What is World Health Organisation’s (WHO) definition for health?
“A state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.”
What is infirmity?
Weakness or frailness, commonly due to old age.
What is disease?
Disease is condition where part of an organism doesn’t function properly.
What are the two types of disease?
Communicable diseases and Non-communicable diseases.
What are communicable diseases?
Communicable diseases are diseases that can be spread between individuals.
What are non-communicable diseases?
Non-communicable diseases can’t be transmitted between individuals.
If you are affected by one disease what may happen?
If you are affected by one disease, it could make you more susceptible to others - your immune system may become weakened by the disease, so it is less able to fight off other disease.
What are pathogens?
Pathogens are organisms such as viruses, bacteria, fungi and protists that causes communicable diseases.
What are the communicable diseases you need to know?
Cholera Tuberculosis Stomach Ulcers Chlamydia HIV Ebola Malaria Chalara Ash Dieback
What pathogen causes Cholera?
A bacterium called Vibrio cholerae.
What pathogen causes Tuberculosis?
A bacterium called Mycobacterium tuberculosis.
What pathogen causes Stomach ulcers?
A bacterium called Helicobacter pylori.
What pathogen causes Chlamydia?
A bacterium called Chlamydia trachomatis
What pathogen causes HIV?
What pathogen causes Ebola?
The Ebola virus
What pathogen causes Malaria?
What pathogen causes Chalara ash dieback?
What are the symptoms of Cholera?
What are the symptoms of Tuberculosis?
Coughing and lung damage.
What are the symptoms of Malaria?
Damage to red blood cells and, in severe cases, to the liver.
What are the symptoms of Stomach ulcers?
Stomach pain, nausea and vomiting.
What are the symptoms of Ebola?
Haemorrhagic fever (a fever with bleeding).
What are the symptoms of Chalara ash dieback?
Leaf loss and bark lesions (wounds).
What are the symptoms of Chlamydia?
Although it doesn’t always cause symptoms, it can result in infertility in men and women.
How is Cholera spread?
Via contaminated water sources
How is Tuberculosis spread?
Through the air when infected individuals cough
How is malaria spread?
Mosquitoes act as animal vectors (carriers) - they pass on the protist to humans but don’t get the disease themselves.
How are Stomach ulcers spread?
By oral transmission, e.g. By swallowing contaminated water or food
How is Ebola spread?
Via bodily fluids
How is Chalara ash dieback spread?
It is carried through the air by the wind. It also spreads when diseased ash trees are moved between areas.
How can Cholera be reduced?
By making sure that people have access to clean water supplies.
How can Tuberculosis be reduced?
Infected people should avoid crowded public spaces, practise good hygiene and sleep alone. Their homes should also be well-ventilated.
How can malaria be reduced?
By the use of mosquito nets and insect repellent to prevent mosquitoes carrying the pathogen from biting people.
How can stomach ulcers be reduced?
By having clean water supplies and hygienic living conditions
How can Ebola be reduced?
By isolating infected individuals and sterilising any areas where the virus may be present
How can Chalara ash dieback be reduced?
By removing young, infected ash trees and replanting with different species. Also by restricting the import or movement of ash trees.
What does being susceptible to a disease mean?
There are increased chances of getting it
What are viruses?
Usually a protein coat around a strand of genetic material
Are viruses cells?
How do viruses reproduce?
By infecting living cells (host cells), specific types of viruses will only infect specific cells
How do viruses reproduce by the lytic pathway/cycle?
1) the virus attaches itself to a specific host cell and injects its genetic material into the cell
2) the virus uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of the new viruses
3) the viral components assemble
4) the host cell splits open, releasing the new viruses which infect more cells
How do viruses reproduce in the lysogenic pathway/cycle?
1) the infected genetic material is incorporated into the genome (DNA) of the host cell
2) the viral genetic material is replicated along with the host DNA every time the host cell divides, however the virus is dormant and no new viruses are made.
3) eventually a trigger causes the viral genetic material to leave the genome and enter the lytic pathway/cycle
What does it mean if a virus is dormant?
