Infection And Response Flashcards
Define the Term Pathogen
A microorganism that causes an infectious disease.
Explain how Bacteria Make us Feel Ill
-Bacterial cells are prokaryotes- single celled organisms. Bacterium cells are very small (1/100th the size of human body cells).
-Bacteria multiply extremely rapidly. Bacteria do not have to enter a cell to multiply so bacteria can easily multiply in our bloodstream and reach very large numbers very quickly.
-Many bacteria release a toxin. Toxins are chemicals which damage cells and tissues and make us feel ill.
Explain how Bacteria Make us Feel Ill
-Viruses are not cells and are about 1/100th the size of a bacterium. Unlike bacteria, viruses can only reproduce if they enter a host cell.
-Once inside a host cell, the virus uses the cells’ machinery (e.g. essential molecules) to replicate themselves many times.
-This will continue until the cell bursts open releasing the new copies of the virus. This cell damage is what causes people to feel unwell.
Explain how Protists Make us Feel Ill
-Protists are single celled eukaryotes.
-Some protists are parasites. This means they live on or inside other organisms and can cause them damage.
-They are transferred to the other organism by a vector, which doesn’t get the disease itself.
Explain how Fungi Make us Feel Ill
-Some fungi are single celled. Others have a body which is made up of a hyphae (thread like structure)
-These hyphae can grow and penetrate human skin and the surface of plants, causing disease.
-The hyphae can produce spores, which can be spread to other plants and animals.
Describe how to Prevent the Spread of Disease
Water Borne Diseases (e.g. cholera) - UV treatment, iodine tablets, sterilising the water
Air Borne Diseases (e.g. influenza) - wearing masks, keeping distance, coughing into a tissue
Diseases Spread by Direct Contact (e.g. athlete’s foot) - wash hands regularly, wipe down surfaces, avoid close contact
Diseases Spread Through Bodily Fluids (e.g. HIV) - barrier contraception, don’t use the same needles as others
Describe how to Reduce the Spread of Highly Infectious Diseases such as Ebola
-Ebola is a very highly infectious disease. It is very easily spread, unless very strict precautions are taken (for example wearing a protective suit).
-The best way to prevent the spread of diseases like this
is to isolate the patients and not allow anyone to come into contact (apart from medical staff who take precautions).
Describe how to Reduce the Spread of Pathogens for Less Infectious Diseases such as Measles
-One of the most effective ways to prevent the spread of less infectious diseases (e.g. Measles) is to vaccinate people against them.
-Because they cannot catch the disease themselves, they cannot spread it to other people.
Describe the Symptoms of Measles
-Measles is a viral disease. It can damage the breathing system and the brain.
-The first symptom of measles is a fever (high temperature). The second symptom (after three days) is a red skin rash.
Describe how Measles is Spread
-Measles is spread from person to person in droplets.
-When an infected person coughs or sneezes, tiny droplets of water are released, containing the measles virus.
-When these droplets are then inhaled by another person, the virus is passed on.
Describe the Prevention of Measles
-Measles is not very common (in the UK) as children are vaccinated against measles when they are very young.
-Neither measles nor HIV can be treated using antibiotics. This is because viruses are not killed by antibiotics
Describe the Symptoms of HIV
-HIV is a viral disease. After the initial infection with HIV, someone will experience a flu-like illness lasting one to two weeks.
-The virus will then attack cells of the immune system which becomes severely damaged.
-The patient may then catch an infectious disease e.g. TB or develop cancer. Late stage HIV / AIDS can be fatal.
Describe how HIV is Spread
-HIV is transmitted by body fluids.
-It can be transmitted through unprotected sexual intercourse (ie not using a condom) or by intravenous drug users sharing needles (which transmits infected blood).
Describe the Treatment of HIV
-Antiretroviral drugs can be taken to control HIV. These stop the virus from multiplying.
-This prevents the patient’s immune system from being damaged by the virus. The patient must take these drugs for the rest of their life.
-Neither measles nor HIV can be treated using antibiotics. This is because viruses are not killed by antibiotics
Describe the Symptoms of Salmonella
-Salmonella food poisoning is caused by bacteria.
-The symptoms of salmonella food poisoning are fever, abdominal cramps, vomiting and diarrhoea.
-When salmonella bacteria enter the human body, they release toxins. Toxins are chemicals which can damage cells.
-These toxins cause the symptoms of salmonella food poisoning.
Describe how Salmonella is Spread
-A person can become infected by ingesting food which contains salmonella bacteria (e.g. raw chicken).
-This can happen for example if raw chicken is prepared on a chopping board and then the same chopping board is not
cleaned before it is used to prepare other foods e.g. a salad.
-Any salmonella bacteria in the chicken will be killed when it is cooked.
