Topic 3 - Infection and Response

Question 1

Outline bacteria

Answer 1

Very small cells which can rapidly reproduce in your body they make you feel ill by producing toxins that damage your cells and tissues

Question 2

Outline viruses

Answer 2

Not cells they’re tiny and reproduce rapidly in your body and replicate themselves using the cells’ machinery to produce copies of themselves, eventually the cell will burst releasing all the viruses and the cell damage will make you feel ill

Question 3

Outline protists

Answer 3

Lots of different types of protists but they’re all eukaryotic and most are single celled
Some are parasites which live on or inside other organisms and can cause them damage. Often transferred to the organism by a vector which doesn’t get the disease itself

Question 4

Outline fungi

Answer 4

Some are single celled others have a body made up of hyphae which can grow and penetrate the human skin and surface of plants causing disease
Hyphae can produce spores which can be spread to other animals and plants

Question 5

Define pathogens

Answer 5

Microorganisms that enter the body and cause communicable diseases that can easily spread
Both animals and plant can be infected by pathogens

Question 6

How can pathogens be spread

Answer 6

1. Water - Pahtogens can be picked up through water you bathe in or drink (e.g. cholera)
2. Air - pathogens can be carried through the air and breathed in. Some airborne pathogens can be carried in droplets when you cough or sneeze (e.g. influenza)
3. Contact - Some can be picked up by touching contaminated surfaces including the skin (e.g. athletes foot)

Question 7

Outline the measles

Answer 7

-A virus that is spread by droplets from an infected persons sneeze or cough
-People with it develop a red skin rash and they’ll show signs of a fever
-It can be serious or even fatal if there are complications for example sometimes it can lead to pneumonia or inflammation of the brain
-Most people are vaccinated against it when they are young

Question 8

Outline HIV

Answer 8

-A viral disease spread through exchanging bodily fluids during sexual inter course or using needles when taking drugs
-Initially causes flu-like symptoms for a few weeks and the person usually doesn’t experience any more symptoms for years. During this time the HIV can be controlled with antiretroviral drugs stopping the virus replicating in the body
-The virus attacks the cells and if the immune system is bad,t damaged it can’t cope with other infections or cancer - this is called AIDS

Question 9

Outline tobacco mosaic virus

Answer 9

-It is a virus that infects plants like tomato’s
-It causes a mosaic pattern on the leaves of the plant and some parts become discoloured
-The discolouration means that the plant can’t carry out photosynthesis as well so the virus affects growth

Question 10

Outline rose black spot

Answer 10

-A fungus that causes black or purple spot to develop of the leaves of rose plants, the leaves can turn yellow and drop off
-Less photosynthesis can happen and because less glucose, cellulose and proteins are made the plant has less energy so it doesn’t grow very well
-It spreads through the environment in water or by the wind
-Gardeners can treat the disease using fungicides and by stripping the plant or its affected leaved. These leaves then need to be destroyed so the fungus can spread to other plants

Question 11

Outline malaria

Answer 11

-Caused by a protist’s and part of its life cycle takes place inside a mosquito which are the vectors and they pick it up when they feed on an infected animals
-Every time a mosquito feeds on another animal it infects it by inserting the protist into animals blood vessels
-Causes repeating episodes of fever and it can be fatal
-Can be reduced by stopping the mosquitoes from breeding
-People can be protected by using insecticides and mosquito nets

Question 12

Outline salmonella

Answer 12

-A type of bacteria that causes food poisoning
-Infected people can suffer from fever, cramps, vomiting and diarrhoea
-Caused by the toxins that the bacteria produce
-You can get salmonella poisoning from eating contaminated food (e.g. chicken that caught it) or eating food prepared in unhygienic conditions
-In UK most poultry is given a vaccine against salmonella to control the spread of the disease

Question 13

Outline gonorrhoea

Answer 13

-A bacterial STD that gives infected people pain whilst urinating and thick green or yellow discharge from the vagina or the penis
-Originally treated by penicillin but has become trickier as some strains have become resistant
-To prevent the spread of gonorrhoea, people can be treated with antibiotics and should use barrier methods of contraception such as condoms

Question 14

How does the skin act as a defence system for the body

Answer 14

It is a barrier to pathogens and secretes antimicrobial substances which kill them

Question 15

How does your nose act as a defence system for the body

Answer 15

Mucus and hair in your nose trap particles that could contain pathogens

Question 16

How do the trachea and bronchi act as a defence system for the body

Answer 16

-Secrete mucus to trap pathogens
-Also lined with cilia which are hair like structures which waft the mucus up to the back of the throat where it can be swallowed

Question 17

How does the stomach act as a defence system for the body

Answer 17

Produces hydrochloric acid which can kill pathogens that make it there from the mouth

