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What is health?
A state of complete physical, mental, and social wellbeing and not merely the absence of disease or infirmity
What is a communicable disease?
A disease that is passed directly between individuals, caused by a pathogen
What is a non-communicable disease?
A disease that cannot be transmitted between individuals, generally long lasting with a slow onset, caused by lifestyle, environmental conditions, genetic mutations etc
Why can having one illness increase the likelihood of catching another?
Disease can weaken a person’s immune system, making them more susceptible to catching other diseases
What is a pathogen?
A disease causing organism such as a virus, bacteria, protist or fungi
Cholera
Caused by bacteria, symptoms of vomiting and diarrhoea, spread through water
How can the spread of cholera be reduced?
Increased access to clean water and improved sanitation
Tuberculosis
Caused by bacteria, symptoms of chesty cough, wheezing (caused by lung damage), and is spread through air
How can the spread of tuberculosis be reduced?
Improved hygiene, social distancing, self-isolating in a ventilated space
Chalara ash dieback
Caused by a fungus, symptoms of dark lesions on bark and blackened leaves which wilt and die, spread though spores in the air
How can the spread of chalara ash dieback be reduced?
Controlling the movement of ash trees, killing infected plants, and replanting with a different species
Malaria
Caused by protists, symptoms of fever or chills and anaemia caused by damage to blood and the liver, spread through animal vectors (mosquitos)
How can the spread of malaria be reduced?
Using mosquito nets, insect repellant and covering your arms and legs
Stomach ulcers
Caused by heliobacter pylori bacteria, symptoms of stomach pain, vomiting, nausea, spread by consuming infected food and drink
How can the spread of stomach ulcers be reduced?
Having access to clean water, improved hygiene and improved sanitation
Ebola
Caused by a virus, symptoms of diarrhoea, vomiting and internal bleeding, and is spread through bodily fluids
How can the spread of Ebola be reduced?
Improved hygiene, isolating, sterilising outbreak areas
Describe the lytic pathway
The virus binds to specific receptors on the host cell and injects DNA into the host cell. It replicates its DNA using the host cell machinery to make new viral structures until the host cell ruptures (bursts), releasing new viruses into the body
Describe the lysogenic pathway
The virus binds onto the specific receptors on a host cell and injects its viral DNA into the host cell, so that the virus’ and the host cell’s DNA become integrated. The DNA replicates every time the host cell divides but the cell’s functions remain normal. A trigger causes an activation of the DNA so it enters the lytic pathway
HIV
Caused by a virus, causes destruction of white blood cells, leading to an increased susceptibility to other diseases such as AIDS, spread by infected bodily fluids
How can the spread of HIV be reduced?
Use of condoms and protected sex, blood screen testing, disallowing breastfeeding from infected mothers, not sharing needles
How can the spread of chlamydia be reduced?
Screening, use of condoms and protected sex
Physical defences in plants and their functions
Waxy cuticle: prevents entry of pathogens
Cell wall: further barrier against pathogens
Chemical defences in plants and their functions
Secretion of toxins: reduce damage by pests
Production of antibacterial chemicals: kills bacteria
How can plant diseases be detected and identified (in the field)?
Observation of symptoms, analysis of the distribution of the infected plants to determine pathogen and transmission mode, changing environmental conditions to eliminate other causes (such as nutrient defiencency)
How can plant disease be identified (in the lab)?
Detection of antigens using monoclonal antibodies, DNA analysis to check for pathogen DNA
The body’s physical defences and their functions
Cilia: waft mucus with trapped pathogens to the back of the throat to be swallowed
Skin: protective surface barrier
Blood clotting: prevents pathogen entry through blood
The body’s chemical defences and their functions
Tears: contains lysozymes which kill bacteria by digesting cell walls
Hydrochloric acid in the stomach: acidic pH kills pathogens
How does the immune system defend the body against disease?
