Health is the state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
What is a disease?
A condition where part of an organism doesn’t work properly
What are communicable diseases usually caused by?
Bacteria, viruses, fungi and parasites
What are two types of causes of non-communicable diseases?
Genetics and lifestyle factors
If a person has AIDS, why do they have an increased chance of suffering from diseases like flu?
A person with AIDS is less able to fight off the pathogen that causes flu because their immune system is weakened by the HIV virus
Explain why bacteria such as Salmonella make you feel ill
They produce toxins (poisons) inside the body that damage cells and tissues
What communicable disease is caused by Helicobacter pylori bacteria?
How do viruses replicate?
They live inside body cells and replicate using the cell’s machinery to produce many copies of themselves
How do viruses spread within the body?
Infected cells eventually burst and release the new viruses into the tissue and/or blood
What makes you feel ill when you have a viral infection?
The cell damage caused by infected cells bursting
What are protists?
Eukaryotic organisms that are usually unicellular
What are parasites?
Organisms that live on or inside other organisms and can cause them damage
How do fungi, made up of hyphae (thread-like structures), cause disease in animals and plants?
The hyphae grow and penetrate the skin or surface of plants causing disease. The hyphae can produce spores which can be transferred to other plants and animals
Give an example of a plant disease caused by fungi
Chalara Ash die-back disease
Give examples of human diseases caused by fungi
- Athlete’s foot
State five methods that pathogens are spread
- Drinking or bathing in dirty water
- Airborne (carried in air)
- Swallowing contaminated water or food
- Bodily fluids e.g blood, vomit, saliva
- Animal vectors transmit pathogens
What could infected individuals do to reduce the spread of a pathogenic bacteria?
- Isolate themselves
- Avoid crowded public spaces
- Sleep alone
- Practise good hygiene - cover mouth and nose with tissue when coughing and sneezing, disposing of tissues in a bin
- Good ventilation can reduce likelihood of transmission
What are the main symptoms of an infection caused by Vibrio cholerae?
Diarrhoea that lasts for a few days leading to severe dehydration and ultimately, if untreated, death
How is the pathogen Vibrio cholerae spread?
Through contaminated water sources
Explain why most cases of cholera occur in developing countries
Clean water is not widely available
How can the spread of cholera be reduced?
By making sure that everyone has access to clean water supplies
How does the Heliobacter pylori bacteria cause stomach ulcers?
It inflames the stomach lining which can lead to the lining becoming damaged. The damage allows stomach acid to penetrate the stomach lining, creating a hole (the ulcer) that exposes the tissue underneath
What are the symptoms of stomach ulcers?
Stomach pains, nausea and vomiting
How can the transmission of Helicobacter pylori be reduced?
- clean water supplies
- hygienic living conditions: disinfecting food preparation areas, washing hands before eating or handling food, keep toothbrushes separately
- infected people should not prepare or serve food
- thorough cleaning of utensils
What is Ebola and what does it cause?
A virus that causes haemorrhagic fever
Describe the symptoms caused by Ebola
Fever that causes internal bleeding and bleeding from eyes, nose or mouth, often leading to death
How is Ebola spread?
Through contact with bodily fluids of an infected individual
How was the spread of West African Ebola reduced during the 2013-2016 epidemic? (6 marks)
- infected individuals were isolated from others
- bodies were left untouched until they could be collected by officials wearing protective clothing covering the whole body
- medical staff wore protective clothing coving the whole body
- sterilising areas where the virus may be present
- treatment centres were set up where infected individuals were isolated
- bodies buried in mass graves by people wearing full body protective clothing
- community awareness campaigns about the protective factors individuals could take, eg avoiding contact with infected people and hand washing using soap and water
Describe the symptoms of Chalara ash dieback
Loss of leaves and bark lesions (wounds) leading ultimately to death of tree - directly or because the tree is weakened so much that it cannot defend itself from other pathogens
How is the fungus that causes Chalara ash dieback transmitted?
- through the air by wind - spores
- by the movement of infected ash trees from one area to another
How can the spread of Chalara ash dieback be slowed down?
- removing young infected ash trees and replanting with another species of tree
- putting restrictions on the import and movement of ash trees
How do the vectors become infected?
