Topic 3-Infection and Response Flashcards
What are pathogens?
They are microorganisms that cause infectious disease. This includes, bacteria, protists and fungi
What is a communicable disease?
A disease caused by a pathogen which can be passed between animals or plants
How do viruses cause disease?
They move into cells and use the biochemistry of it to make many copies of itself
This leads to the cell bursting and releasing all of the copies into the bloodstream
The damage and the destruction of the cells makes the individual feel ill
How do bacteria cause disease?
They multiply very quickly through dividing by binary fission.
They produce toxins that can damage cells
What are fungi?
They can either be single celled or have a body made of hyphae
They can produce spores which can be spread to other organisms
How can pathogens be spread?
Direct contact- touching contaminated surfaces
By water-drinking or coming into contact with dirty water
By air-pathogens can be carried in the air and then breathed in
How can the damage that is caused by diseases be reduced?
- Improving hygiene (hand washing, using disinfectants, using tissues)
- Reducing contact with infected individuals
- Removing vectors (by using pesticides)
- Vaccination
Why is it especially important to prevent the spread of viral diseases?
Scientists have not yet developed cures for many viral diseases
What is measles and what are its symptoms?
Its a virus
Fever and red skin rash
Can lead to pneumonia, encephalitis (brain infection) and blindness
How is measles spread and prevented?
It is spread by droplet infection
It is prevented by vaccination at a young age
What is HIV and what are its symptoms?
Initially flu-like symptoms, then the virus attacks the immune system and leads to AIDS (body becomes susceptible to many different diseases)
How is HIV spread and prevented?
It is spread by sexual contact or exchange of bodily fluids such as blood
The spread is prevented by using condoms, not sharing needles, screening blood
Development of AIDS-use of antiretroviral drugs (stop replication of virus)
What is the tobacco mosaic virus and what are its symptoms?
A plant pathogen affecting many species of plants including tomatoes
Discolouration of leaves, the affected part of the leaf cannot photosynthesise resulting in the reduction of the yield
How is tobacco mosaic virus spread and prevented?
Contact between diseased plants and healthy plants, insects act as vectors
Good field hygiene and pest control
Growing TMV-resistant strains
What is salmonella food poisoning and what are its symptoms?
Bacteria that live in the gut of different animals, which we ingest when we eat the meat
Fever, stomach cramps, vomiting, diarrhoea
How is salmonella spread and prevented?
These bacteria can be found in raw meat and eggs, unhygienic condition
Poultry are vaccinated against Salmonella, keeping raw meat away from cooked food, avoid washing it, wash hands and surfaces when handling it, cook food thoroughly
What is gonorrhoea and what are its symptoms?
It is a bacteria
Thick yellow or green discharge from the vagina or penis, pain when urinating
How is gonorrhoea spread and prevented?
It is a sexually transmitted disease spread through unprotected sexual contact
By using contraception such as condoms and antibiotics (used to be treated with penicillin but many resistant strains are developing)
What is rose black spot and what are its symptoms?
Purple or black spots on leaves of rose plants, reduces the area of the leaf available for photosynthesis, leaves turn yellow and drop early
How is rose black spot spread and prevented?
The spores of the fungus are spread in water (rain) or by wind
By using fungicides or stripping the plant of affected leaves (have to be burnt)
What is malaria and what are its symptoms?
Caused by protist pathogens that enter red blood cells and damage them
Fevers and shaking (when the protists burst out of blood cells)
How is malaria spread and prevented?
The vector is the female Anopheles mosquito, in which the protists reproduce sexually. When the mosquito punctures the skin to feed on blood, the protists enter the human bloodstream via their saliva
Using insecticide coated insect nets while sleeping, removing stagnant water to prevent the vectors from breeding, travellers taking antimalarial drugs to kill parasites that enter the blood
How does the skin work to prevent pathogens from entering the body?
- Acts as a physical barrier
- Produces antimicrobial secretions to kill pathogens
- Good microorganisms known as skin flora complete with the bad microorganisms for space and nutrients
How does the nose work to prevent pathogens from entering the body?
Has hairs and mucus (sticky substance) which prevent particles from entering your lungs
How does the trachea and bronchi work to prevent pathogens from entering the body?
- Secrete mucus in order to trap pathogens
- Cilia (hair-like structure on cells) beat to waft mucus upwards so it can be swallowed
How does the stomach work to prevent pathogens from entering the body?