-However, the salmonella bacteria which have contaminated the salad will not be killed and can cause salmonella food poisoning
Describe the Prevention of Salmonella
-To prevent salmonella, wash hands and keep uncooked meat away from other foods.
-Salmonella food poisoning is uncommon in the UK as all chickens are vaccinated against the bacteria which cause salmonella.
Describe the Symptoms of Gonorrhoea
-Gonorrhoea a sexually transmitted disease (STD) caused by a bacterium.
-It is passed on by sexual contact e.g. having unprotected sex caused by bacterium.
-The symptoms of gonorrhoea are a yellow/green discharge from the penis or vagina.
-Gonorrhoea can also lead to pain when urinating.
Describe the Treatment of Gonorrhoea
-Gonorrhoea is treated using antibiotics. However, it is no longer treated with the antibiotic penicillin.
-This is because the bacteria have become resistant to penicillin.
-This means is that the bacteria have changed so they are no longer killed by penicillin.
Describe the Prevention of Gonorrhoea
-One way of preventing the spread of gonorrhoea is to use a condom during sexual intercourse. This prevents the bacterium from passing from one person to another.
-Another way of preventing the spread of gonorrhoea is to test people who have had unprotected sexual intercourse (and are therefore possibly infected with gonorrhoea).
-If a person is found to be positive for gonorrhoea, they
should be given antibiotics to kill the bacteria.
Describe how Malaria is Spread
-Malaria is a communicable disease caused by a protist.
-However, unlike many other diseases, malaria cannot be passed directly from person to person. Instead, the malaria pathogen is spread via mosquitoes.
-First the mosquito bites an infected person. Blood and the malaria pathogen pass into the mosquito.
-The mosquito then bites an uninfected person, passing on the pathogen.
-Because the mosquito carries the pathogen from one person to another, scientists call it a vector.
Describe how Stooping the Vector from Breeding can Prevent the Spread of Malaria
-Mosquitoes prefer to breed in areas of still water.
-To stop this, people can find areas of still water and drain them. This includes ponds and swamps. They can also spray areas of still water with insecticides to kill the mosquitoes.
-However, these methods have not been fully successful in preventing malaria. This is because it is virtually impossible to find every single area of still water.
Describe how Mosquito Nets can be Used to Prevent the Spread of Malaria
-One way to reduce the spread of malaria is to prevent mosquitoes from biting people.
-Many people are bitten while they sleep so to prevent that, they should sleep under a mosquito net.
-Because mosquitoes cannot penetrate the net, they cannot bite the person sleeping.
-If we soak the mosquito net in insecticide, then any mosquito which lands on the net will also be killed.
Describe how Tobacco Mosaic Virus Affects Plants
-Tobacco mosaic virus is a virus and is not specific to one plant. It is spread through the contact of diseased plant material and insects.
-When plants are infected with TMV, their leaves develop a patchy discolouration. Patches of the leaves have less chlorophyll that normal.
-This means that the rate of photosynthesis is lower than it should be. Because the plant is photosynthesising less than it normally would, the plant grows more slowly.
-It can be prevented by growing resistant strains of plants.
Describe how Rose Black Spot Affects Plants
-Rose black spot is a communicable plant disease which is caused by a fungus. This is spread from plant to plant via water or the wind.
-When a plant becomes infected, the leaves develop spots which are black or purple. Eventually, infected leaves turn yellow and fall off the plant.
-This causes the plant to have a reduced rate of photosynthesis. Because of this, plants which are infected with rose black spot will grow more slowly than plants which are not infected.
-We can treat infected plants by removing infected leaves and destroying them so that the fungus can’t spread to other plants. We can also spray the plant with fungicides.
Describe how the Skin Forms a Layer of Protection Against Pathogens
-The outer part of the skin consists of a layer of dead skin cells. This is a thick barrier which is difficult for pathogens to
penetrate.
-The skin is also covered in a layer of sebum which can kill bacteria.
-If the skin is damaged then pathogens can enter. To prevent this, the damaged area rapidly forms a scab to block the entry of pathogens.
Describe how the Respiratory System Prevents the Entry of Pathogens
-The interior of the nose is covered with hairs and mucus. These trap pathogens that are breathed in, before they can pass down into the lungs.
-The trachea and bronchi are covered in cilia. Cilia are tiny hairs which line the surface of the trachea and bronchi. The cilia are covered with a thin layer of mucus.
-When we inhale pathogens, they stick to the mucus. The cilia then waft the mucus upwards towards the throat, where the mucus is swallowed into the stomach.
Describe how the Digestive System Prevents the Entry of Pathogens
-The mouth contains helpful bacteria that get rid of pathogens. Saliva also helps to remove unfriendly bacteria and clean the mouth.
-The stomach contains hydrochloric acid which kills any pathogens that enter on our food.
-The large intestine contains friendly bacteria that stops pathogens from growing.