Question 18

How do white blood cells defend your body against pahtogens

Answer 18

1. Consuming them by engulfing and digesting them - phagocytosis
2. -When they come across a foreign antigen they will produce proteins called anti bodies to lock onto the invading cells so they can be found and destroyed by other white blood cells. -Antibodies are specific to that type of antigen and won’t lock onto any others
   -Antibodies are then produced rapidly and carried around the body to find all similar bacteria or viruses
   - If the person is infected with the same pathogen again the white blood cells will rapidly produce the antibodies to kill it and the person is naturally immune and won’t get it
3. Produce antitoxins which counter the toxins produced by the invading bacteria

Question 19

What are vaccinations

Answer 19

-Injecting small amounts of dead or inactive pathogens which carry antigens which your body produces antibodies to attack them even thought it is harmless. For example the MMR vaccine contained weakened versions of the viruses that causes measles, mumps and rubella in one vaccine
-If live pathogens of the same type appear after that the white blood cells can rapidly mass-produce antibodies to kill if the pathogen

Question 20

Advantages of vaccination

Answer 20

-Helped control lots of communicable diseases that were once common in the U.K.
-Bug outbreaks of disease can be prevented if a large portion of the population is vaccinated and even people who aren’t vaccinated are unlikely to catch the disease as there are fewer people able to pass it on. A significant number of people aren’t vaccinated the disease can spread quickly through them and lots will be i’ll at the same time

Question 21

Disadvantage of vaccines

Answer 21

-Don’t always work and give you immunity
-Can have bad reactions to vaccines (e.g. swelling or more seriously seizures or fevers)

Question 22

Outline painkillers

Answer 22

For example aspirin are drugs that relieve pain but don’t tackle the causes of disease or kill the pathogen just reduce the symptoms

Question 23

How do antibiotics work

Answer 23

They kill or prevent the growth of bacteria causing the problem without killing your own body cells and different ones kill specific types of bacteria so it has to be treated with the right one, however they don’t destroy viruses as they reproduce using your body cells so it is difficult to develop drugs that destroy just the virus without killing the cells
-Use has greatly reduced deaths from bacterial communicable diseases

Question 24

How does bacteria become resistant

Answer 24

-It can mutate so it’s resistant to antibiotics so when it’s treated only the non-resistant strain will be killed
-The individual resistant bacteria will survive and reproduce so the population will increase
-Could cause serous infection like MRSA which became resistant to meticillin and can cause serious infection wounds
-Doctors avoid over-prescribing antibiotics to slow down the rate of development of resistant strains

Question 25

What is aspirin and what is it made from

Answer 25

Made from a chemical found in willow bark it is used as a pain killer and to lower fever

Question 26

What is digitalis used for and made from

Answer 26

Used to treat heart conditions and developed from a chemical found in foxgloves

Question 27

How did Fleming find penicillin

Answer 27

-Clearing petri dishes containing bacteria and one of the dishes had mould and around the mould was freed from bacteria
-Found the mould on the petri dish was producing a substance that killed the bacteria (penicillin)

Question 28

What happens during pre-clinical testing

Answer 28

-Drugs are tested on human cells and tissues in the lab
-You can’t use human cells and tissues to test drugs affecting whole body systems (e.g. a drug for blood pressure must be done on a whole animal as it has an intact circulatory system)

Question 29

What happens in stage 2 of drug testing

Answer 29

-It is tested on live animals to test for efficacy, toxicity and the best dosage
-The law in Britain says any new drug must be tested on two different live mammals and some think it’s cruel to test on animals but other believe it is the safest way to ensure a drug isn’t safe before giving it to humans

Question 30

What happens in stage 3 of drug testing

Answer 30

-If the drug passes the test on animals it’s tested on human volunteers in a clinical trial
-First it is tested on healthy volunteers to ensure no harmful side effects when the body is working normally and at the start a low dose of the drug is given and it gradually increases
-If the results on healthy volunteers are good it can be tested on people suffering from the illness and the optimum dose is found
-To test how well it works placebos are used to see if the drug makes any actual difference
-Clinical trials are blind so neither the doctor nor patients know who was given placebos until the results are gathered so the doctors aren’t subconsciously influenced by their knowledge when monitoring patients and analysing results
-Results aren’t published till they’ve been peer reviewed

Question 31

What is efficacy

Answer 31

Whether the drug works and produces the effect you’re looking for

Question 32

Why do plants need mineral ions

Answer 32

-Nitrates are needed to make proteins for growth
-Magnesium ions are needed for chlorophyll which is needed for photosynthesis plants without enough magnesium suffer from chlorosis and have yellow leaves