The virus is inactive
What is a trigger that could cause the life cycle of a virus to shift from the lysogenic cycle to the lytic cycle?
The presence of a chemical
What are the lytic and lysogenic pathways /cycles?
Parts of the life cycle of a virus
What are STIs?
Sexually Transmitted Infections, STIs are infections that spread through sexual contact including sexual intercourse
What are the two STIs you need to know about?
Chlamydia and HIV
Some STIs are not only spread by sexual intercourse but what else? Give an example of an STIs which is spread in this way.
Genital contact, Chlamydia
How does the bacterium which causes Chlamydia behave in a similar way to a virus?
It can only reproduce in host cells
How can the spread of Chlamydia be reduced?
By wearing a condom when having sex, screening individuals so hey can be treated for the infection, or by avoiding sexual contact.
What is HIV?
the Human Immunodeficiency Virus
What is the impact of HIV?
It kills white blood cells which are very important for the immune response
What does the HIV infection eventually lead to?
What is AIDS?
Acquired Immune Deficiency Syndrome
What is the impact of AIDS?
The infected person’s immune system deteriorates and eventually fails, because of this the person becomes very vulnerable to opportunistic infections by other pathogens
How is HIV spread?
Via infected bodily fluids
What are some examples of bodily fluids which could be infected by HIV and therefore could spread HIV?
Blood, semen, vaginal fluids
How can the spread of HIV be reduced?
Use a condom when having sex, drug users should avoid sharing needles, medication, screening and proper treatment
How can medication reduce the spread of HIV?
Medication can reduce the risk of an infected individual passing the virus on to others during sex or a mother passing the virus on to her baby during pregnancy, however this means that screening is important to identify the infected individuals for treatment
What physical defences/barriers do plants have against pathogens and pests?
- most plants leaves and stems have a waxy cuticle
* plant cells are surrounded by cell walls
How does a waxy cuticle act as a physical barrier for plants against pathogens and pests?
- The waxy cuticle provides a barrier to stop pathogens entering the plant and to prevent pests damaging the plant.
- a waxy cuticle may also stop water from collecting on the leaf, this could reduce the risk of infection by pathogens that are transferred between plants in water
How does a cell wall surrounding plant cells act as a physical barrier for plants against pathogens and pests?
The cell walls form a physical barrier against pathogens that make it past the waxy cuticle
What are some chemical defences that plants have?
- produce chemicals called antiseptics
* produce chemicals to deter pests from feeding on their leaves
What is the function of antiseptics in plants?
Acts as a chemical defence against pathogens, kills bacteria and fungal pathogens
What are two chemicals from plants which can be used as drugs to treat human diseases or relieve symptoms?
Where is quinine found in plants?
The bark of the cinchona tree
How is quinine used to treat human disease?
For years quinine was the main treatment for malaria
How is aspirin used to relieve symptoms of human disease?
To relieve pain and fever
How is aspirin developed from plants?
It is developed from a chemical found in the bark and leaves of willow trees
In the field how are plant diseases usually detected?
By observations, plant pathologists recognise the symptoms
What are plant pathologists?
Experts in plant disease
What is an example of a symptom in plants which might indicate a specific disease? What types of plants might this disease infect?
Galls may indicate crown gall disease, infects many different types of plants including apple and fruit trees
What is an example of a symptom of a disease that could indicate that the disease is due to environmental causes?
What is an example of an environmental cause?
How is it possible to determine whether a plant is diseased or if the symptoms were due to something else?
By changing the environmental conditions (e.g. adding nutrients to the soil) and observing any change in the plant’s symptoms
What is an example of changing environmental conditions?
Adding nutrients to the soil
How can plant pathologists identify the type of pathogen involved in causing a disease?
By analysing the distribution of the diseased plants
What are two examples of how analysing the distribution of diseased plants can help to identify the type of pathogen causing the disease?
- patches of diseased plants may suggest that the disease is spread through the soil
- a random distribution of diseased plants may suggest an airborne pathogen
What would diseased patches of plants suggest about the causes of a disease?
The disease is spread through the soil
What type of pathogen would be suggested with a random distribution of diseased plants?