The mosquitos suck up the malarial protists when they feed on infected animals
How do the vectors infect other animals?
The malarial protist does not affect mosquitos. When mosquitos feed on an animal they introduce the protist into the animals blood stream
What are the symptoms of malaria?
- repeated episodes of fever
- hot and shivery
- muscle pains
- ultimately it can lead to death
What damage can the malaria protist do to the body?
- damage red blood cells
- damage to the liver
What preventative measures can be taken to protect people from mosquitos?
- removing sources of standing water where mosquitoes breed
- upturning containers that are used to collect rain water
- spraying insect repellent onto skin and clothes
- sleeping under a mosquito net
What are the symptoms of Chlamydia?
There are usually no symptoms caused by Chlamydia
What can be the result of an untreated case of Chlamydia?
Infertility in women and in men
How can the transmission of Chlamydia be reduced?
- by wearing a condom during sexual contact
- avoiding sexual contact if infected
- getting treatment - antibiotics
How can a person find out if they have been infected with Chlamydia?
Screening is available - medics can carry out a test for the presence of Chlamydia
How can HIV be controlled?
Treatment leads to a zero viral load which means individuals cannot pass on the virus
How is HIV spread?
Exchanging infected bodily fluids such as blood, semen and vaginal fluids. Exchange of bodily fluids usually occurs during sexual intercourse/ contact and by sharing needles when taking drugs
How can couples reduce the spread of HIV?
- wearing a condom
- getting themselves tested, and if positive, getting and maintaining treatment (medication) to ensure their viral load reaches and stays zero
Describe the structure of viruses
A protein coat around a strand of genetic material
Name the type of pathways that a virus can reproduce through
The lytic pathway and the lysogenic pathway
Which pathway is when the virus is incorporated into the genome (DNA) of the host cell?
Which pathway is when the viral genetic material gets replicated along with the host DNA every time the host cell divides?
Which pathway is when the virus uses protein and enzymes in the host cell to replicate its genetic material and create the components of new viruses?
Which pathway produces host cells that split open once full of new viruses?
Which pathway requires a trigger such as the presence of a specific chemical causes the genetic material to leave the genome and enter the other pathway?
Which pathway leads to the release of new viruses?
During which pathway are new viruses assembled?
During which pathway does the virus lay dormant?
Describe two examples of physical plant defences
- plant leaves and stems have waxy cuticles which are a barrier to prevent entry by pathogens or damage by pests
- waxy cuticles repel water reducing the risk of pathogens transmitted in water
- plant cell walls are made of cellulose which act a barrier to pathogens
- hairy plant leaves and stems prevent pests from reaching the leaf surface to eat them
Describe what chemical defences plants can employ
- produce antiseptics which kill bacteria and fungi
- produce poisons which deter pests
How would a plant pathologist determine if a symptom of disease is due to a nutrient deficiency?
Observe the leaves and determine which nutrient the plant may be deficient in. Add that nutrient to the soil and observe any changes in plant symptoms
How would a plant pathologist determine if a symptom of disease is due to a pathogen?
Analyse the distribution of diseased plants. Use monoclonal antibodies to detect antigens unique to a specific pathogen. Take a tissue sample, then analyse the DNA to detect any pathogen DNA
Give two examples of the body’s physical barriers against pathogens
- skin - barrier which can create a scab to seal any cuts to keep pathogens out
- hair and mucus in nose - physically trap particles
- trachea and bronchi cells - secrete mucus to trap pathogens
- ciliated cells in trachea and bronchi - waft the mucus and any trapped particles and pathogens up to the throat to be swallowed
Give two examples of the body’s chemical barriers against pathogens
- stomach produces hydrochloric acid that kills pathogens
- produce enzymes called lysozymes which kill bacteria - found in tears and mucus
What is phagocytosis?
When a white blood cell engulfs foreign cells and digests them - consuming pathogens
What happens when a B-lymphocyte finds an antigen on a pathogen?
They start to produce antibodies specific to that pathogen
How are antibodies involved in an immune response?
