Topic 3 - Infection and Response Flashcards
What are pathogens?
Microorganisms that enter the body and cause communicable diseases
Can pathogens only infect animals?
No they can infect plants too
What are the different pathogens?
Bacteria
Viruses
Protists
Fungi
What are bacteria?
Very small cells about 1/100 th the size of our body cells.
How do bacteria make us feel ill?
By producing toxins that damage your cells and tissues. They reproduce rapidly in the body
What are viruses?
They are not cells. They are about 1/100 th the size of bacterium.
How do viruses make us feel ill?
They live inside your cells and use the cells machinery to produce many copies of themselves, the cell will burst, releasing all the new viruses. The cell damage is what makes you feel ill
What are protists?
They are eukaryotes and most of them are single-celled. Some are parasites.
What do parasites do?
Live on it inside other organisms and can cause them damage, they are often transferred to the organisms via a vector which doesn’t get the disease itself.
What are fungi?
Some are single-celled. Others have bodies made of hyphae (thread like structures)
How do fungi make us feel ill?
Hyphae from the fungi can grow and penetrate human skin and the surface of plants, causing disease. Hyphae can produce spores which can be spread to other plants and animals.
How do pathogens spread?
Water
Air
Direct contact
How do pathogens spread through water?
Some can be picked up by drinking and bathing in dirty water. E.g. cholera is a bacterial infection that’s spread by water contaminated with diarrhoea from other sufferers
How do pathogens spread through air?
They can be breathed in through the air. Some are carried in air born droplets produced when you cough or sneeze. E.g. the influenza spreads this way.
How do pathogens spread through direct contact?
Some pathogens can be picked up by touching contaminated surfaces, including the skin. E.g. athletes foot is a fungus which makes skin itch and flake off, most commonly spread by touching the same things as the contaminated
What are 3 viral diseases that we need to know?
Measles
HIV
tobacco mosaic virus (TMV)
How is measles spread?
By droplets from an infected cough or sneeze
What is measles?
Red skin rash and signs of fever. It can be very serious and even fatal if there are complications. Most people are vaccinated against measles when they are young
What are the complications of measles?
Pneumonia (lung infection)
Encephalitis (brain infection)
How is HIV spread?
Sexual contact or by exchanging bodily fluids like blood, this can happen when people share needles when taking drugs
What are the symptoms of HIV?
Flu- like symptoms for a few weeks, then no symptoms for several years. Viruses attack immune cells, if the body’s immune system is badly damaged it can’t cope with other infections or cancers. At this point it has become AIDS
How can HIV be treated?
When there are no symptoms for years during this time HIV can be controlled with antiretroviral drugs which stop the viruses replicating
What is tobacco mosaic virus?
A virus that affects many species of plants, it causes a mosaic pattern on the leaves of the plants, parts of the leaves become discoloured. Discolouration means less photosynthesis so the virus affects growth
what is rose black spot?
a fungus that causes purple or black spots to form on the leaves of rose plants, less photosynthesis can happen so the plant doesn’t grow very well
how does rose black spread?
though the environment in water or by the wind
how can rose black spot be treated?
gardeners can treat the disease using fungicides and by stripping the plant of its affected leaves, these leaves then need to be destroyed so that the fungus an’t spread
what is malaria?
its caused by a protist, mosquitoes are vectors when they pick it up from feeding on infected animals. whenever the mosquitoes feed on another animal they insert the protist into the animal’s blood vessels
what are the symptoms of malaria?
it causes repeating episodes of fever, it can be fatal
how can malaria be prevented?
the spread of malaria can be reduced by stopping the mosquitoes from breeding. people can be protected using insecticides, mosquito nets and being vaccinated against it
what are 2 bacterial diseases?
salmonella
gonorrhoea
what is salmonella?
its a type of bacteria causes food poisoning
what are the symptoms of salmonella?
fever, stomach cramps, vomiting and diarrhoea. these symptoms are caused by toxins that the bacteria produce
how do people get salmonella?
