How does the WHO define health?
A state of complete physical, mental, and social well being
What is a communicable disease?
A disease that can be spread between individuals
What is a non-communicable disease?
A disease that cannot be transmitted between individuals
What causes cholera? What are its effects, how does it spread, and how can you reduce transmission?
A bacterium called Vibrio cholerae
Via contaminated water sources
Using clean water supplies
What causes tuberculosis? What are its effects, how does it spread, and how can you reduce transmission?
A bacterium called Mycobacterium tuberculosis
Coughing and lung damage
Through the air by coughing
Infected people should avoid public spaces, have good hygiene, sleep alone, and have well ventilated homes
What causes malaria? What are its effects, how does it spread, and how can you reduce transmission?
Damage to red blood cells, later the liver
Mosquitos are animal vectors
Use of mosquito nets and insect repellent
What causes stomach ulcers? What are its effects, how does it spread, and how can you reduce transmission?
A bacterium called Helicobacter pylori
Stomach pain, nausea and vomiting
Oral transmission e.g. swallowing contaminated water or food
Having clean water supplies and hygienic living conditions
What causes ebola? What are its effects, how does it spread, and how can you reduce transmission?
Via bodily fluids
Isolating infected individuals and sterilising areas where the virus may be present
What causes chalara ash dieback? What are its effects, how does it spread, and how can you reduce transmission?
A fungus that infects ash trees
Leaf loss and bark lesions
Carried through the air by the wind and when diseased trees are moved
Removing young infected ash trees and replanting them with different species and restricting the import or movement of ash trees
What is the lytic pathway?
A way viruses reproduce in cells, by attaching itself to a specific host cell and injecting its genetic material into the cell. The virus then uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of new viruses. The viral components assemble and the host cell splits open, releasing the new viruses, which infect more cells.
What is the lysogenic pathway?
A way viruses reproduce in cells, when the injected genetic material is incorporated into the genome (DNA) of the host cell. The viral genetic material gets replicated along with the host DNA every time the host cell divides, but the virus is dormant and no new viruses are made. Eventually a trigger (e.g. the presence of a chemical) causes the viral genetic material to leave the genome and enter the lytic pathway.
What causes chlamydia? What are its effects, how does it spread, and how can you reduce transmission?
A kind of bacterium that behaves similarly to a virus as it can only reproduce inside host cells. It does not always cause symptoms but can result in infertility. Wear a condom during sex and screen individuals so they can be treated.
What causes HIV/AIDS? What are its effects, how does it spread, and how can you reduce transmission?
A virus (Human Immunodeficiency Virus) that kills white blood cells, eventually leading to AIDS (Acquired Immune Deficiency Syndrome), where a person’s immune system deteriorates and eventually fails, so a person becomes vulnerable to other infections. It is spread by some bodily fluids (e.g. blood, semen, vaginal fluids). Use a condom during sex, avoid sharing needles, and screen often and get treatment.
What are some plant physical defences?
Leaves and stems have a waxy cuticle, which provides a barrier to stop pathogens entering and pests from damaging them, as well as water collecting on them, reducing the risk from water borne pathogens
Plant cells are surrounded by cell walls, which forms another physical barrier
What are some plant chemical defences?
Antiseptics, which kill bacterial and fungal pathogens
Chemicals which deter pests from feeding on their leaves
What are some plant chemicals used to help humans?
Quinine - comes from the bark of the cinchona tree, for years was the main treatment for malaria
Aspirin - found in the bark and leaves of willow trees, used to relieve pain and fever
How can plant diseases be detected?
Observations - plant pathologists recognise symptoms such as galls to determine the disease
Distribution - patches of diseased plants could show it is spread through the soil and a random distribution may suggest an airborne pathogen
How can a plant disease be differentiated from an environmental cause?
Changing the environmental conditions (e.g. adding nutrients to the soil) and observing any change in the plant symptoms
How is detecting antigens used for diagnosing plant diseases?
Pathogens have unique antigens on their surface, so they will be present in a plant infected with the pathogen and detected in a sample of tissue. This allows the pathogen to be identified and the disease diagnosed.
How is detecting DNA used for diagnosing plant diseases?
A pathogen’s DNA will be present in an infected plant’s tissues. Scientists can detect even small amounts of this DNA in a sample, allowing them to identify the particular pathogen that is present.
What are some physical barriers in the body to stop pathogens?
