GCSE AQA Biology - Topic 3 - INFECTION AND RESPONSE Flashcards
What are pathogens?
Microorganisms that enter the body and cause disease
What type of diseases do pathogens cause?
Communicable (infections) diseases, that can easily spread
What can pathogens affect?
Both plants and animals
What are bacteria?
Very small cells which can reproduce rapidly inside your body
What can bacteria do?
Make you feel ill by producing toxins that damage your cells and tissues
What are viruses?
They are not cells, they’re tiny 1/100th the size of bacterium and they reproduce rapidly inside your body
What do viruses do?
Live inside your cells and replicate themselves using the cells machinery to produce many copies of themselves, this cell will then burst releasing all the new viruses
What about a virus makes you feel ill?
The cell damge
What are protists?
They are mostly single-celled eukaryotes, some are parasites, they are often transferred to the organism through a vector
What is a parasite?
They live in or on other organisms and can cause them damage
What is a vector?
An insect that carries the protist
What can fungi be?
Single-celled or have a body which is made up of hyphae
What are hyphae?
Thread-like structures
What do hyphae do?
Grow and penetrate human skin and the surface of plants, causing diseases
What three ways can pathogens be spread?
Water, Air, Direct Contact
How are pathogens spread through water?
They can be picked up by drinking or bathing in dirty water e.g. cholera
What is cholera?
A bacterial infection that’s spread by drinking water contaminated with diarrhoea of other sufferers
How are pathogens spread by air?
They can be carried in the air and then breathed in, some air born pathogens are carried in the air by droplets produced when you cough or sneeze
What is an example of a pathogen spread by air?
The influenza virus
How are pathogens spread by direct contact?
They can be picked up by touching contaminated surfaces, including the skin e.g. athletes foot
What is athletes foot?
A fungus which makes the skin itch and flake off, it is most commonly spread by touching the same thing as the infected person e.g. shower floors or towels
What are the three viral diseases you need to know about?
Measles, HIV, and Tobacco mosaic virus (TMV)
How is measles spread?
Through droplets of an infected persons cough or sneeze
What do people with measles develop?
A red skin rash and a sign of a fever
What can happen if there are complications with measles?
It can be very serious or even fatal, for example it can sometimes lead to pneumonia or a brain infection called encephalitis
When are most people vaccinated against measles?
When they are young
What is HIV?
A virus spread by sexual contact or exchanging bodily fluids such as blood, this can happen when people share needles when taking drugs
What are the symptoms of HIV?
Initially flu-like symptoms for weeks, usually the person doesn’t experience any symptoms for several years
What can HIV be controlled?
Through antiretroviral drugs which stop the virus replicating
What does the HIV virus do?
Attack immune cells, if the body’s immune system is badly damaged, it can’t cope with other infections or cancers.
What is the stage in HIV when your immune system is severely damaged?
Late stage HIV infection or AIDS
What is tobacco mosaic virus (TMV)?
A virus that affects the growth of many species of plants e.g. tomatoes
What does TMV cause?
A mosaic pattern on the leaves of plants, parts of it become discoloured. This means that the plants can’t carry out photosynthesis very well
What is a fungal disease that you need to know?
Rose black spot
What is rose black spot?
A fungus that causes black or purple spots to develop on the leaves of rose plants, the leaves can then turn yellow and drop off, this means less photosynthesis can happen
How does black rose spot spread?
Through the environment e.g. water or wind
How can gardeners treat black rose spot?
Using fungicides and by stripping the plant of its affected leaves, the leaves then need to be destroyed so that fungus can’t spread to other rose plants
What is a disease caused by a protist?
Malaria
Where does part of malarial protist’s life take place?
Inside a mosquito, they are vectors. They pick up the malarial protist when feeding on other infected animals
What happens every time the vector mosquito feeds on another animal?
It passes the malarial disease onto that animal by inserting the protist into the animals bloodstream
What does malaria cause?
Repeating episodes of fever and can be fatal
How can the spread of malaria be reduced?
Reducing mosquitos ability to breed, insecticides and mosquito nets
What two bacterial diseases do you need to know about?
Salmonella and Gonorrhoea
What is salmonella?
A type of bacteria that causes food poisoning
What are the symptoms of salmonella?
Fever, stomach cramps, vomiting, diarrhoea, caused by the toxins the bacteria produce
How can you get salmonella?
Eating food contaminated with salmonella e.g. raw chicken
What do they do in UK to help decrease salmonella?
Vaccinate most poultry
What is gonorrhoea?
A sexually transmitted disease (STD) cause by bacteria
How are STDs passed on to others?
By sexual contact e.g. having unprotected sex
What are the symptoms of gonorrhoea?
Pain whilst urinating, thick yellow or green discharge from the vagina or the penis
How was gonorrhoea originally treated?
With penicillin, but it has become trickier now as the bacteria has become resistant to it
How do we treat gonorrhoea?
Antibiotics and should use barrier methods of contraception e.g. condoms
What can you do to reduce of prevent the spread of disease?
Being hygienic, destroying vectors, isolating infected individuals, vaccination
What features do the body have as a defence system?
The skin, hair and mucus, trachea and bronchi, cilia, stomach
How does the skin act as a defence mechanism?
A barrier to pathogens and it secretes antimicrobial substances which kill pathogens
How does hair and mucus work as a defence system?
They are in your nose and trap particles that could contain pathogens
How the trachea and bronchi act as defence systems?
They secrete mucus to trap pathogens
Where on the cilia?
They are lined in the trachea and bronchi
How does cilia work as a defence system?
The hair-like structures waft the mucus up to the back of the throat where it can be swallowed
How does the stomach work as a defence mechanism?
