AQA Topic 3 - Infection and Response 9-1 - Flashcards in GCSE Biology

Define a pathogen and what it causes

A pathogen is a microorganism that enters the body and causes communicable diseases

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What are bacteria and how do they make the body sick?

Bacteria are very small living cells which can reproduce rapidly in the body, they produce toxins that damage your cells and tissues which makes you feel ill

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How much smaller is a bacterium cell from a body cell?

1/100

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Describe what viruses are and what they do

Viruses are not cells and 1/100th the size of a bacterium and they reproduce rapidly

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How do viruses make you feel ill?

Viruses get inside the body cells and replicate themselves using the cell's machinery to produce multiple copies. The cell will then burst releasing all the new viruses, the cell damage is what makes you feel ill

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Define protists

Protists are single-celled eukaryotes which, as parasites, can live on or inside other organisms and cause them damage

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How are protists transferred?

Protists move via a vector - an organism which carries the protist but doesn't get the disease itself i.e an insect that carries the protist

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Describe the two different types of fungi

Some fungi are single celled whilst others have a body which is made up of hyphae (thread-like structures)

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What does hyphae fungi do?

Hyphae fungi can grow and penetrate the human skin and surface of plants causing them disease or produce spores which can be spread to other plants/animals

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Describe the 3 different ways pathogens can be spread

1. WATER - By drinking or bathing in dirty water i.e cholera 2. AIR - Pathogens spread via the air can be breathed in or inhaled by infected persons' coughs/sneezes 3. DIRECT CONTACT - Touching contaminated surfaces, including skin i.e athlete's foot

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Describe measles

Measles is a viral disease spread by droplets from an infected person's sneeze/cough. People w/ meals develop a rash/fever and can be fatal if there are complications i.e measles can lead to pneumonia (lungs) or encephalitis (brain)

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Describe HIV (1)

A virus spread by sexual contact/exchanging body fluids such as blood. It can cause flu like symptoms and can be controlled by antiretroviral drugs which stop the virus replicating. If untreated the virus can attack the immune cells to a point where

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Describe HIV (2)

the immune system can't cope with other infections or cancers, this stage is known as AIDS

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Describe TMV

Tobacco mosaic virus affects many species of plants and causes a discoloured, mosaic pattern on leaves. Because of the discolouration the plants cannot carry out photosynthesis very well so the virus affects growth

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Describe rose black spot

A fungal disease which causes purple/black spots on leaves which can turn yellow + drop off = less photosynthesis can happen = plant doesn't grow very well. It can be spread through water or wind. Can be treated by fungicides/destroying aff leaves

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Describe malaria (1)

A disease caused by a protist. Part of the malarial protist's lie cycle takes place inside the mosquito (the vector) which they get when feeding on an infected animal. As the mosquito continues to feed it affect other animals by inserting the protist

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Describe malaria (2)

into the animals blood vessels. Malaria causes repeating episodes of fever which can be fatal and the spread of malaria can be reduced by stopping mosquito reproduction. People are protected by insecticides and mosquito nets

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Describe salmonella (1)

A type of bacteria which causes food poisoning and result in stomach cramps/fever/vomiting/diarrhoea which are caused by the toxins the bacteria create. Salmonella is caught by eating contaminated food w/ the bacteria from either unhygienically

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Describe salmonella (2)

prepared meat or meat that had caught the disease when it was alive. Salmonella is controlled in the UK by a vaccination given to most poultry against it

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Describe gonorrhoea

A STD which is passed by sexual contact and caused by a bacteria. Symptoms include pain during urinating/yellow discharge from vagina/penis. To control spread people can be treated with antibiotics and use barrier methods i.e condoms

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Name 4 ways the spread of disease can be reduced/prevented

1. Being Hygienic 2. Destroying Vectors 3. Isolating Infected Individuals 4. Vaccination

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How does destroying vectors control the spread of disease?

Vectors spread the disease so without them the disease cannot be passed on. This is down via insecticides or destruction of their habitat so they can no longer breed

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Why is quarantine effective for controlling the spread of disease?

By isolating someone w/ a communicable disease it prevents them from passing it on to anyone else before they are treated

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How does the body protect itself from pathogens?

1. SKIN secretes antimicrobial substances to kill pathogens and is a barrier 2. HAIRS AND MUCUS in the nose trap particles that could contain pathogens 3. TRACHEA AND BRONCHI secrete mucus to trap pathogens 4. STOMACH produces HCl acid = kill patho's

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What is the trachea and bronchi lined with and why?