An airborne pathogen
What allows accurate identification of specific pathogens?
Laboratory-based diagnostic testing
What two things could laboratory-based diagnostic testing involve?
- detecting antigens
* detecting DNA
How can laboratory-based diagnostic testing by detecting antigens allow accurate identification of specific pathogens?
- antigens in each pathogen are unique
- antigens from a particular pathogen will be present in a plant infected with that pathogen, the antigens can be detected in a sample of plant tissue by using monoclonal antibodies
- the detection of an antigen unique to a particular pathogen allows that pathogen to be identified and the disease diagnosed
How can laboratory-based diagnostic testing by detecting DNA allow accurate identification of specific pathogens?
- if a plant is infected with a pathogen, the pathogen’s DNA will be present in the plant’s tissues
- scientists have techniques to allow them to detect even small amounts of pathogen DNA in a sample of plant tissue, allowing them to identify the particular pathogen that is present
What do physical and chemical barriers do?
Stop pathogens entering the body
What are physical barriers in humans?
Skin, hairs, mucus, cilia
What are chemical barriers in humans?
Hydrochloric acid in the stomach, lysozyme in tears
How does skin act as a physical barrier in humans?
Acts as a barrier and if damaged blood clots quickly to seal cuts and keep microorganisms out
How do hairs and mucus act as physical barriers in the human body?
Hairs and mucus in the nose trap particles that contain pathogens
How does hydrochloric acid act as a chemical barrier in the human body?
The stomach produces hydrochloric acid which kills most pathogens which are swallowed
How does lysozyme act as a chemical barrier in the human body?
The eyes produce the chemical lysozyme in tears, lysozyme kills bacteria on the surface of the eye
Are the physical and chemical barriers we need to know specific or non-specific?
Non-specific because they work against many different types of pathogens
What happens if pathogens enter the body?
The immune system destroys them
What is the most important part of the immune system?
White blood cells
What are B-lymphocytes?
A type of white blood cell that is involved in the specific immune response
What type of molecule are antigens?
What type of molecule are antibodies?
What do memory lymphocytes do?
Give immunity to later infection
When a pathogen enters the body for the first time what is the general speed of the response and why?
Slow because there aren’t many B-lymphocytes to make the antibody needed to lock on to the antigen of the pathogen and memory lymphocytes haven’t been produced to remember the antigens
When a pathogen enters the body for the first time what is the general speed of the response and why?
Fast because there are more cells to recognise the pathogen and produce antibodies against it
Are symptoms of disease shown in the first immune response, the second immune response, or both?
Often only the first immune response because the secondary response is often so quick that the pathogen is removed before symptoms are shown
What does immunisation do?
Stop you from getting infections
What is an example of a disease you can be immunised against?
What does immunisation usually involve?
Injecting dead or inactive pathogens into the body which are antigenic so the body makes antibodies to destroy them even though they’re harmless, the antigens also trigger memory lymphocytes to be made
What does antigenic mean?
what are some advantages of immunisation?
- epidemics can be prevented if a large percentage of the population are immunised (herd immunity can happen with this too)
- some diseases such as smallpox have been virtually wiped out by immunisation programmes.
what are some disadvantages of immunisation?
- immunisation doesn’t always work - sometimes it doesn’t give immunity
- sometimes a person can have a bad reaction to a vaccine but this is very rare
- if a significant number of people aren’t immunised against an epidemic then the disease can spread quickly through them and many people will be ill at the same time.
what is herd immunity?
when not everyone is vaccinated/immunised but even those who are not immunised are unlikely to catch the disease because there are fewer people to transmit the disease
what may having a bad reaction to an immunisation vaccine include?
swelling, or more severe symptoms may be fever or seizures
what are antibodies produced by?
B-lymphocytes (a type of white blood cell)
what are monoclonal antibodies produced from?
many clones of a single B-lymphocyte (all the antibodies are identical and will only target one specific protein antigen)
why is making monoclonal antibodies not as simple as growing more of the B-lymphocytes which can make the antibodies?
lymphocytes don’t divide very easily
what is a myeloma cell?
a type of tumour cell
how is a hybridoma formed?
fusing a myeloma cell with a mouse B-lymphocyte
what is a hybridoma?
a myeloma cell and a B-lymphocyte fused together
how are monoclonal antibodies made?