eating food thats been contaminated with salmonella bacteria, e.g. eating chicken that was contaminated whilst it was alive, or food prepared in unhygienic conditions
how can salmonella be prevented?
in the UK, most poultry is given a vaccination against salmonella, this is to control the spread of the disease
what is gonorrhoea?
it is a sexually transmitted disease, which is spread through sexual contract, and is caused by bacteria
what are the symptoms of gonorrhoea?
pain when urinating, thick yellow / green discharge from the penis or vagina
how can gonorrhoea be treated?
it was originally treated with an antibiotic called penicillin, but this is trickier because certain strains have become resistant. to prevent the spread people can be treated with antibiotics and should use barrier methods of contraception such as condoms
what can be done to reduce and prevent the spread of disease?
being hygienic
destroying vectors
isolating infected individuals
vaccination
how can being hygienic reduce the spread of disease?
using simple hygiene measures can prevent the spread of disease. e.g. washing hands thoroughly before preparing food after you have sneezed can stop you infecting another person
how can destroying reduce the spread of disease?
by getting rid of the organisms that spread disease, you can prevent the disease from spreading. insect vectors can be destroyed with insecticides or destroying habitats so they can’t breed
how can isolating infected individuals reduce the spread of disease?
if you isolate someone with a communicable disease, it prevents them from passing it on to anyone else
how can vaccination reduce the spread of disease?
vaccinating people and animals means they can’t develop the disease and pass it on to someone else
what defends the body against disease?
skin tears earwax mucus stomach acid if none of these work the immune system kicks in
how can skin defend us against disease?
it acts as a barrier against pathogens. it also secretes antimicrobial substances which kill pathogens
how can tears defend us against disease?
they contain the lysozyme enzyme to kill bacteria
how can earwax defend us against disease?
it kills bacteria
how can mucus defend us against disease?
hairs and mucus in your nose trap particles that could contain pathogens. the trachea and bronchi secrete mucus to trap pathogens
how can stomach acid defend us against disease?
the trachea and bronchi are lined with cilia which waft the mucus up to the back of the throat where it can be swallowed. the stomach produces hydrochloric acid, which kills pathogens
what is the most important part of your immune system?
white blood cells, they travel in your blood and look for microbes, when they come across an invading microbe they have 3 lines of defence
what are the white blood cells 3 lines of defence?
consuming microbes
producing antibodies
producing antitoxins
how do white blood cells consume?
white blood cells can engulf foreign cells and digest them, this is called phagocytosis
why do white blood cells produce antibodies?
every pathogen has unique molecules on its surface called antigens. when b-lymphocytes come across foreign antigen, they will produce antibodies which are specific to that type of antigen, to lock onto the invading cells so that they can be found and destroyed by other white blood cells
what do antibodies do after they are produced?
they are produced rapidly and carried around the body to find all similar bacteria or viruses
what happens if reinfection from a pathogen occurs?
white blood cells will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen and won’t get ill
what do antitoxins do?
these counteract toxins produced by the invading bacteria
what happens when you are infected with a new pathogen?
it takes a while for you white blood cells to learn how to deal with it, by that time you are already ill
what do vaccinations involve?
injecting small amounts of dead or inactive pathogens, which carry antigens which cause your body to produce antibodies to attack them even though the pathogen is harmless. e.g. MMR vaccine contains weakened versions of the viruses that cause measles, mumps and rubella
what are the pros of vaccines?
they have helped control lots of communicable diseases that used to be common. epidemics can be prevented if a large % of the population are vaccinated because there are less people to catch and spread the disease
what are the cons of vaccination?
they don’t always work, sometimes they don’t give immunity
some people have bad reactions (swelling, fevers or seizures), but this is very rare.
what are pain killers?
they are drugs that relieve pain, but don’t tackle the cause of the disease or kill pathogens, they just reduce symptoms.
how are antibiotics different to pain killers?
they actually kill or prevent the growth of bacteria without killing your own body cells. different antibiotics kill different types of bacteria, so its important to be treated with the right one. the use of antibiotics has greatly reduced the number of deaths from communicable disease caused by bacteria
do antibiotics kill viruses?