They are lined with cilia, hair-like structures which waft the mucus up to the back of the throat where it can be swallowed

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Define phagocytosis

Phagocytosis is the process of white blood cells changing shape to engulf foreign cells and digest them

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How do white blood cells destroy pathogens?

1. Consume them via phagocytosis 2. Some produce antibodies 4. Produce antitoxins

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Why do some white blood cells produce antibodies? (1)

Every pathogen has a unique molecule called an antigen on its surface, the white blood cells produce proteins called antibodies which attach onto invading cells with foreign antigens so other white blood cells can find them. These antibodies are

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Why do some white blood cells produce antibodies? (2)

specific to that type of antigen so will not lock on to others. Antibodies are then produced rapidly and carried around the body to find similar bacteria/viruses. If a person is infected with the same pathogen again the white blood cells will rapidly

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Why do some white blood cells produce antibodies? (3)

produce the antibodies to kill it so then they are naturally immune to that pathogen and won't get it

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What are white blood cells called which produce antibodies?

B-lymphocytes

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What are antitoxins?

Antitoxins are substances which counteract the toxins produced by invading bacteria

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Why are vaccinations needed?

When you're infected with a new pathogen it takes a while for your white blood cells to learn how to deal with it but in that time you can get seriously ill

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Describe the process of a vaccination (1)

You are injected with small amounts of dead/inactive/weak pathogens. These carry antigens which cause your body to produce antibodies to attack them even though the pathogen is harmless. Because the white blood cells recognise the antigens if a live

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Describe the process of a vaccination (2)

version of the same pathogen appeared then the white blood cells could produce antibodies rapidly and kill off the pathogen which means they are now immune to it

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Give the pros of vaccinations

1. Can control lots of communicable diseases that were once common i.e smallpox 2. Epidemics can be prevented if a large % of the populous are vaccinated because less people with the disease = less people to infect non-vaccinated people

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Give the cons of vaccinations

1. Vaccines don't always give you immunity 2. You can have bad reactions to them i.e swelling/fever/seizures

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What do painkillers do?

They reduce the symptoms of pathogens but don't actually kill them

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How do antibiotics work?

Antibiotics kill/prevent the growth of bacteria causing the problem w/o killing body cells. Different antibiotics kill different types of bacteria so its important to be treated with the right one

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Why can't antibiotics kill viruses?

Viruses reproduce using body cells which makes it difficult to develop drugs that destroy just the virus without killing the body's cells

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What happens if you have an infection with antibiotic resistant bacterium?

Some bacterium can be resistant to antibiotics, so when it is used only the non-resistant bacteria is killed which leaves the resistant alive which will then reproduce and the population of antibiotic resistant bacteria will increase =V bad infection

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How do we lessen the rate of development of resistant strains of bacteria?

1. Doctors avoid over-prescribing antibiotics for non serious things 2. The individual must finish the whole course of antibiotics and not just stop when feeling better

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Why can plants be useful to humans for infections?

Plants produce a variety of chemicals to defend themselves against pests/pathogens. These can be used as drugs to treat human diseases or symptoms

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Give two examples of drugs that are found from plants

1. ASPIRIN - Used as a painkiller/lower fever, developed from a chemical in willow 2. DIGITALIS - Treat heart conditions, developed from a chemical found in foxgloves

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Describe an example of a drug obtained from microorganisms

Alexander Fleming discovered a mould on one of his petri dishes which had surrounding area clear of bacteria. This mould produced a substance which killed bacteria, said substance is commonly known as Penicillin

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Describe STAGE ONE in drug testing

In preclinical testing, drugs are tested on human cells and tissues however if the drug affects whole or multiple body systems it must be done on an animal because it has an intact circulatory system

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Define efficacy of a drug

If the drug works and produces the effect you're looking for

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Describe STAGE TWO in drug testing

The next step in preclinical testing is testing the drug on live animals, this is to test: efficacy, to find its toxicity, what the best dosage is (the conc given) and how often it should be given

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What is the law in the UK about drug testing?

The new drug must be tested on two different live animals

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What are the ethical reasons against drug testing? What is the counterargument?

Some people think its cruel to test on animals but other argue its the safest way to make sure a drug isn't dangerous before given to humans

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What does the optimum dose mean in drug testing?

The dose where the drug is most effective with the least side effects

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Describe STAGE THREE in drug testing (1)

If passes preclinical then its tested on human volunteers in a clinical trial. Firstly the drug is tested on healthy volunteers to make sure there aren't any harmful side effects when the body is working normally, low doses are given initially which

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Describe STAGE THREE in drug testing (2)

gradually increase. If the results on healthy volunteers is good then the drugs can be tested on those with the illness to find the optimum dose. To test the efficiency of the drug volunteers are randomly put into two groups, one is given the drug

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Describe STAGE THREE in drug testing (3)

and the other a placebo to allow the doctor to see the actual difference the drug makes - it allows for the placebo effect

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Define a placebo in drug testing

A substance thats like the drug being tested but does not do anything, neither the patients nor administrator know who has the placebo

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What is the placebo effect?