Skin is a barrier and blood clots quickly seal cuts to keep microbes out
Hairs and mucus in the nose trap particles that contain pathogens
Cells in the trachea and bronchi produce mucus to trap pathogens, while other cells have cilia, which waft the mucus to the throat, where it can be swallowed
What are some chemical barriers in the body to stop pathogens?
The stomach produces hydrochloric acid, which kills most swallowed pathogens
The eyes produce lysozyme in tears, which kills bacteria on the surface of the eye
What is the role of B-lymphocytes in the immune response?
When they come across an antigen on a pathogen, they start to produce proteins called antibodies, which bind to the pathogen so that it can be found and destroyed by other white blood cells. These are produced rapidly and flow round the body to find all similar pathogens.
What is the role of memory lymphocytes in the immune response?
The first time a pathogen enters the body the immune response is slow as there are not many B-lymphocytes to produce the right antibody. As well as antibodies, memory lymphocytes are also produced in response to a foreign antigen, which remain in the body for a lomb time and remember the specific antigen. If the pathogen returns, there are more cells to recognise it and produce antibodies, so the secondary immune response is much quicker.
What is immunisation?
Injecting dead or inactive pathogens into the body which are antigenic. The body produces antibodies to help destroy them, so memory lymphocytes are produced. Then, if live pathogens of the same type get into the body, a secondary immune response is triggered, so the person is far less likely to get the disease.
What are the pros and cons of immunisation?
Epidemics can be prevented if a large proportion of people are immunised, as un-immunised people are also less likely to get the disease, as there are fewer people to pass it on (herd immunity)
Some diseases like smallpox have been virtually wiped out by immunisation
It does not always work
Sometimes there are rare bad reactions to a vaccine such as swelling, fever, or seizures
What are monoclonal antibodies?
Antibodies produced from lots of clones of a single B-lymphocyte. They are identical and will only target one specific antigen
What is a hybridoma?
A cell created by fusing a mouse B-lymphocyte with a type of tumour cell called a myeloma cell that divides very quickly. It therefore produces lots of monoclonal antibodies
How are monoclonal antibodies used in pregnancy tests?
A specific hormone (HCG) is found in the urine of pregnant woman. The bit of the stick you wee on has antibodies attached for the hormone with blue beads attached. The test strip has more of these antibodies stuck onto it. If you are pregnant the hormone binds to the antibodies, which moves along in urine, and then binds to the other antibodies, meaning the blue beads get stuck, turning it blue. If you are not pregnant, the urine washes the first antibodies away, so there is no colour change.
How can monoclonal antibodies be used to diagnose cancer?
Cancer cells contain tumour markers - proteins on their cell membranes that are not found on healthy cells. Monoclonal antibodies are produced that bind to these and are labelled with a radioactive element. They are given to the patient through a drip and bind to tumour markers, so a radioactive spot will show up by the cancer in pictures that detect radioactivity.
How can monoclonal antibodies be used to treat cancer?
An anti cancer drug is attached to monoclonal antibodies and given through a drip. The antibody only binds to tumour markers on cancer cells, so the drug only kills cancer cells without affecting nearby healthy cells, reducing side effects
How can monoclonal antibodies be used to find blood clots?
When blood clots, proteins in the blood join together to form a solid mesh. Monoclonal antibodies that bind to these proteins are attached to a radioactive element. They are injected into the body and a picture that picks up radiation is taken, which shows a bright spot for the blood clot.
How are antibiotics used to treat infections?
They inhibit processes in bacterial cells but not in the host organism, such as the building of cell walls. This stops them dividing, eventually killing them, but does not affect human cells. Different antibodies treat different types of bacteria. They do not affect viruses as they reproduce using body cells, so it is hard to affect one but not the other.
What is preclinical testing?
The first stage of drug testing, where drugs are tested on human cells and tissues in the lab, which shows the effects at a small level but not on the whole organism. Live animals are then used to see if it works, to see how harmful it is, and to find the best dosage.
What is clinical testing?
Testing a drug on healthy volunteers to find side effects. Then testing a drug on people with the disease to find the optimum dose. The gold standard is double blind placebo testing, where there are two groups, with one getting a placebo pill to see if the drug has a substantial effect, and neither the patients nor the doctor know which group has the real drug and which the placebo.
How can you grow bacteria in a lab?