The antibodies bind to the pathogen so
other white blood cells can detect them
and destroy the pathogens
Explain why the immune system response is slow when a pathogen first enters the body
There are only a few B-lymphocytes to
make the new antibody specific to that pathogen. It takes time for the body to produce enough antibody to overcome the infection
Compare and explain the body’s secondary immune response to the primary immune response (when an antigen comes in contact to the immune system for the first time)
It is faster and stronger than the primary
immune response. This is because the memory cells immediately produce antibodies so the body can get rid of the pathogen before any symptoms show
What are vaccines made from?
Small amounts of dead or inactive pathogen
What is immunisation?
Injecting a vaccine into the body to elicit (obtain) an immune response
How does the body react to a vaccine?
White blood cells (B-lymphocytes) produce antibodies to target the dead or inactive pathogens because they still have antigens on their surfaces. Memory lymphocytes are produced.
What happens in a vaccinated body when infected by a pathogen of the same type?
Memory lymphocytes rapidly mass- produce antibodies to destroy the pathogens quickly, preventing symptoms from occurring
What is a vaccination?
When someone is given a vaccine
Why will a person vaccinated against measles still catch chickenpox?
The body will only produce antibodies against measles antigens when vaccinated. It offers no immunity against chickenpox. Vaccines are specific to one pathogen’s antigens
Give two pros of immunisation
- immunisation controls lots of very dangerous diseases (Polio has been completely wiped out)
- epidemics can be prevented by immunisation
Explain -herd immunity-
When a high percentage of a population are immunised, it prevents a pathogen from spreading through the community because there are fewer people to pass it
on. This offers protection to those who cannot be immunised
Which groups of people cannot be immunised?
Too young, too ill and people who have problems with their immune systems eg taking anti-rejection drugs after an organ transplant
If only 50% of a population are vaccinated, what would happen if the pathogen entered the population?
The pathogen could spread very quickly and many people may become ill at the same time. It could develop into an epidemic
Give two cons of immunisation
- vaccines don’t always work
- some people have a bad reaction to a vaccine, but this is rare
What are monoclonal antibodies?
Antibodies produced from lots of clones of a single B-lymphocyte
What is a hybridoma?
Cell produced by fusing a B-lymphocyte with a tumour cell (myeloma) that can be cloned to produce monoclonal antibodies
How are the antigen-specific B-lymphocytes produced?
A mouse is injected with the chosen antigen and given time to develop B-lymphocytes which are then taken from the mouse
How are monoclonal antibodies used in pregnancy tests?
Monoclonal antibodies for the pregnancy hormone HCG are used on the test strips: the part of the strip that is urinated on contains antibodies attached to blue beads. The test strip contains more antibodies to the hormone
Explain what happens on the pregnancy test if a woman is pregnant
If present in the urine the HTC will
bind to the antibodies attached to the blue beads. As the urine moves up the strip the beads and hormone move with it. The beads and hormone then bind to the antibodies on the strip, turning it blue
Explain what happens on the pregnancy test if a woman is not pregnant
HTC is not present. The urine moves up the stick, carrying the blue beads. As there are no antigens attached to the blue beads there is nothing to bind to the antibodies in the test strip, so it doesn’t turn blue.
How does the control window of a pregnancy test work?
The control window strip contains antibodies to the antibodies that bind to the antibodies attached to the blue beads
What are antigens on cancer cells called?
How are monoclonal antibodies used to diagnose cancer?
Monoclonal antibodies specific for the tumour markers are labelled with a radioactive element. Use a drip to give the patient the labelled antibodies into their blood. As they travel around the body, they will bind to any tumour markers they come into contact with. Use a radioactivity sensitive camera to detect bright areas that show where the cancer is, its size and if it is spreading.
How are monoclonal antibodies used to treat cancer?
Monoclonal antibodies are attached to anti-cancer drugs, given through a drip into the blood. The antibodies target the specific cancer cells as they bind to the tumour markers and then release the drug to kill the cancer cell.
What is the advantage of using antibody-based drug therapy?
The side effects are lower because only cancer cells are affected by the drugs
How are monoclonal antibodies used to detect blood clots?
