SB5 Health, Disease and Development of Medicines

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  • Created by: Sia11
  • Created on: 06-11-20 18:43

SB5a Health and disease

  • Good health is a state of complete physical, social and mental well-being, improving one of these can also improve the others
  • A disease is a problem with a structure or a process in the body that is not the result of an injury
  • Microorganisms that cause diseases and change body processes are called pathogens and the diseases caused by these are communicable diseases (they can be passed on)
  • Non communicable diseases do not pass on from person to person, they are caused by a problem in the body
  • Diseases can be correlated; one disease means a person is more likely to have another disease. Possible causes of this include: 
    • One disease damages the immune system, making it easier for other pathogens to cause disease
    • A disease damages the body's natural barriers and defences allowing pathogens to get into the body more easily
    • A disease stops an organ system from working properly, making other diseases more likely to occur
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SB5b Non-communicable diseases

  • There are several different types of non-communicable diseases; some are genetic, while other can result from poor diet or malnutrition
  • Malnutrition is when a person gets too little or too much of particular nutrients from their food; this could cause a deficiency disease.
  • Kwashiorkor is caused by a malnutrition in protein, scurvy is caused by a malnutrition in vitamin C, rickets or osteomalacia is caused by a malnutrition in vitamin D and calcium, and anaemia is caused by a malnutrition in iron
  • Some non-communicable diseases are caused by how we choose to live - our lifestyle
  • Ethanol is found in alcoholic drinks and it is a drug, it changes how the body works
  • Ethanol is broken down by the liver, and a large amount of ethanol taken over a long period can lead to liver disease, including liver cirrhosis, a cirrhotic liver does not function well and can result in death
  • Liver disease is the fifth largest cause of death in the UK, deaths from alcohol related liver disease have increased by 450% in the last 30 years in the UK
  • The cost of treating people with liver disease is more than £500 million each year and is still rising
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SB5c Cardiovascular disease

  • Obesity is where large amounts of fat are formed under the skin and around organs such as the heart and kindneys, it is caused a diet too high in sugars and fats
  • Too much fat can increase the risk of many diseases, including cardiovascular disease which is a result of the circulatory system functioning poorly, a symptom of this is high blood pressure leading to heart pain or even a heart attack
  • Body mass index (BMI) is a way to measure/estimate the amount of fat on the body, it uses height (cm) and mass (kg). The formula is BMI = mass/height squared
  • Another way of measuring this, is by the waist-to-hip ratio, dividing the waist measurement by the hip measurement (this method is better for measuring abdominal fat than BMI)
  • Smoking can lead to cardiovascular disease as tobacco smoke contains many harmful substances that can damage the lungs when breathed in, and can be transported around the body. These can damage blood vessels, increase blood pressure, make vessel narrower and increase the risk of blood clots forming in blood vessel, leading to cardiovasular disease
  • Damage to blood vessels can cause the build up of fat: first substances from tobacco smoke damge the artery lining. Then fat build up in the atery wall at the site of damge, making the artery narrower, Here a blood clot may block the artery here, or break off and block an artery in another part of the body causing a heart attack or a stroke
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SB5d Pathogens

  • Cholera causes severe diarrhoea, Filippo Pacini suggested that the bacterium caused the disease, Robert Koch proved that Vibrio Cholerae was the cause in 1883
  • Tubercolosis is caused by a bacterium called Mycobacterium tubercolosis, this infects and damges the lungs, resulting in blood specked mucus after coughing, fever and weight loss
  • Plants are often infected infected by fungi, chalara dieback is a disease of ash trees, symptoms include lesions on the trunk and braches and leaves dying earlier than usual
  • Malaria is one of the greatest causes of human death from infection and it is caused by a protist, which multiplies inside red blood and liver cells (causes fever, weakness and sickness)
  • Viruses are not true organisms as they do not have a cellular structure. They multiply by infecting a cell and taking over the cell's DNA copying processes to make new viruses
  • The ebola virus causes the breakdown of blood vessels and liver and kidney cells, this leads to internal beeding and fever, causing haemorrahegic fever
  • HIV attacks and destroys white blood cells in the immune system. HIV often leads to AIDS becuase their their immune systems cannot protect them fro secondary infections.
  • Many types of bacterium live in our bodies, some are essential for our health, but others may not affect us. Over 50% of people have Helicobacter pylori batheria in their stomachs but 80% never show symptoms, others may develop ulcers
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SB5e Spreading pathogens