The body is exposed to a pathogen, which has a unique antigen which are detected by receptors on the white blood cells. This triggers an immune response which starts the production of antibodies by b-lymphocytes. Each antibody is specific to an antigen and binds to it to clump pathogens together to be engulfed by phagocytes. Some lymphocytes become memory lymphocytes, so that, if the body is re-infected, antibodies can be reproduced faster and the pathogen can be destroyed before causing symptoms
What is a vaccine and how do our immune systems respond to them?
Deliberate exposure of an individual to a dead or inactive version of antigens triggers the production of antibodies and provides immunity to that pathogen due to memory lymphocytes remaining in the body for a long time after first exposure. The individual wont contract the disease again as they have been immunised
What are the advantages of vaccines?
Herd immunity: allows protection to those who cannot receive immunity from vaccines
Vaccines also prevent epidemics or pandemics
What are the disadvantages of vaccines?
There is a higher mutation rate of viruses, they are not guaranteed to work, inactive pathogens may mutate, vaccines are expensive
Why can’t antibiotics treat any other pathogens?
Antibiotics only inhibits the growth of bacteria as it destroys their cell walls, and has no effect on host cells so cannot treat viruses
What are the stages of testing for new medicines?
Discovery, development, preclinical trials, clinical testing
What happens during preclinical trials?
Drugs are tested on cultured human cells to determine toxicity and efficiency. The drugs are then tested on live animals to establish a safe dose for humans and observe side effects
What happens during clinical testing?
The drug is tested on healthy human volunteers. The drug is then tested on patients with the disease to determine efficiency, and the dosage is slowly increased until the optimum dosage is found
How are monoclonal antibodies produced?
An antigen is injected into a small rodent, which triggers the production of antibodies and then memory lymphocytes. The antibodies are harvested and then combined with myeloma cells to form a hybridoma, which reproduces rapidly and the antibodies are collected
How are monoclonal antibodies used in pregnancy testing kits?
Monoclonal antibodies are injected into a two places on a pregnancy test - attached to blue beads but free to move, and fixed to the test stick. These antibodies test for the hormone hCG in the woman’s urine. The hormone binds to the monoclonal antibodies attached to the blue beads then diffuse up the stick until monoclonal antibodies fixed to the stick bind to the hormone too and a blue line forms to show a positive pregnancy test result
What are the advantages to using monoclonal antibodies to target specific cells rather than drugs or radiotherapy?
Healthy cells are damaged as a result when drugs or radiotherapy is used, while monoclonal antibodies only target cancer calls, reducing the overall damage
How are monoclonal antibodies used to diagnose cancer?
They are tagged to a radioactive substance, then injected into the patient’s blood where it binds to tumour markers on cells and the emitted radiation is detected using a special scanner enabling doctors to determine the location of cancer cells
How are monoclonal antibodies used to treat cancer?
Monoclonal antibodies attach to an anti-cancer drug and are injected into the blood, where the monoclonal antibodies bind to the tumour markers and the anti cancer drug destroys the cancerous cells
How are monoclonal antibodies used to identify blood clots?
They are attached to a radioactive substance and bind to specific proteins in blood clots. The radiation emitted by the monoclonal antibodies is identified, enabling blood clots to be found
How does exercise and diet affect obesity and malnutrition?
Regular exercise decreases fat stores, reducing the chances of obesity, but malnourishment can lead to both obesity and malnutrition
How is BMI calculated?
BMI=mass/height²
How is hip-waist ratio calculated?
Wait circumference/hip circumference
How does alcohol affect the risk of liver diseases?
Alcohol breaks down into toxic products in the liver which can build up and cause scarring to the tissue
How does smoking effect the risk of cardiovascular diseases?
Nicotine raises the heart rate, increasing the risk of cardiovascular diseases. Carbon monoxide lowers the ability of red blood cells to carry oxygen, so the heart rate increases, also increasing the risk of cardiovascular diseases
Evaluate the treatment of cardiovascular diseases
Lifestyle and diet changes: can enhance the efficiency of other methods of treatment despite not being effective themselves
Life-long medication: reduces some of the effects of cardiovascular diseases but can have nasty side effects
Surgical procedures: can be a permanent solution to a disease but comes with risks
