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B3 - Infection and Response (Communicable Disease (There are several types…
B3 - Infection and Response
Communicable Disease
There are several types of pathogens. Pathogens are microorganisms that enter the body and cause disease
Pathogens can be viruses, bacteria, protists or fungi
Bacteria - Small living cells. Bacteria can reproduce rapidly inside the host's body. They cause us to feel unwell by producing toxins that damage cells and tissues.
Viruses are not cells - They are much smaller than cells. They reproduce rapidly inside the host organism. They live inside the cells of the host and use the cells natural processes to reproduce themselves and burst from the cell releasing new viruses. They damage cells and cause us to feel ill.
Protists - are single-celled Eukaryotes. Some protists are parasites. Parasites live on or in other organisms and can cause damage to them. They are often transferred by a vector, the vector does not get the disease. E.g. Malaria
Fungi - Some fungi are single-celled, other fungi have a body that is made up of hyphae (thread-like structures). These hyphae can grow and penetrate the human skin and the surface of plants, causing damage. The hyphae can produce spores, which spread the disease to other organisms.
Pathogens can be spread in different ways - 3 most common:
Water - Some pathogens can be spread through water contamination with the pathogen, this could be an example of cholera (a bacterial infection).
Air - Pathogens can be carried in the air and can then be breathed in. some airborne pathogens are carried in the air in water droplets produced by coughs or sneezes. E.g. Influenza virus.
Direct contact - Some pathogens can be spread via direct contact with the pathogen, such as skin contact. e.g. athletes foot, a fungal infection that can be spread by the direct contact with the person or the persons clothing times such as socks or shower towels.
Viral and Fungal disease
Measles - is spread by droplets from an infected person's sneeze or a cough. Develop a red skin rash and show signs of a fever. Measles is very serious and can be fatal if complications occur. Measles can lead to pneumonia or a brain infection called
encephalitis
.
HIV - HIV is a virus that is spread via sexual contact or via the exchange of bodily fluids such as blood.In the first few weeks, flu-like symptoms occur. There are usually no symptoms for several years. During this time HIV can be controlled using antiretroviral drugs, these stop the virus replicating. The virus attacks the immune cells. IF the virus damages the immune system severely it cannot cop with other diseases, this is known as late-stage HIV or AIDS.
TMV - TMV is a virus that affects many species of plants. It causes mosaic patterns to develop on the leaves, parts of the leaves become discoloured. This discolouration causes photosynthesis to be interrupted and prevents plant growth as photosynthesis cannot occur to produce energy.
Rose Black Spot - Is a virus that causes purple or black spots to develop on the leaves of the plants. The leaves turn yellow and drop off. This means photosynthesis is interrupted, so the plants cannot grow.The disease can be treated with fungicides and by stripping the infected leaves from the plant to prevent the disease from spreading via spores. The leaves must be destroyed.
Preventing disease
The spread of disease can be reduced or prevented.
Being hygienic - use simple hygiene methods such as hand washing can prevent the spread of pathogens.
Destroying vectors - By reducing the number of vectors this reduces the spread of the pathogen, this can prevent infection with the pathogen. Vectors that are insects can be killed using insecticides or by habitat removal so they can no longer breed.
Isolating individuals - If you isolate an infected individual this prevents the risk of the pathogen spreading.
Vaccination - Vaccinating people and animals against pathogens means that they cannot develop the infection and then pass it on to another organism.
Protist and Bacterial diseases
Malaria is a disease caused by a Protist. Part of the malarial life cycle process occurs inside a mosquito. The mosquitos are vectors for the pathogen, the pick up the protists when feeding on the blood of infected animals. Every time the mosquito feeds on another animal is spreading the protists by inserting it into the other animals blood. People can be protected by mosquito nets and insecticides.
Salmonella - is a type of bacteria that causes food poisoning. Infected people can suffer from a fever, stomach cramps, vomiting and diarrhoea. These symptoms are caused by the release of toxins into the body by the bacteria cells. It can be obtained from contaminated foods being ingested. E.g. eating chicken that has not been prepared correctly and still contains the bacteria when consumed.
Gonorrhoea - is a sexually transmitted disease. It is transferred via sexual contacts, such as having unprotected sex. Gonorrhoea is caused by a bacteria. Symptoms include pain when urinating, and a thick yellow discharge from the vagina or penis. To prevent the spread of gonorrhoea, people can be treated with antibiotics and should use barrier methods of contraception such as condoms or femidoms.
Fighting disease
Vaccination
Vaccination protects from future infections. A vaccination involves injecting a small amount of dead or inactive pathogens. These carry antigens, which cause your body to produce antibodies to attack these antigens. The pathogen is harmless to humans as it is dead or inactive.
Pros: 1. Vaccines have helped control many communicable diseases that were common in the Uk such as polio and tetanus. 2. Large epidemics of diseases can be prevented if a large percentage of the population is vaccinated against the pathogen. If a large quantity of the population is not vaccinated against the pathogen then the risk of an epidemic increases.
Cons: Vaccines don't always work, sometimes they do not give immunity to the pathogen. Bad reactions can be incurred from a vaccine, however, these bad reactions are rare.
Drugs
Antibiotics (e.g. penicillin) kill or prevent the growth of the pathogen without killing any of the bodies cells. Antibiotics do not kill viruses as viruses reproduce using the bodies own cells.