1) a mouse is injected with a chosen antigen
2) B-lymphocytes are taken from the mouse
3) a sample of fast-dividing tumour cells is taken from the lab
4) a lymphocyte from the mouse is fused with a myeloma (tumour) cell to form a hybridoma cell
5) the hybridoma divides quickly to produce many clones which produce monoclonal antibodies
what usually happens after monoclonal antibodies are produced?
they are collected and purified
why are monoclonal antibodies useful?
monoclonal antibodies can bind to anything (e.g. an antigen that is only found on the surface of one type of cell.) Monoclonal antibodies only bind to the target molecule and so they can be used to target a specific cell or chemical in the body
what hormone is found in the urine of women only when they are pregnant?
what do pregnancy test sticks detect in order to determine if a female is pregnant or not?
the hormone HCG
how do pregnancy test sticks work?
1) antibodies for HCG are on part of the pregnancy test stick to be urinated on. the antibodies have blue beads attatched to them
2) the test strip (what changes colour to show positive or negative for pregnancy) has more antibodies for HCG attatched to it - these antibodies cannot move.
3) the stick is urinated on
4) if pregnant: HCG binds to the antibodies on the stick, the urine moves up the stick which also carries the antibodies (and blue beads) up the stick, the beads and HCG bind to the antibodies on the test strip, the blue beads become stuck to the test strip, this turns the test strip blue. the test is positive.
5) if not pregnant: HCG is not present so nothing binds to the antibodies (with the blue beads), the urine travels up the stick which also carries the blue beads up the stick, the blue beads can’t stick onto the test strip so the stick doesn’t turn blue. The test is negative.
how can the same principles applies in a pregnancy test help with other areas of science?
by using different antibodies in a similar way with the pregnancy test, the test can be used to find other substances in a sample of urine (e.g. antigens on pathogens)
what are tumour markers?
proteins on the cell membranes of cancer cells which are not found on normal body cells
how can monoclonal antibodies be used to diagnose cancer?
1) antibodies are labelled with a radioactive substance
2) the labelled antibodies are given to a patient via a drip so the antibodies go into the patient’s bloodstream and are carried around the body
3) the antibodies bind to the tumour markers when the antibodies come into contact with the cancer cells
4) a photo is taken the patient’s body using a camera which detects radioactivity, the radioactivity from the antibodies bound to the cancer cells will show up on the camera
5) doctors can then see exactly where the cancer is, the size of the tumour, and whether the cancer is spreading
how can monoclonal antibodies be used to treat cancer?
1) an anti-cancer drug is attatched to monoclonal antibodies
2) the antibodies enter a patient’s bloodstream via a drip
3) the antibodies target the specific cells (the cancer cells) by only binding to the tumour markers
4) the drug kills the cancer cells without killing the normal body cells near the tumour
why is using monoclonal antibodies to treat cancer advantageous?
- other cancer treatments (such as using other drugs and radiotherapy) can affect normal body cells as well as killing cancer cells
- therefore the side effects of an antibody-based drug are lower than for other drugs or radiotherapy
what does radiotherapy involve to treat cancer?
firing high-energy beams (like x-rays) straight at a tumour
what happens when blood clots?
proteins in the blood join together to form a solid mesh
how can monoclonal antibodies be used to find blood clots?
1) attatch a radioactive element to monoclonal antibodies which have been developed to bind to the proteins in blood clots.
2) inject the antibodies into the body
3) take a photo using a camera which can detect radioactivity, the photo will show a bright spot where the radiation is and therefore where the blood clot is
list the uses of monoclonal antibodies.
