B5- Disease and Bioenergetics

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  • Created by: sana.aaa
  • Created on: 24-01-18 18:10

Health and disease:

  • your health is the physical and mental well-being
  • communicable diseases are caused by pathogens, such as bacteria and viruses that can be passed from one person to another
  • no- communicable diseases cannot be transmitted from one person to another, e.g. heart diseases and arthritis)
  • diet- if you do not get enough to eat, or the right nutrients you may suffer from diseases. too much food, or the wrong type of food, can lead to problems such as obesity, some cancers, or type 2 diabetes
  • stress- a certain level of stress is inevitable in everyone's life and is probably needed for our bodies to function properly
  • life situations- including your ethnic group, your gender, how many children you have, your financial status.
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Pathogens and disease:

  • communicable diseases, also known as infectious diseases, are found all over the world
  • microorganisms that cause disease are called PATHOGENS- they may be bacteria, viruses, protists, or fungi, and they infect animals and plants, causing a wide range of diseases
  • communicable disease is caused by directly by a pathogen or by a toxin made by a pathogen
  • the pathogen can be passed from one infected individual to another who doesn't have the disease
  • some are fairly mild- common cold and tonsillitis
  • other are known killers- tetanus, influenza, and HIV/ AIDS
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Bacteria and Viruses:

  • bacteria and viruses cause the majority of communicable diseases in people
  • in plants, viruses and fungi are the most common pathogens
  • bacteria are single-celled living organisms that are much smaller than animal and plant cells
  • bacteria are used to make food such as yogurt and cheese, to treat sewage, and to make medicines
  • viruses are even smaller than bacteria and they cause disease in every type of living organism
  • bacteria divide rapidly by splitting in two (BINARY FISSION). They may produce toxins that affect your body and make you feel ill. Sometimes they directly damage your cells
  • viruses take over the cells of your body, they live and reproduce inside the cells, damaging and destroying them
  • common disease symptoms are a high temp, headaches, and rashes
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Pathogens:

  • by air: (including droplet infection). Many pathogens including bacteria, viruses, and fungal spores are carried and spread from one organism to another in the air. When you are ill, you expel tiny droplets full of pathogens from your breathing system when you cough, sneeze or talk
  • by direct contact: this is common in plant diseases, where a tiny piece of infected plant material left in a field can infect an entirely new crop. In people, diseases including STDs, such as chlamydia, are spread by direct contact of the skin Pathogens such as HIV/AIDS enter the body through direct sexual contact, cuts, scratches and needle punctures that give access to the blood
  • by water: fungal spores carried in splashes of water often spread plant diseases. for humans, eating raw, undercooked, or contaminated food or drinking water containing sewage can spread diseases such as diarrhoeal diseases, cholera, or salmonellosis. the pathogen enters your body through your digestive system
  • when people live in crowded conditions with no sewage system, infectious diseases can spread very easily. LIFESYTLE FACTOR EXAMPLE
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Growing bacteria in the lab:

  • to culture(grow) microorganisms, you must provide them with everything they need- this means giving them a liquid or gel containing nutrients--- A CULTURE MEDIUM. This contains carbohydrate as an energy source, various minerals, a nitrogen source so they can make proteins, and sometimes other chemicals. Most microorganisms need warmth and oxygen to grow
  • hot AGAR GEL is poured into a petri dish, it is then left to cool and set
  • you to need uncontaminated cultures of microorganisms to investigate the effects of chemicals such as disinfectants and antibiotics
  • contamination can come from your skin, the air, the soil, or the water around you. it is important to avoid any unnecessary contamination- the bacteria you want to grow may be harmless, however, there is always the risk that a mutation (a change in the DNA) will take place and produce a new and dangerous pathogen
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Growing useful organisms:

  • the Petri dishes on which you will grow your microorganisms must be sterilised before use, the nutrient agar must also be sterilised to kill off any unwanted microorganisms. glass dishes can be sterilised by heating. a special oven called an AUTOCLAVE is often used- it sterilises using steam at high pressure. 
  • the next step is to inoculate the sterile agar with the microorganisms you want to grow
  • once you have inoculated your plates, the secured Petri dishes need to be incubated for several days so the microorganisms can grow. Petri dishes should be stored upside down so condensation does not fall from the lid onto the agar surface
  • sterilise the inoculating loop used to transfer microorganisms to the agar by heating it until it is red hot in the flam of a Bunsen and then letting it cool. do not blow on it as it cools
  • dip the sterilised loop in a suspension of the bacteria you want to grow and use it to make ZIG ZAG streaks across the surface of the agar. replace the lid on the dish as quickly as possible to avoid contamination
  • fix the lid of the Petri dish with adhesive tape to prevent microorganisms from the air contamination the culture- or microbes escaping. do not seal all the way around the edge- as oxygen needs to get into the dish to prevent harmful anaerobic bacteria from growing
  • label and store upside down to stop condensation falling onto the agar surface
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Growing bacteria in schools:

  • in school labs, the maximum temperature at which cultures are incubated is 25*C
  • if you cultured bacteria at 37*C (human body temperature), there would be a high risk of growing some dangerous pathogens
  • if you use a lower temperature, you reduce the likelihood of growing pathogens that might be harmful to people
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Viral diseases:

  • measles- symptoms include: fever and red skin rash. the virus is spread by inhalation of droplets from coughs and sneezes and is very infectious. measles is a serious disease- can cause blindness and brain damage and may be fatal if complications arise
  • HIV/AIDS: around 35 millions people globally are infected with HIV, a virus that can eventually lead to AIDS. In 2013, around 1.5 million people died of HIV- related illnesses. HIV attacks the immune cells and after the initial mild illness, it remains hidden inside the immune system, sometimes for years. HIV is spread by direct sexual contact, and the exchange of body fluids such as blood, which occurs when drug users share needles or when unscreened blood is used for transfusions. Also can be spread by breast milk
  • TMV- tobacco mosaic virus, was the first virus ever to be isolated, it is a widespread plant pathogen that affects around 150 species of plants including tomatoes and tobacco plants. It causes a distinctive mosaic pattern of discolouration on the leaves as the virus destroys the cells- this affects the growth of the plant because the affected areas of the leaf do not photosynthesise. it is spread by contact between diseased plant material and healthy plants. the virus can remain infectious in the soil for about 50 years
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Bacterial diseases: salmonella:

  • bacterial diseases affect animals and plants
  • antibiotics kill bacteria or stop them from growing and cure bacterial diseases- however, bacteria can become resistant to them
  • SALMONELLA- are bacteria that live in the guts of many different animals- found in raw meat, poultry, eggs. when they enter our bodies, they disrupt the balance of the natural gut bacteria and cause salmonella food poisoning. one common cause is undercooked food, when the bacteria hasn't been killed by heating- or if the food is prepared in unhygienic conditions where the food is contaminated with salmonella bacteria from raw meat. 
  • the symptoms develop within 8-72 of eating infected food- fever, abdominal cramps, vomiting, and diarrhoea are caused by the bacteria and the toxins they secret
  • no antibiotics are given because they don't last long
  • in young children and elderly, it can be fatal, usually because of DEHYDRATION
  • in the UK, poultry is vaccinated against salmonella to control the spread of the disease
  • it can be prevented by washing hands and surfaces after handling raw chicken, and cook chicken thoroughly, and avoid washing raw chicken (water splashes around the kitchen spreading the bacteria)
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Gonorrhoea :

  • it is a sexually transmitted disease (std), which are also known as sexually transmitted infections (STIs)
  • it is spread by unprotected sexual contact with an infected person
  • has symptoms in the early stages but then becomes relatively symptomless
  • early symptoms include thick yellow/ green discharge from the vagina or penis and pain on urination
  • 10% of infected men and 50% of infected woman get no symptoms at all
  • untreated gonorrhea can cause long-term pelvic pain, infertility, and ectopic pregnancies
  • babies born to infected mothers may have severe eye infections and even become blind
  • can be treated with antibiotics
  • because of evolving bacteria, these bacteria have become resistant so it is increasingly difficult to treat
  • can be prevented by contraception
  • and by reducing the number of sexual partners
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Fungal diseases:

  • athletes foot is a well known, minor fungal skin condition
  • a small number of human fungal diseases can be fatal when they attack the lungs or brains of people who are already ill
  • ROSE BLACK SPOT: a disease of rose leaves, it causes purple or black spots to develop on the leaves. the leaves often turn yellow and drop early- this weakens the plant because it reduces the area of leaves available for photosynthesis. as a result, the plant does not flower well
  • the spores are carried by the wind, and it can be spread by water when water drips onto the leaf then splashes onto another one
  • can be prevented by removing and burning affected leaves and stems
  • chemical fungicides can also help to treat the disease, and prevent it spreading
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Protist diseases:

  • protists are a type of single-celled organism- they cause a range of diseases in animals and plants
  • diseases caused by protists usually involves a vector that transfers the protists to the host
  • MALARIA: it is a disease caused by protist pathogens that are PARASITES- they live  and feed on other living organisms
  • the protists reproduce sexually in the mosquito and asexually in the human body, the mosquitos act as vectors of the disease
  • the protists travel around the body in the circulatory system- they affect the liver and damage red blood cells
  • malaria causes recurrent episodes of fever and shaking when the protists burst out of the blood cells, it can be fatal
  • can be prevented by using impregnated insect nets to prevent mosquitoes biting humans, using insecticides to kill mosquitoes in homes
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Human defence responses:

  • the skin covering your body, prevent bacteria and viruses reaching the tissues beneath. if you damage or cut your skin, the barrier is broken but your body restores it. you bleed, and the platelets in your blood set up a chain of events to form a clot that dries into a scab. this forms a seal over the cut, stopping pathogens from getting in
  • the nose if full of hairs and constantly produces a sticky liquid, MUCUS. the hair and the mucuxstraps particles in the air that may contain pathogens or irritate your lungs
  • your trachea and bronchi- also secrete mucus that traps pathogens from the air . the lining of the tubes is covered in CILIA- tiny hair like projections from the cells, which waft the mucus up to the back of the throat where it is swallowed
  • the stomach produces ACID, and this destroyed the microorganisms in the mucus you swallow
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The immune system :

  • the white blood cell ingests microorganisms, they destroy and digest the microorganisms so they cannot make you ill
  • white blood cells produce antibodies, that target a specific bacteria or viruses and destroy them. you need a unique antibody for each type of pathogen. when your white blood cells have produced antibodies once against a particular pathogens, they can be made quickly if that pathogen gets into the body again. this stops you from getting the disease twice
  • white blood cells can also produce antitoxins- they produce antitoxins, which counteract the toxins released by the pathogens
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Plant disease:

  • insect pests may both destroy plants directly and act as vectors of disease
  • one important group of insect-plant pests is the APHIDS
  • aphids have sharp mouthparts that penetrate into the phloem vessels of the plant so they can feed on the sugar-rich phloem sap
  • aphids attack in huge numbers, depriving the plant cells of the products of photosynthesis- this damages and weakens the plant
  • aphids also act as vectors, transferring viruses, bacteria, and fungi from diseased plants into the tissues of healthy plants on their mouthparts
  • aphids can be destroyed using chemical pesticides
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Mineral deficiency- in plants:

  • some plant diseases are the result of mineral deficiencies in the soil where the plant is growing- they are non-communicable, so they are not passed from one plant to another plant
  • need enough nitrate ions from the soil to convert the sugars made in photosynthesis into proteins that are needed for growth in protein synthesis. if there is a nitrate deficiency in the soil, protein growth will be limited,therefore the growth of the plant will be stunted and they will not produce a crop properly
  • plants take magnesium ions from the soil to make the chlorophyll needed for photosynthesis, if the level is low the plant cannot make enough CHLOROPHYLL. the leaves become yellow and growth slows down because the plant cannot photosynthesise properly. the yellowing of the leaves due to lack of magnesium ions is known as CHLOROSIS
  • mineral ions can be replaced using fertilisers fairly quickly, the damage can be repaired if minerals are replaced quick enough
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Detecting disease:

  • stunted growth- nutrient deficiency
  • spots on leaves-black spot fungus on roses
  • discolouration- yellowing is chlorosis
  • discolouration- mosaic pattern is tobacco mosaic virus
  • presence of pests-  aphids or caterpillars
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Plant defense responses:

  • PHYSICAL BARRIERS:
    • cellulose cell walls- strengthen plant cells help to resist invasion by microorganisms. when aphids pierce through the cellulose cell wall, it creates a way for pathogens into the cells
    • tough waxy cuticle- acts as a barrier to the entry of pathogens, it is only at the stomata where pathogens have an access to the cells within the leaf
    • bark on trees- form a protective layer, that is hard for pathogens to penetrate.w hen the dead cells are lost or shed, the pathogens fall off with them
    • leaf fall- deciduous trees lose their leaves in autumn. any pathogens that infect the leaves, such as rose black spot, fall off the tree when the leaves are lost
    • CHEMICAL BARRIERS:
    • many plants produce antibacterial chemicals that protect them against invading pathogens, and these are very effective at preventing bacterial diseases in many plants
    • as current antibiotics become less effective, scientists are increasingly investigating plant antibacterial chemicals to see if they can be adapted for use as antibiotics against human pathogens
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Defnese against herbivores:

  • sometimes plants have to defend themselves against the large and small animals that want to eat them
  • MIMICRY-some plants droop to mimic unhealthy plants, and this tricks animals into not eating them. some plants mimic butterfly eggs on their surfaces, so real butterflies do not lay eggs on them to avoid competition with other caterpillars
  • DROOPING/ CURLING- when they are touched, a rare but effective adaptation is for the leaves to collapse suddenly, dislodging insects and frightening larger animals
  • HAIRY STEMS and/ or LEAVES- deter insects and animals from feeding on them or laying their eggs on the leaves or stems,
  • THORNS- make it unpleasant or painful for large herbivores to eat them
  • POISONS- deter herbivores, because the animals learn to avoid plants that make them feel unwell
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