It produces hydrochloric acid which kills any pathogens that make it past the mouth
What happens if pathogens do make it into your body?
Your immune system kicks in to destroy them
What is the most important part of your immune system?
The white blood cells, they travel around your blood constantly patrolling for microbes. When they come across one they have three forms of attack
What are the white blood cells three forms of attack,
Consuming them, producing antibodies or producing antitoxins
What is it called when a white blood cell engulf foreign cells and digest them?
Phagocytosis
What does every pathogen have on its surface?
Unique molecules called antigens
What happens when some types of white blood cell comes across a foreign antigen?
They will start to produce proteins called antibodies to lock onto the invading cells so that type of antigen - they won’t lock on to any others
What happens when the correct antibody is found?
Antibodies are then produced rapidly and carried around the body to find all similar bacteria or viruses
What happens if someone is infected with the same pathogen a second time?
The white blood cells remember the antibody needed and rapidly produce them to kill it - the person is naturally immune to that pathogen and won’t get ill
What do the white blood cells antitoxins do?
Counteract the toxins produced by the invading bacteria
How long does it take for your body to fight a new pathogen?
It takes the white blood cells a few days to learn how to deal with, but by that time you can be pretty ill
What are vaccinations?
It involves injecting small amounts of dead or inactive pathogens, these cart antigens which cause your body to attack them even though the pathogen is harmless (dead or inactive) so that when they get the actual disease it can be fought off immediately
What does the MMR vaccine contains?
Weakened versions of the viruses that cause measles, mumps and rubella all in one vaccine
What are the pros of vaccinations?
-They have helped control lots of communicable diseases that were once common in the UK (smallpox has been eradicated) -Epidemics have been prevented if a large percentage of the population is vaccinated
What are the cons of vaccines?
-They don’t always work, sometimes they don’t give you immunity -You can sometimes have a bad reaction to a vaccine (e.g. swelling or maybe something more serious like fever or seizures)
What are painkillers?
Drugs that relieve pain however don’t actually tackle the cause of the disease or kill pathogens, they just help to reduce the symptoms
What is an example of a painkiller?
Aspirin
What are antibiotics?
Drugs that actually kill or prevent the growth of the bacteria causing the problem without killing your own body cells, however they don’t destroy viruses
Why is it difficult to destroy viruses?
Because they reproduce using your body cells so it is difficult to destroy them without harming your body cells
What is an example of an antibiotic?
Penicillin
How can bacteria become resistant to antibiotics?
They can mutate and so the ones that are resistant will be left behind and continue to survive and reproduce (e.g. MRSA)
How do doctors slow down the rate of development of resistant strains?
Only prescribe antibiotics for more serious diseases
What drugs have come from plants?
Aspirin and Digitalis
What is aspirin?
It is used as a painkiller and to lower a fever, it was developed from a chemical found in a willow
What is digitalis?
A drug used to treat heart conditions which is developed from a chemical found in foxgloves
What is a drug extracted from microorganisms?
penicillin
How did Alexander Fleming discover penicillin?
He was clearing out some petit dishes containing bacteria and noticed one had a strange mould on it and he area around it was free of bacteria
What are the three main stages in drug testing?
Testing on human cells and tissues, testing in love animals, tested on human volunteers in a clinical trial
What happens in stage 1 of drug testing?
Human cells and tissues are tested on, however you can’t use them for drugs that affect whole or multiple body systems e.g. testing a drug for blood pressure
What happens in stage 2 of drug testing?
Animal testing, to test the drugs efficacy, to find its toxicity and to find the best dosage
What is the law in Britain on animal testing?
Any new drug must be tested on two different live mammals, some people think it is cruel to test on animals but others believe this is the safest way to make sure a drug isn’t dangerous before given to humans
What is the third step of drug testing?
-First the drug is tested on healthy volunteers to make sure it doesn’t have any harmful side effects when the body is working normally -They then test it on people suffering from the illness, the optimum dose is found -There are two groups one is the new drug and other is a placebo, clinical trials are blind -The results are not confirmed
What are antibodies produced by?
B-lymphocytes- a type of white blood cell
What are monoclonal antibodies?
Identical antibodies
What are monoclonal antibodies produced from?
Lots of clones of single white blood cell, this means all the antibodies are identical and will only target one specific antigen
Why can’t you just grab the lymphocyte that made the antibody and produce more?
Lymphocytes don’t divide very easily
What is a hybridoma?
A cell made from the fusion of a mouse b-lymphocyte with a tumour cell
What do tumour cells do?
Don’t produce antibodies and so grow really quickly
What can hybridoma cloned to do?
To get lots of identical cells, these produce the antibodies (monoclonal antibodies), these antibodies can be collected and purified
Why are monoclonal antibodies useful?
They can bind to anything you want e.g. an antigen that’s only found on the surface of one type of cell, so you can use them to target specific things
What can monoclonal antibodies be used for?
In pregnancy tests, to treat diseases and to find specific substances in research
How are monoclonal antibodies used in pregnancy tests?
-The stick you wee on has some antibodies to the hormone, with blue beads attached -The test strip has some more antibodies to the hormone stuck to it
What happens to the pregnancy test if you are pregnant?
The hormone binds to the antibodies on the blue beads, the urine then moves up the stick, carrying the hormone and the beads. The beads and hormone bind to the antibodies on the strip so the blue bead gets stuck to the strip turning it blue
What hormone do you produce when pregnant?
HCG
What happens to a pregnancy test when you are not pregnant?
The urine still moves up the stick, carrying the blue beads but there is nothing for it to stick to so it does not turn blue
What are tumour markers?
The antigens on cancer cells cell membranes that are not found on normal body cells