Painkillers can be used to relieve the pain felt from a disease, such as aspirin. They do not actually tackle the cause of the disease or kill pathogens. Other drugs such as cold remedies also do the same.
Bacteria can become resistant to antibiotics. Bacteria can mutate and become resistant to antibiotics. Some strains of an infection can become resistant to the antibiotics so the resistant strands of the infection cannot be treated.
To prevent antibiotic resistance antibiotics must be controlled in order for the use of them not to become common and risk antibiotic-resistant strains of serious diseases such as MRSA. Patients must also finish the entire course of antibiotics.
Many medicines originally came from Plants. Plants produce many chemicals that act as defences against pathogens that could attack them. Some other drugs were extracted from microorganisms, for example penicillin was produced from penicillium mould.
There are 3 main stages in drug testing: Preclinical testing the pathogens on human cells and tissues in a lab environment. After this, the drugs are tested on live animals. This is to test efficacy, to find out about its toxicity and to find the best dosage. After this, the final stage is testing on human volunteers in a clinical trial. The drug is tested on both healthy and unhealthy (to ensure the side effects are not affected by other factors of health within the patients). Some people are given a placebo instead of the actual drug to ensure the side effects are correct.
Immune system
The immune system attacks pathogens that enter the body. The key component of the immune system is the white blood cells that are carried within the blood. They have 3 main attack types:
The pathogens can be consumed and engulfed by the white blood cells to prevent therefrom producing toxins and stop the effects of the pathogen. The process of digesting pathogens is called phagocytosis.
White blood cells can produce antibodies, these antibodies bind to the pathogen and allow the white blood cells to attack the pathogens cells. Every invading pathogen has unique molecules (antigens) on its surface. When white blood cells come across an unknown antigen on a cell they produce the antibodies white produce a specific antigen for the cell and this occurs rapidly. This allows the other white blood cells to be notified and attack the pathogens cells. If the pathogen is reingested the white blood cells will produce the antibodies to kill the pathogen much more quickly. This person is now naturally immune.
Antitoxins can be produced to counteract toxins produced by the invading bacteria.
Bodies defence systems
The skin acts as a physical barrier to pathogens. It also secretes antimicrobial substances which kill pathogens.
Hair and muscus in the nose trap particles that could contain pathogens.
The trachea and bronchi secrete mucus to trap pathogens. The trachea and bronchi are also lined with cilia cells that move the mucus up and out of the lungs where it can be swallowed and the pathogens can be killed in the hydrochloric acid of the stomach.
Monoclonal antibodies
Monoclonal antibodies are identical antibodies. Antibodies are produced by B-lymphocytes (a type of white blood cell). Monoclonal antibodies are produced from lots clones of a single white blood cell. This means all the antibodies are identical and will only target one specific protein antigen. To produce the clones the b-lymphocytes has to be fused with a tumour cell as they must divide rapidly. Monoclonal antibodies can bind toanything
Monoclonal antibodies are used in pregnancy tests. The hormone present in the urine of a women when pregnant (HCG) binds to the antibodies on the blue beads on pregnancy test when pee'd on. The blue beads get stuck to the strip causing it to turn blue and suggest pregnancy. If the hormone is not present the urine travels up the pregnancy test but does not bind the blue beads to it therefore not turning the strip blue.
Monoclonal antibodies can be used to treat different diseases within the body. Different cells within the body have different antigens on the surface if the cells. These can be used to bind monoclonal antibodies too that contain a drug to cure the disease affected cells. This can be done with cancerous cells as they have a specific marker called a tumour marker that an antigen can bind to but not bind to any other cells except those that are cancerous. However using ,monoclonal antibodies within a human to treat disease does have disadvantage. Such as the severe side effects that have been experienced by patients who have undergone the treatment method, these include: vomiting, fever and low blood pressure.
Plant diseases and defences
Plants need mineral ions. If they do not obtain the correct amount of a mineral they suffer deficiency symptoms. Nitrates are needed for plant growth, if there is a deficiency of nitrates the plant will suffer from stunted growth. Magnesium is used to make chlorophyll which is needed for photosynthesis, if a plant is deficient of magnesium then the plan will suffer from chlorosis and have yellow leaves.
Plants can get diseases. Plants can be infected with viral, bacterial and fungal pathogens. Plants can also be infested with insects. A plant can easily be diagnosed with a pathogen as some of the usual symptoms are stunted growth, discolouration, spots on the leaves and abnormal growths. Pest infestations can also be easily diagnosed as they can usually be visually diagnosed.
Plants have physical defences: Most plant leaves and stems have a waxy cuticle, which acts as a barrier to stop pathogens entering the plant. Plant cells themselves are surrounded by cell walls made from cellulose, these form another physical barrier against pathogens. Plants have layers of dead cells around their stems, these act as another physical barrier to prevent pathogens entering the plant.
Chemical defences: Some can produce antibacterial chemicals which kill bacteria. Such as mint which produces witch hazel. Other plants produce poisons which can deter herbivores.
Mechanical defences: Some plants have adapted to have thorns and hairs which stop animals from touching and eating them. Other plants have leaves that droop and curl when something touches them, this means they can prevent themselves being consumed by passing insects or move away from things. Some plants can mimic other organisms, such as the passion flower has bright yellow spots on its leaves which look like butterfly eggs. This prevents other species of butterfly's laying eggs on the leaves.