  • Most Pathogens cannot grow outside their host, so must spread from one host to another so they can increase in number, if we know how they spread, we can find ways to stop it
  • Infections (colds, flus, tubercolosis etc.) cause people to sneeze and cough - sends droplets containing pathogens into air, in the air, flu can survive a day but TB bacteria can survive months and mixes with dust that can blow around infecting more people
  • Fungi (causes chalara dieback) can also spread through the air, as tiny spores (cells that grow into new organism), these can be carried long distances thorugh winds.
  • Bacteria that can be spread in water (e.g. cholera, typhoid+dysentery) are rare in developed countries as water is treated to kill pathogens, outbreaks occur where hygiene is difficult
  • Pathogens of the digestive distem cna be spread in food as well as water, they enter through the oral route (mouth). Heliobacter is thought to be spread when people touch other peoples food after touching their mouths or after going to the toilet, or on the feet of flies
  • Some pathogens (e.g. ebola) require extreme hygiene practices to control them as they enter easily through broken skin, or the eyes, nose or mouth
  • Some pathogens cannot survive in the environment so are spread in other ways, e.g malaria protist is carried in blood by mosquitoes that sucked blood from an infected person. Organisms that carry pathogens from one person to another are called vectors.
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SB5f Virus life cycles

  • All viruses contain one or more strands of genetic material surrounding by a protein coat, or caspid, although many have additional layers surrounding the capsid
  • Viruses can't replicate themselves so they enter a living cell and take over the cell's processes making genetic material and proteins, different viruses take over different of cells.
  • Lytic cycle - Virus attaches itself to cell and injects genetic material, viral genetic material forms a circle, new viral genetic material and proteins are produced and assembled, cell lyses (breaks open) releasing the viruses
  • Lysogenic cycle - Virus attaches itself to cell and injects genetic material, viral genetic material forms a circle, viral genetic material inserts itself into the bacterial chromosome, acterium reproduces normally, replicating viral genetic at each cell division, cell and viral genetic material may reproduce many times, occasionally, the virus genetic material separates from the bacterial chromosome, causing a lytic cycle
  • The effect of viruses on the bacteria can be studied using bacterial lawn plates, these plates are made with nutrient agar, on top of which a thin layer of bacteria grows. A solution contain viruses is added to the plate , after a day or two, clears circles can be seen where bacteria have been killed by the viruses.
  • The cross-sectional area of a clear circle is calculated by the equation pi x radius2
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SB5g Plant defences

  • Physical defences:
    • The outer surfaces of leaves and stems are covered by a waxy layer clled a culticle, this makes it difficult for pathogens to get to the cells beneath
    • Woody plants, such as bushes and trees, protect their stems with a thick layer of bark
    • These are not good protection against herbivores whose teeth can pierce through them
  • In addition they use chemical defences:
    • Some produce chemical substances to deter pathogens and herbivores only when they are attacked (e.g. wild potatoes), these are repellents
    • Others (e.g. floxgloves) produce these substances all the time, however, this takes energy, so it must be worth the cost to the plant to make them, these are poisons
  • Many medicines we use use were developed from substances that plants to protect themselves, for example, aspirin was originally producedfrom salicylic acid which is made by severals. Another example is artemisinin which is used to kill the Plasmosdium protists that cause malaria, it was originally extracted from the wormwood plant
  • Most new medicines are produced using chemical substances in a lab, new medicines are tested on cultures of bacteria or human cells. These must not become contaminated so aseptic techniques are used, e.g. an autoclave to sterilise equipment and growth medium
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SB5h Plant diseases

  • Plants show signs of stress whenever conditions are't good for growth, e.g. where there is too much or little water, when the soil lacks nutrients or when they are being attacked
  • The stress may be caused by a combination of factors, identifying the cause is essential so the farmer can treat the crop properly and prevent loss of yield
  • Identifying the cause of stress usally starts with observation for visible symptoms (changes in growth, change in colour of leaves, lesions, etc.)
  • Symptoms for different problems may look similar, and symptoms for the same problem may look different in different plants in the same crop
  • Distribution analysis looks at where the damaged plants occur, flooding, drought or lack of nutrients will create similar symptoms in all the plants in the area (soil pathogens are found in small areas), diseases that spread by wind will afftect plants over a large area
  • Sometimes the only way to get a definite identifying of a crop disease is to send samples to a lab for testing. The tests allow a diagnosis of the problem to found, these tests can include trying to grow a apthogen from damaged crop, or using technology identify the presence of genetic material from a pathogen from a pathogen
  • When farmers send damaged plants for testing, they send reports of other observations they made, they may also send soil samples, this helps the lab to be more certain of the cause
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SB5i Physical and chemical barriers