Monoclonal antibodies and proteins in the blood join together to form a mesh. Radioactive element is attached to the monoclonal antibodies and injected into the body. The areas of the clot will be a very bright spot when using a camera that is sensitive to radiation
Why is there a bright spot produced on an image where cancer cells are present?
The radioactive element attached to the monoclonal antibodies attracted to the cancer cells
Name the three main stages in drug testing
- Preclinical tests on cells and tissues
- Preclinical testing on live animals
- Clinical testing on human volunteers
Why is testing a blood pressure drug on cells and tissues unnecessary?
The drug needs a whole circulatory system to be tested on, so needs to be tested on live animals
Why are live animals used in preclinical testing?
- to test efficacy (if it works or not)
- find out toxicity (how harmful)
- best dosage (concentration and frequency)
What is an optimum dose?
The dose of the drug that is the most effective and causes the least side effects
What is a placebo?
A substance that looks likes the drug being tested but doesn’t do anything
Why are placebos used?
So doctors can see the actual difference the drugs makes - it acts as a control
What is the placebo effect?
When patients expect treatments to work and therefore feel better even though the treatment isn’t doing anything
What is a blind trial?
The patient doesn’t know whether they are getting the drug or the placebo
What is a double-blind trial?
Neither the patient nor the doctor knows what is being used until all the results are complete
Some antibiotics inhibit cell wall production. How does this eventually kill the bacteria?
It prevents the bacteria from dividing
How does an antibiotic that targets the synthesis of proteins inside a bacteria work?
Proteins are needed for life process. Without proteins, life processes are impossible so the bacteria will die
Why don’t antibiotics destroy viruses?
Viruses are not cells and do not have a cell wall or make proteins, so antibiotics do not work
What does the growth medium used to culture bacteria contain?
Nutrients such as carbohydrates, minerals, proteins, and vitamins
How is the inoculating loop sterilised?
Placed inside a Bunsen burner flame until it glows red
When investigating the effect of substances on bacterial growth, how are the antibiotics or antiseptics applied to the cultured bacteria?
Paper discs are soaked in the antibiotic/ antiseptic and then placed on a cultured agar plate with spaces between them
What is measured when investigating the effect of substances on bacterial growth?
The radius of the clear area around each disc
What is the area that is measured when investigating the effect of substances on bacterial growth called?
The inhibition zone
What control would be used when investigating the effect of substances on bacterial growth?
A paper disc soaked in sterile water
Why is a control needed when investigating the effect of substances on bacterial growth?
To ensure that the inhibition zones are only due to the antibiotic/ai septic
Give five examples of aseptic techniques
- Sterilised Petri dishes and growth medium using an autoclave/ using steam at high temperature and pressure
- Inoculating loop should be passed through a hot flame
- Liquid bacterial cultures grown in containers with lids
- Once inoculated, the lid of the Petri dish should be lightly taped on
- Petri dish should be stored upside down to stop drops of condensation falling onto the agar surface
How would you calculate the area of a bacterial colony?
Measure the diameter of the colony
From what type of organisms are antibiotics obtained?
Antibiotics are obtained from fungi, or organisms related closely to fungi. Most of them live in the soil
Name some diseases that are associated with smoking
- lung cancer
- stomach ulcers
- bladder cancer
- arterial disease
What is a stroke?
A blood clot in the brain that cuts off blood supply and therefore oxygen supply to brain cells, causing them to die
What does nicotine do to the body?
Increases heart rate and therefore blood pressure
What happens when artery walls are damaged?
Causes a build-up of fatty deposits which restrict blood flow as they get bigger
What do cancer-forming chemicals do to cells?
Causes mutations in the genes that control cell division
Name two diseases for which drinking too much alcohol is a major risk factor
Liver disease such as cirrhosis (scarring of the liver) and liver cancer
How are liver cells damaged?
When enzymes breakdown alcohol, the product damages liver cells. When toxic chemicals leak from the gut due to damaged intestines
What long-term effects can result from an excessive alcohol intake?
Excessive intake of alcohol over a long period can damage the:
- liver (cirrhosis of the liver)
- nervous system
- it may also induce dependence (alcoholism)
How does a lack of vitamin C (causes scurvy), affect the body?