Use an agar plate, with agar jelly in a Petri dish. The agar jelly is a growth medium, containing carbohydrates, minerals, proteins, and vitamins needed for bacteria to grow. Use an inoculating loop or sterile pipette and spreader to transfer bacteria in. Keep it at about 25 degrees to stop harmful pathogens growing.
How can you investigate the effects of substances on bacterial growth?
Put paper discs soaked in different types of antibiotics on an agar plate with an even covering of bacteria, leaving space between them. Inhibition zones where bacteria die form around them. Use a control of a clean paper disc - there should be no inhibition zone. Leave the plate for 48 hours at 25 degrees; the better the antibiotic, the larger the inhibition zone.
What is the difference between antiseptics and antibiotics?
Antiseptics kill bacteria outside the body; antibiotics kill bacteria inside the body
What aseptic techniques need to be used in the practical of investigating antibiotics?
Sterilise the Petri dish and growth medium with an autoclave, which uses steam at a high pressure and temperature to kill microorganisms
Pass the inoculating loop through a hot flame before transferring bacteria
Keep liquid bacteria cultures in a culture vial with a lid; only remove it briefly
Cover the Petri dish with a lid afterwards and lightly tape it on
Store the Petri dish upside down to stop condensation drops falling on the agar
How can you calculate the size of inhibition zone?
Use Area = pi x r^2
What are risk factors?
Things linked to an increase in the likelihood that a person will develop a certain disease during their lifetime
Why is smoking a risk factor for cardiovascular disease?
Nicotine increases heart rate, increasing blood pressure
High blood pressure damages artery walls, which contributes to the build up of fatty deposits in the arteries, which restrict blood flow and increase the risk of heart attacks and strokes
Smoking increases the risk of blood clots in arteries, which can restrict or block blood flow, which can cause heart attacks and strokes
What are some common risk factors for malnutrition, obesity, and liver disease?
A diet with too many or too few nutrients
Not getting enough exercise and a diet high in fat and sugar
Drinking goo much alcohol - some products from breaking down alcohol are toxic
How can non-communicable diseases affect communities?
They put pressure on resources of local hospitals, which is costly at the national level as the NHS is funded by the government. People may not be able to work, affecting the economy. In developing countries malnutrition can hold back development, affecting things on a global level.
How is BMI calculated?
BMI = weight (kg) / (height (m))^2
What are some key values for BMI?
<18.5 - underweight
18.5-25 - normal
25-30 - overweight
>30 - obese
How is waist to hip ratio calculated?
Waist to hip ratio = waist circumference / hip circumference
What waist to hip values indicate that you are carrying too much weight around your middle for men and women?
Men - >1
Women - >0.85
What is cardiovascular disease?
Any disease associated with the heart and blood muscles
What is cholesterol?
A fatty substance the body needs to make things like cell membranes. Too much cholesterol in the blood can cause fatty deposits to build up in arteries, restricting blood flow.
Where do fatty deposits occur in arteries?
In areas where the artery wall has been damaged e.g. by high blood pressure
What causes heart attacks and strokes?
When fatty deposits in arteries trigger blood clots to form. These can block blood flow completely, causing a heart attack if the artery supplies the heart muscle, depriving it of oxygen, and a stroke if it is a blockage in the brain.
What lifestyle changes can treat CVD?
Eating a healthy, balanced diet low in saturated fat can lower cholesterol levels.
Losing weight, exercising regularly regularly, and stopping smoking also help.
What drugs reduce the risk of heart attacks and strokes? What are their downsides?
Statins - reduce cholesterol in the bloodstream, but can have side effects like aching muscles and liver damage
Anticoagulants - make blood clots less likely to form, but can cause excessive bleeding in accidents
Antihypertensives - reduce blood pressure, but can have side effects like headaches and fainting
What surgical procedures reduce the risk of heart attacks and strokes? What are their downsides?
Stents - tubes inserted into arteries, keeping them open so blood can pass through. Over time the artery can narrow again as stents can irritate the artery and make scar tissue grow. Drugs need to be taken to stop blood clotting on them
Coronary bypass surgery - If part of a blood vessel is blocked, a piece of healthy vessel can be taken from elsewhere and be used to bypass the blocked section
Donor heart - Replaces the old heart. Does not always start pumping properly, drugs must be taken to avoid rejection, which can have side effects like an increased risk of infections
They are all very expensive and there is risk of bleeding, clots, and infection