Question 45

Explain the effect of exercise and diet on obesity

Answer 45

-Eating more calories than you burn from physical activity (and everyday metabolism) causes us to put on weight.
-Eating a very large excess of calories, especially if a high proportion of these come from saturated fat, can lead to obesity and related illnesses.
-Obesity is an especially important problem in developed countries such as the UK
-Obesity can lead to developing cardiovascular disease and high blood pressure as fat (lipid) deposits form inside blood vessels.
-It can also contribute to developing Type 2 diabetes, as the body cannot use insulin as effectively when there is a high proportion of body fat

-Sugar tax aims to reduce obesity. Eating fewer processed foods, less sugar, saturated fat and high calorie foods can help reduce the risk of becoming obese.

Question 46

Evaluate life-long medication as a treatment for cardiovascular disease

Answer 46

-There are several medications that will either reduce cholesterol or reduce blood pressure.
-People with very high blood pressure may have to take multiple medications to reduce it.
-They will likely have to take these for the rest of their life

Question 47

Evaluate surgical procedures as a treatment for cardiovascular disease

Answer 47

-Sometimes medication does not work effectively, and surgery may be required.
-Coronary arteries supply the heart muscle with oxygen, and cover the heart.
-If these are blocked, a coronary artery bypass can be performed, where the blocked sections of the coronary artery are ‘bypassed’.
-Another method involves using a metal stent to widen arteries that have been narrowed by fat deposits (atherosclerosis)

Question 48

Evaluate lifestyle changes as a treatment for cardiovascular disease

Answer 48

-Reducing the amount of saturated fat we eat can reduce the risk of developing atherosclerosis (fat deposits in the arteries) and high cholesterol.
-Maintaining a healthy BMI can reduce strain on the heart.
-Taking regular exercise ensures that we remain a healthy weight.
-Reducing amount of salt in the diet, and hanging stress levels, can prevent high blood pressure from developing.