The body cannot produce collagen properly
Give two symptoms of Vitamin C deficiency (scurvy)
- painful joints and muscles
- bleeding gums
How does a low level of exercise increase the risk of disease?
More likely to become obese (very overweight), inactivity linked to high blood pressure and cardiovascular diseases
What are the local effects of high levels of obesity, excessive alcohol consumption and smoking in a community?
Higher occurrence of non-communicable diseases, more pressure for medical services like hospitals
What is the equation for BMI?
BMI = mass(kg) / (height(m))^2
Describe the weight of someone with a BMI of 22
Describe the weight of someone with a BMI of 25
Describe the weight of someone with a BMI of over 40
Describe the weight of someone with a BMI of 35
What is the equation for calculating waist-to-hip ratio?
Waist-to-hip ratio = waist circumference / hip circumference
Above what waist-to-hip ratio are men considered to be carrying too much weight around the middle?
Ratio above 1.0
Above what waist-to-hip ratio are women considered to be carrying too much weight around the middle?
Ratio above 0.8
What is excess weight around the middle called?
Which diseases does a person with excess weight around the middle have higher risk of developing?
- cardiovascular disease
- type 2 diabetes
Which blood vessels are affected by cardiovascular disease?
What causes the narrowing of blood vessels?
Fatty deposits build up on damaged artery surfaces
What is coronary heart disease?
Arteries that supply blood to the heart become narrowed, restricting blood flow which deprives the heart muscle cells of oxygen
What can happen if a coronary artery becomes completely blocked?
Heart muscle cells do not get any oxygen so the start to die, causing a heart attack
Name lifestyle changes that can reduce the risk of cardiovascular diseases
- eat a diet rich in fruit and vegetables
- avoid foods high in saturated fat
- exercise regularly
- lose weight
- avoid an excess of sugary food and drink
- low salt diet
Name the drugs that can reduce the amount of ’bad’ cholesterol in the bloodstream?
What can having too much ’bad’ cholesterol in the bloodstream cause?
Fatty deposits to form on the inside surface of arteries
What do antihypertensive drugs do?
Reduce blood pressure
What do diuretics do to the body?
Help flush out excess water in the body
What do ACE inhibitor drugs do to the body?
Relaxes blood vessels
What do beta-blockers do to the body?
Cause the heart to beat slower and less forcefully
Why do people need to take drugs that reduce the chances of blood clotting?
To reduce the risk of blood clots that could lead to heart attacks or strokes
What are the risks of taking drugs that reduce the chances of blood clotting?
People taking them are more likely to suffer from heavy bleeding if they are injured. Increased risk of internal bleeding
Name a surgical method of treating damage caused by cardiovascular disease
Stents, heart bypass operation
Describe what a stent is
A wire mesh tube that is inserted inside an artery to widen it and keep it open. They widen the artery when inflated by a balloon inserted with the stent. Once in place the balloon is inflated and then deflated before being carefully removed
Where are stents used?
In coronary arteries
What are the advantages of stents?
- effective for a long time
- operation is relatively quick, as is recovery time
What are the risks of stents?
- complications from surgery
- risk of infection from the surgery
- scar tissue may form around the stent, narrowing the artery
- increased risk of blood clots forming near the stent
- procedure may need to be carried out again
What is coronary bypass surgery?
A piece of healthy blood vessel from another part of the body is used to bypass a blocked section of coronary artery
What are the risks of coronary bypass surgery?
- more risks of complications due to longer and more complex surgery
- longer recovery time in hospital and longer time for subsequent recovery
What is a benefit of coronary bypass surgery?
- lower risk of blood clots
- lower risk of having to repeat the surgery
When heart disease is very severe and stents or bypass surgery are not an option, what surgical procedure may need to be carried out when possible?
What is a disadvantage to a heart transplant?
- new heart doesn’t always work properly immediately and may need further treatment until it improves
- the new heart could be rejected by the body due to an immune reaction
Explain the use of immunosuppressant drugs
To prevent rejection of a transplanted organ. They need to be taken for the rest of the person’s life. They suppress the immune system so it does not attack the ’foreign’ heart cells
What is an analgesic?
A pain killing drug