- pregnancy tests
- diagnosing cancer
- treating cancer
- finding blood clots
why are monoclonal antibodies useful for finding blood clots?
a potentially harmful blood clot can be found and disposed of before the patient is harmed
what are antibiotics used for?
treating bacterial infections
how do antibiotics work?
by inhibiting processes in bacterial cells but not in the host organism
what is an example of how antibiotics can affect bacteria?
some antibiotics inhibit the building of bacterial cell walls, this prevents the bacteria from dividing and eventually destroys the bacteria whilst having no effect on the cells in the human host (don’t have cell walls)
why is it important to be treated with the correct antibiotic?
different antibiotics destroy different types of bacteria
what can’t antibiotics destroy? why?
viruses because viruses reproduce using the body’s cells. this makes it difficult to develop drugs that destroy the virus without killing the body’s cells
what is penicillin?
who discovered penicillin?
today, how do most scientists discover new drugs?
by using their knowledge of how a disease works, in order to try and identify molecules that could be used as drugs to fight the disease.
what does the development of a new drug involve?
preclinical and clinical testing
what does preclinical testing involve?
first testing drugs on human cells and tissues in the lab, but for drugs which affect multiple or whole body systems, the drug must be tested on a whole animal.
the drug must then be tested on live animals.
in preclinical testing, why must a drug be tested on live animals?
to test that the drug works (produces desired effect), to find out how toxic (harmful) the drug is, and to find the best dosage.
what does clinical testing involve?
testing a drug on human volunteers
what are the two stages of clinical testing?
first testing on healthy human volunteers, then testing on humans suffering from the illness the drug is for
why are drugs first tested on healthy human volunteers during clinical testing?
to ensure that the drugs don’t have any harmful side effects when the body is working normally
why are the drugs tested on people suffering from the illness in clinical testing?
the drugs are tested on people suffering from the illness to find the optimum dose of the drug which is most effective and has the fewest side effects.
what is a placebo?
a substance that looks like the drug being tested but doesn’t do anything
what is the placebo effect?
when the patient expects the treatment to work and so feels better even though the treatment isn’t doing anything
How is the second stage of clinical testing kept fair?
- Testing patients split randomly into two groups - one with a placebo and one with the actual drug.
- clinical trials are double blind -both the patient AND the doctor don’t know whether they are getting the drug or the placebo.
Why is the second stage of clinical trials often blind?
To allow for the placebo effect and so that the doctors monitoring the patients and analysing the results aren’t subconsciously influenced by their knowledge.
What is the final stage of the development of a new drug?
To be approved by a medical agency before it is used to treat patients
How are bacteria grown in the lab?
They are cultured (grown) in a growth medium
What does a growth medium contain?
Carbohydrates, minerals, proteins and vitamins needed for growth
What can a growth medium fir growing bacteria be?
A nutrient broth solution or solid agar jelly
What will bacteria grown on agar plates form?
Visible colonies on the surface of the jelly or will spread out to give an even covering
How do you make an agar plate?
- hot agar jelly is poured into shallow round plastic dishes (Petri dishes)
- when the jelly has cooled and set, microorganisms can be transferred to the agar jelly to multiply.
What are two methods of transferring microorganisms to agar jelly?
- inoculating loops can be used
* or a sterile dropping pipette and spreader can be used to get an even covering of bacteria.
What temperature are cultures of microorganisms kept at in the lab at school? Why? How is this different to the temperature scientists may use?
Around 25 degrees because harmful pathogens are less likely to grow at this temperature
Scientists may use a higher temperature to provide optimum growth conditions
What is the difference between antibiotics and antiseptics?
Antibiotics kill bacteria inside the body, antiseptics kill bacteria outside the body
How can you perform a practical to investigate the effect of antibiotics on bacteria growth?
1) place paper discs soaked in different types of antibiotics on an agar plate that has an even covering of bacteria. Leaving some space between the discs.
2) the antibiotic should diffuse into the agar jelly. Antibiotic-resistant bacteria will continue to grow on the agar around the paper where the bacteria have died - this is the INHIBITION ZONE.
3) ensure that there is a control - a paper disc that has not been soaked in an antibiotic.
4) leave the plate for 48 hours at 25 degrees
Why may you have a control for the practical investigating the effect of antibiotics on bacterial growth?