  • The physical barrier of our bodies is skin which is very thick over most of the body, the only way a pathogen can get cross is through a wound of by a vector that pierces the skin
  • The skin has additional defences as it contains glands that secrete substances onto the skin surfaces, these substances include lysozyme , which is an enzyme that breaks down the cell walls of types of bacteria, it is a chemical defense as it kills pathogens or makes them inactive. Lysozyme is also found in tears, saliva and mucus where it protects thinner surfaces
  • Mucus is a sticky substance produced by cells lining openings that pathogens could use to enter the body, dust and pathogens get stuck in the mucus
  • Cells that line the inside of the nose and tubes in the breathing system have cilia, these are specilised to move substances across their surfaces, this carries dust and pathogens away
  • Everything that comes from the respiratory system pass through the oesophagus into the substance in the stomach and in the stomach there is hydrochloric acid, this reduces the pH of the subtances to about 2, at this acidity many pathogens are destroyed
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SB5i Physical and chemical barriers 2

  • The reproductive system has atural defences such as lysozyme in vaginal fluid and mucus
  • Some pathogens can overcome defences in the reproductive system. These pathogens are usually transmitted throughsexual activity and are called STIs, these include HIV and Chlamydia.
  • Both of these can be spread through contact with sexual fluids, this transmition can be reduced or prevented by avoiding direct contact with these fluids 
  • Both of these pathogens may be passed from a mother to her unborn child
  • HIV may be passed from an infected person to others in blood, e.g. sharing needles
  • Many people with STIs are not aware that they are infected, screening helps to identify an infection so they can be treated for the disease
  • Blood given to people who have lost a lot of blood, is first screened to make sure it does not comntain HIV particles or other pathogens
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SB5j The immune system

  • Sometimes pathogens manage to get through all the physical barriers and chemical defences, it is then up to the immune system to attack the pathogen
  • Alll cells and virus particles have kolecules on their outer surface called antigens, the immune system uses thes antigens to identify if something is wrong to identify if something inside the body is a cell from the body or has come from outside the body
  • White blood cells called lymphocytes have other molecules on their surfaces called antibodies, a lymphocyte with antibodies on its surface that match the the shape of the antigens on a pathogen will attach, this stops the pathogen from working
  • Lymphocyte is activated and divides rapidly to produce identical lymphocytes with the same antibodies. Some of these release large amounts of antibody molecules into the blood, this may kill the pathogen or cause othe part of the immune system to destroy them
  • When all the pathogens have been killed, some of the lymphocytes that match that pathogen's antigens remain in the blood, these are memory lymphocytes so if the same pathogens attack you again your body with produce a much faster secondary response
  • Immunisation can be triggered artificially by using a vaccine which injects weakened or inactive pathogens into the body so that a secondary response will be triggered if you are ever attacked by this pathogen
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SB5k Antibiotics

  • Alexander Fleming noticed that after he left an agar plate of bacteria for several weeks, a mould had grown which had killed, he dicovered the mould made penicillin, the first antibiotic
  • Antibiotics are substances that kill bacteria or inhibit their cell processes, they do not have this effect on human cells making them useful for for attacking bacterial infections the immune system cannot control
  • Many kinds of antibotic have been developed that work in different ways, this is important because different types of bacteria have different structures and they do not respond in the same way
  • A major problem with using antibiotics is that many kinds of bacteria are evolving resistance, as a result new antibiotics and medicines must be devoloped to control the infection
  • Pre-clinical testing: The first step in the development of a possible new medicine when it is tested on cells or tissues in the lab
  • Clinical trial: The second step (only if the fisrt stage is successful) where the medicine may be tested on animals to see how it works in a whole body, if this is successful, it is tested on a small number of healthy people, to check if side effects are minor
  • Large clinical trial: The medicine is used in a large amount of people who have the disease , this helps to work out the dosage and to check for different side effects
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