Question 33

Common signs in a plant for disease

Answer 33

-Stunted growth
-Spots
-Patches of decay
-Abnormal growth
-Malformed stems or leaves
-Discolouration

Question 34

How can plant diseases be identified by

Answer 34

-Looking up signs in a gardening manual or website
-Taking the plant to a laboratory where scientists can identify the pathogen
-Using testing kits that identify the pathogen using monoclonal antibodies

Question 35

How can plants get diseases

Answer 35

-Viruses, bacteria and fungal pathogens can infect
-They can also be infested and damaged by insects. (E.g. aphids are an insect that can cause huge damage)

Question 36

What physical defences do plants have against disease

Answer 36

-Most plant leaves and stems have a waxy cuticle, which provides a barrier to stop pathogens entering
-Plant cells surrounded by cell walls which forms a barrier against pathogens that make it past the waxy cuticle
-Plants have layers of dead cells around their stems (e.g. bark) which act as barrier to stop pathogens entering

Question 37

What chemical defences do plants have against disease

Answer 37

-Some can produce antibacterial chemicals which kill e.g. the mint plant and witch hazel
-Other plants produce poisons which can deter herbivores (e.g tobacco plants, foxgloves and deadly nightshade)

Question 38

What mechanical defences do plants have against disease

Answer 38

-Some have adapted to have thorns and hairs. Stops animals from touching and eating them
-Other plants have leaves that droop or curl when something touches them. This means that they can prevent being eaten, knocking insects off themselves and moving away from things
-Some plants can cleverly mimic other organisms (species in the ‘ice plant family’ in southern africa look like stones and pebbles so things so don’t eat

Question 39

What produces monoclonal antibodies

Answer 39

-Lots of clones of a single white blood cell
-This means all the antibodies are identical and will only target one specific protein antigen

Question 40

What is a hybridoma and why do they have to be produce

Answer 40

-Lymphocytes that make antibodies don’t divide easily.
-Tumour cells don’t produce antibodies but divide lots
-A mouse B-lymphocyte and tumour cell is fused which can be cloned to get lots of identical cells which produce the same antibodies

Question 41

How are monoclonal antibodies produced

Answer 41

-Mouse is injected with antigen and b-lymphocytes are taken from the mouse
-Fast-dividing tumour cells are taken from a lab and fused with B-lymphocyte
-Mouse b-lymphocyte and b-lymphocyte fused with tumour cell are fused to make a hybridoma
-Which divides quickly to produce lots of clones that produce the monoclonal antibodies

Question 42

How do pregnancy tests work if the person is pregnant

Answer 42

-The part the person urinates on had some antibodies that HGC will bind to (they can move and are stuck to blue beads)
-On the test strip there is the same antibodies however these are stuck down to the test strip
-When a pregnant person urinates on the stick the HGC hormone will bind to the antibodies with the blue beads an the urine will move up the stick carrying the hormone and beads
-The beads and hormone bind to the test strip antibodies so the blue beads get stuck on the strip, turning it blue

Question 43

How do pregnancy tests work if the person isn’t pregnant

Answer 43

When you urinate on the stick there’s nothing to stick the beat beads onto the test strip, so it doesn’t go blue

Question 44

How can monoclonal antibodies treat cancer

Answer 44

-Cancer cells have antigens on their cell membrane called tumour markers
-In a lab you can make monoclonal antibodies that bind to these tumour markers
-An anti-cancer drug can be attached to these monoclonal antibodies. This might be a radioactive substance, a toxic drug or chemical which stops cancer cells growing and dividing
-Given to patient through a drip
-Antibodies target specific cells and only bind to tumour markers killing the cancer cells but not any normal body cells

Question 45

How are monoclonal antibodies used to measure chemical levels

Answer 45

Can bind to hormones/other chemical in the blood to measure their levels

Question 46

How can monoclonal antibodies be used to find pathogens

Answer 46

They can test blood samples in laboratories for certain pathogens

Question 47

How are monoclonal antibodies used to locate specific molecules on a cell or in a tissue

Answer 47

-First, monoclonal antibodies are made that will bind to the specific molecules you’re looking for
-The antibodies are then bound to a fluorescent dye
-If the molecules are present in the sample you’re analysing, the monoclonal antibodies will attach to them, and they can be detected using the dye

Question 48

What are the advantages of monoclonal

Answer 48

-Cancer treatment that doesn’t affect normal body cells as only target specific cells
-Side effects of an antibody based drug are lower than for standard chemotherapy or radiotherapy

Question 49

What are the disadvantages of monoclonal antibodies

Answer 49

-Cause more side effects than originally (e.g. they can cause fever, vomiting and low blood pressure.
-When they were first developed scientists thought that because they targeted a very specific cell or molecule, they wouldn’t create a lot of side effects