This is so you can compare the difference between the growth of the bacteria around the control disc and the growth of bacteria around one of the antibiotic disc. This shows that the growth of bacteria is due to the antibiotic alone.
Give examples of how aseptic technique can be applied in the practical for antibiotics
- Petri dishes and growth medium must be sterilised before use (autoclave)
- inoculating loop should be sterilised by passing it through a hot flame to kill unwanted microorganisms
- liquid bacterial cultures kept in a culture vial with a lid - lid only removed briefly when transferring bacteria to prevent other microbes getting in
- Petri dish should be covered with a lid lightly taped on to stop microorganisms from air getting in
- Petri dish should be stored upside down
Why should the Petri dish be stored upside down?
To prevent drops of condensation falling on the agar
What does an autoclave do?
Uses steam at high pressure and temperature to kill and unwanted microorganisms
How do you calculate inhibition zones?
Area = πr²
What is there to note when calculating inhibition zones?
Don’t open the Petri dish to measure inhibition zones - should be visible through bottom of dish
How can you find the area of a colony?
Use πr² but measure the diameter (to use as radius) of the colony first
How is smoking a major risk factor associated with CVD?
- nicotine in smoke increases heart rate so increases blood pressure
- high blood pressure damages artery walls so contributes to build up of fatty deposits in arteries. The deposits restrict blood flow and increase risk of heart attack or stroke
- smoking increases risk of blood clots forming in arteries which can restrict blood flow, leading to heart attack or stroke
What is drinking alcohol a major risk factor for?
The development of liver disease e.g. cirrhosis because alcohol is broken down by enzymes in the liver and some of the products are toxins. Drinking too much over a long period of time can cause permanent liver damage.
What is the number one cause of death worldwide?
What is the equation for BMI?
Weight (kg) / (height m)²
What is the BMI value for underweight?
What is the BMI value for normal?
18.5 - 24.9
What is the BMI value for overweight?
25 - 29.9
What is the BMI value for moderately obese?
What is the BMI value for severely obese?
Why isn’t BMI a reliable measure of obesity?
Athletes have lots of muscle which weighs more than fat so they could have a high BMI even though they’re not overweight
How do you calculate waist to hip ratio?
Waist circumference (cm) / hip circumference (cm)
What is the circumference of a person’s waist or hips?
The distance around the entire way around their body at that point
What is the value for waist to hip ratio which indicates abdominal obesity in men?
What is the value for waist to hip ratio which indicates abdominal obesity in women?
What is cholesterol?
A fatty substance required by the body to make things like cell membranes
Where do fatty deposits in arteries occur?
In areas where the artery wall has been damaged
What can fatty deposits trigger to form in arteries? What is the impact of this?
Blood clots, this can block blood flow completely and can cause heart attack or stroke
What drugs can decrease the risk of heart attack or stroke?
Statins, anticoagulants, antihypertensives
What do statins do?
Decrease the amount of cholesterol in the bloodstream, this slows the rate at which fatty deposits form.
What negative side effects can statin have?
Aching muscles and/or liver damage
What do anticoagulants do?
Make blood clots less likely to form
What is an example of an anticoagulant?
What is a negative side effect or anticoagulants?
Can cause excessive bleeding if the person is hurt in an accident
What do antihypertensive do?
Decrease blood pressure which helps to prevent damage to blood vessels and so reduces the risk of fatty deposits forming
What negative side effects can antihypertensives have?
Headaches and fainting
What are stents?
Tubes inserted into arteries to keep arteries open to ensure blood passes through the heart muscles and lowering the risk of a heart attack.
What are the surgical options to prevent heart attack?
Stents, coronary bypass surgery, donor heart replacement
What is coronary bypass surgery?
If part of a blood vessel is blocked, a piece of healthy vessel taken from elsewhere can be used to bypass the blocked section.
How do stents negatively affect arteries? How can this be prevented?
Irritate the artery and make scar tissue grow, take drugs to stop blood clotting on stent
What are disadvantages of heart replacement with a donor?
The new heart doesn’t always start pumping properly and drugs have to be taken to stop the body rejecting it. The drugs may have side effects: more vulnerable to infections