NO, antibiotics don’t destroy viruses because they use your body cells to reproduce, which makes it difficult to develop drugs that destroy the virus without harming body cells
how do bacteria become resistant?
they can mutate and sometimes the mutations cause them to become resistant to an antibiotic
what happens when you are infected with antibiotic resistant bacteria?
when you treat the infection, only the non-resistant strains will be killed, the resistant bacteria will survive and reproduce, so the population will increase, this is natural selection. this resistant strain could cause a serious infection that can’t be treated with antibiotics
what are examples of resistant bacteria?
MRSA
super gonorrhoea
how can the development of resistant bacteria be slowed down?
doctors should avoid over-prescribing antibiotics and for patients to to finish the whole course of antibiotics and don’t just stop when you feel better
how did most drugs come from plants?
they produce a variety of chemicals to defend themselves against pests and pathogens. some of them can be used as drugs to treat human disease or relieve symptoms
what is aspirin and where did it come from?
it is used as a painkiller and to lower fever. it was developed from a chemical in willow bark
what is digitalis and where is it found?
it’s used to treat heart conditions. it was developed from a chemical found in fox gloves
who discovered penicillin?
Alexander Fleming
how was penicillin discovered?
Fleming was clearing out some Petri dishes containing bacteria, he noticed one dish also had mould on it and the area around the mould was free of bacteria. the mould was producing a substance that killed the bacteria (penicillin)
what is a monoclonal antibody?
antibodies that will bind to specific cells in the body, because different cells have different antigens
what are tumour markers?
antigens found on cancer cell, cell membranes that aren’t found on normal body cells
how can monoclonal antibodies treat cancer?
in the lab, you can make anti-cancer drugs attached to monoclonal antibodies bind to tumour markers. this might be a radioactive substance, a toxic drug or a chemical which stops cancer cells from growing and dividing
how does the monoclonal antibody transport drugs to cancer cells?
the antibodies are given to a patient through a drip. they target specific cells because they only bind to tumour markers. the drug kills the cancer cells but doesn’t kill any body cells near the tumour
what can monoclonal antibodies be used to do?
bind with hormones and other chemicals in the blood to measure their levels
test blood samples in laboratories for certain pathogens
locate specific molecules on a cell or in a tissue
how can monoclonal antibodies locate specific molecules?
monoclonal antibodies are made for the specific molecules your looking for
they are then bound to a fluorescent dye
if the molecules are present in a sample being tested, the monoclonal antibodies will attach to them and can be detected using the dye
what are the advantages of monoclonal antibodies?
cancer treatment - chemotherapy and radio therapy, etc. can affect normal body cells but monoclonal target specific cells, so the side effects are lower
what are the disadvantages of monoclonal antibodies?
scientist thought there wouldn’t be many side effects because they target specific cells but they can cause fever, vomiting, and low blood pressure. so they are not as widely used as was originally thought
What happens if plants don’t get enough mineral ions?
Plants need mineral ions from the soil. If there aren’t enough they suffer deficiency symptoms
What mineral ions do plants need?
Nitrates
Magnesium ions
Why do plants need nitrates?
To make proteins and therefore for growth. A lack of nitrates causes stunted growth
Why do plants need mineral ions?
For making chlorophyll, so for photosynthesis. Plants without enough suffer from chlorosis and have yellow leaves.
What can infect plants?
Viral, bacterial and fungal pathogens. They can be infested and damaged by insects. E.g. aphids are insects that cause huge damage to plants.
What are the signs that a plant is diseased?
Stunted growth Abnormal growth Spots on the leaves Malformed stems or leaves Patches of decay Discolouration
How can plant diseases be identified?