When the patient expects the treatment to work and so feels better even though the treatment isn't doing anything

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What is the type of drug testing called?

Double-blind trials

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Why are double-blind trials used?

It allows for a) the placebo effect to be discredited b) so the doctors monitoring and analysing the results aren't subconsciously influenced by their knowledge

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When are the results of drug testing and drug trials published? why?

They are published after they've been through peer review (other scientists check the work is valid and has been carried out rigorously and abiding by the law). This is to prevent false claims

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Define monoclonal antibodies

Identical antibodies made to target one specific protein antigen

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Describe the process of making monoclonal antibodies (1)

A mouse is injected with the chosen antigen and B-lymphocytes are then taken from the mouse and fused with a tumour cell, this creates a hybridoma. The hybridoma cells divide quickly because of the tumour cell in them to produce clones that produce

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Describe the process of making monoclonal antibodies (2)

the monoclonal antibodies which can then be collected and purified

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Why are monoclonal antibodies useful?

They will only bind to a certain molecule and can bind to anything you want therefore they can be used to target a specific cell or chemical in the body

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Look at the sheet with the exam question about monoclonal antibodies in pregnancy tests

N/A

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What are tumour markers?

Antigens on cancer cell membranes that aren't found on normal body cells

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How can monoclonal antibodies be used for cancer? (1)

The monoclonal antibodies can be made to bind to the tumour markers, an anti-cancer drug (toxic, radioactive or chemical to stop the growing + dividing of the cancer) can be attracted to the monoclonal antibodies. The drug will kill the cancer cells

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How can monoclonal antibodies be used for cancer (2)

But not normal body cells near the tumour

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How are monoclonal antibodies for cancer administered to patients?

Via a drip

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Give other uses for monoclonal antibodies

1. Bind to hormones and other chemical in blood to measure their levels 2. Test blood samples in laboratories for certain pathogens

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How can monoclonal antibodies target specific molecules on a cell or in a tissue?

Monoclonal antibodies are made which will bind to the specific molecule your looking for, they are then bound to a fluorescent dye. If the molecules are present in the sample your analysing the antibodies will attach to them and be dated via the dye

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Give an advantage of monoclonal antibodies

Cancer treatment that does not affect normal body cells which makes the side effects of an antibody-based drug lower than standard chemo or radiotherapy

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Give the disadvantage of monoclonal antibodies

Have more side effects that originally expected i.e fever/vomiting which was not predicted because scientists thought because they targeted a specific thing they wouldn't create a lot of side effects which means they are not widely used

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Why are nitrates needed? What does a deficiency of nitrates cause?

Nitrates are needed to make proteins for the plant for growth, without nitrates the plant experiences stunted growth

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Why are magnesium ions needed? What does a deficiency of magnesium ions cause?

They are needed for making chlorophyll which is needed for photosynthesis. Without the Mg ions the plant suffers from chlorosis and has yellow leaves

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Name the common signs of plant illness

1. Stunted growth 2. Spots on leaves 3. Patches of decay 4. Abnormal growths i.e lumps 5. Malformed stems/leaves 6. Discolouration

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How can plant diseases be identified?

1. Look up the signs on a gardening manual/gardening website 2. Take the infected plant to a laboratory where scientists can identify the pathogen 3. Use testing kits that identify the pathogen using monoclonal antibodies

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Describe 3 physical plant defences

All are barrier methods to prevent the pathogen from entering 1. Leaves and stems have a waxy cuticle 2. Plant cells are surrounded by cell walls made from cellulose 3. Plants have layers of dead cells around their stems

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Describe 2 chemical plant defences

1. Some produce antibacterial chemical which kill bacteria i.e witch hazel 2. Others produce poisons which deter herbivores i.e foxgloves

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Describe 3 mechanical plant defences

1. Some have thorns and hairs to prevent animals touching/eating them 2. Some have leaves that droop/curl when touched which means they prevent themselves from being eaten by knocking insects off/moving away 3. Mimicry to trick others to not eat them

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Give an example of a plant that uses mimicry as a mechanical defence

The passion flower has bright yellow spots on its leaves which look like butterfly eggs, this deters other butterflies from laying their eggs there

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AQA Topic 3 - Infection and Response 9-1

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