Looking up symptoms in a gardening manual or website
Taking the infected plant to a lab where scientists can identify the pathogen
Using testing kits that identify the pathogens using monoclonal antibodies
What are the 3 different types of defences plants have?
Physical
Chemical
Mechanical
What are a plants physical defences?
Most leaves and stems have a waxy cuticle which defends against pathogens
Plants cells are surrounded by cell walls made of cellulose, this is a physical barrier for pathogens that pass the waxy cuticle.
They have layers of dead cells around their stems that act as a barrier
What are plants chemical defences ?
Some produce antibacterial chemicals which kill bacteria e.g. the mint plant and witch hazel
Others produce poisons which can deter herbivores e.g. tobacco plants, foxgloves and deadly nightshade
What are a plants mechanical defences?
Some adapted with thorns and hairs, which stop animals touching and eating them
Some have leaves that drop or cool when touched, so they knock insects off themselves and move away from things
Some plants mimic other organisms e.g. the Passion flower has spots that look like butterfly eggs so butterflies don’t eat them, some stones in South Africa look like stones so they don’t get eaten
What are the 3 stages of drug testing?
Preclinical- human cells and tissues
Preclinical- live animals
Clinical - human volunteers
Why is testing drugs on human cells and tissues not the best way?
You can’t use human cells and tissues to test drugs that affect a whole or multiple body systems e.g. drugs for blood pressure need a circulatory system
Why do we test drugs on live animals?
For efficacy, to find out about its toxicity and to find the best dosage
What is efficacy?
Whether the drug works and produces the effect you’re looking for
What’s toxicity?
How harmful the drug is
What’s best dosage?
The concentration of the drug that should be given, and how often it should be given
What are the laws about drug testing?
The law in Britain states any new drug must be tested on at least 3 different live animals. Some people think this is cruel, but others believe it is the safest way to make sure a drug isn’t dangerous before it’s given to humans
What is a clinical trial?
The drug is tested in healthy volunteers. At the start of the trial a very low dose is given and is gradually increased.
Then it’s tested on people who suffer from the illness in a double blind trial, the optimum dose is found.
The results aren’t published until they e been through peer review which helps prevent false claims
Why is a drug tested in healthy volunteers first?
To make sure that it doesn’t have any harmful side effects when the body is working normally
What is the optimum dose?
The dose of a drug that is the most effective with the least side effects
What is a double blind trial?
Patients are randomly split into 2 groups, one is given the real drug and the other is given a placebo (so the doctor can actually see the difference the drug makes). When they are double blind it means neither patients nor doctor knows who has the placebo until the results are gathered so they can’t subconsciously affect the results
How are monoclonal antibodies produced?
They are produced from lots of clones of a single white blood cell, so they are identical and will only target 1 specific protein antigen
Why isn’t producing lots of clones of a white blood cell easy?
Lymphocytes don’t divide very easily. Tumour cells don’t produce antibodies but they can be grown very easily.
How can B-lymphocytes be mass produced?
A mouse is injected with the antigen of the desired pathogen, B-lymphocytes produced by the mouse in response to the pathogen are extracted and fused with a tumour cell. This is called a hybridoma
What can hybridoma cells do?
They can be cloned to get lots of identical cells that produce monoclonal antibodies which can be collected and purified
Why are monoclonal antibodies really useful?
You can make monoclonal antibodies that bind to anything, like an antigen only find on the surface of 1 type f cell and will only target this molecule. So you can target a specific cell or chemical in the body.
What do pregnancy testing strips detect?
A hormone called HCG which is found in the urine of pregnant women
How do pregnancy test work?
The bit where you were on had antibodies that attach to the hormone with blue beads attached.
The test strip has more of the antibodies stuck onto it.
If you’re pregnant the test strip goes blue
What happens in a pregnancy stick if you’re pregnant?
The hormone bonds to the antibodies on the blue beads.
The urine moves up to the test strip with the hormone and the beads which bind to the antibodies stuck there.
The blue beads turn the strip blue