Produces hydrochloric acid that kills any pathogens in your mucus, or food and drink
How does phagocytosis protect us against disease?
White blood cells (phagocytes) ingest and destroy pathogens so they cannot infect more cells
How does antibody production protect us against disease?
White blood cells produce antibodies which are complementary to a specific antigen on a pathogen
The binding of antibodies to antigens causes pathogens to clump together, making them easier to destroy
In the case of a second infection, the correct antibodies can be produced rapidly, preventing the person getting the same disease again (immune)
How does antitoxin production protect us against disease?
Antitoxins bind to toxins released by pathogens and neutralise them
What is herd immunity?
Immunising a large proportion of the population meaning the spread of the pathogen will be reduced as there are less people to catch the disease from
What is a vaccination?
Contains a dead or inactivated form of the pathogen which stimulates white blood cells to produce complementary antibodies to the pathogen. In the case of a second infection, memory cells can rapidly produce the correct antibodies
What are the advantages of vaccination?
They have eradicated many disease so far (eg smallpox) and reduced the occurrence of many (rubella)
Epidemics can be prevented through herd immunity
What are the disadvantageds of vaccination?
They are not always effective in providing immunity
Bad reactions (such as fevers) can occur in response to vaccines
What are monoclonal antibodoes?
They are identical antibodies that have been produced from the same immune cell.
As a result of their ability to bind to only one protein antigen, they can be used to target chemicals and cells in the body
Describe how monoclonal antibodies are produced
- Scientists obtain mice lymphocytes (a type of white blood cell that make antibodies but cannot divide), which have been stimulated to produce a specific antibody
- They are combined with tumour cells (do not make antibodies but divide rapidly), to form a cell called a hybridoma
- The hybridoma can divide to produce clones of itself, which all produce the same antibody
- Antibodies are collected and purified
Outline the uses of monoclonal antibodies
Detection of pathogens
Location of cancer cells and blood clots
Treatment of cancer
Used in pregnancy test kits
What are myeloma cells?
Type of tumour cell
What do pregnancy kits test for?
hCG in urine
What does a pregnancy test consist of?
The first section has mobile antibodies complementary to the hCG hormone-these antibodies are also attached to blue beads
The second section has stationary antibodies complementary to the hCG hormone which are stuck down to the stick
Describe what happens to the test stick if a person is pregnant
- hCG in urine binds to mAbs attached to a blue bead
- mAbs with hCG diffuse up dipstick
- mAbs fixed to the stick bind to hCG
- Blue line forms
What is the advantage of using monoclonal antibodies to test for pathogens?
- They only bind to specific cells, meaning healthy cells are not affected
- They can be engineered to treat many different conditions
- We are now able to produce mouse-hybrid cells to reduce the chance of triggering an immune response
Describe what happens to the test stick if the pathogen is not present
No hCG in urine so a blue line is not formed
What are the disadvantages of using monoclonal antibodies?
It is difficult to attach monoclonal antibodies to drugs
They are expensive to develop
As they were produced from mice lymphocytes, they often triggered an immune response when used in humans
Why can monoclonal antibodies be used to target cancer cells?
-Cancer cells have specific antigens called ‘tumour marker’ on their membranes
mAbs are specific to one type of antigen so they can be targeted to tumour markers without damaging other cells
Describe how monoclonal antibodies can be used to diagnose cancer
mAbs tagged to a radioactive substance
mAbs injected into the patient’s bloodstream
mAbs bind to tumour markers on cancer cells
Emitted radiation is detected using a specialised scanner enabling doctors to determine the location of cancer cells
How can monoclonal antibodies be used to target drugs to cancer cells?
mAbs attached to an anti-cancer drug
mAbs injected into the patient’s bloodstream
mAbs bind to tumour markers on cancer cells
Anti-cancer drug destroys cancer cells
Why are cancer treatments that use monoclonal antibodies favoured over traditional treatments?
Radiotherapy and chemotherapy target rapidly dividing cells. As a consequence, healthy cells are damaged, producing unpleasant side effects
mAbs only target cancer cells, reducing damage to normal cells
How can monoclonal antibodies be used to locate blood clots?
mAbs tagged to a radioactive substance
mAbs target and bind to specific proteins in blood clots
Radiation emitted by mAbs is detected, enabling the location of blood clots to be identified
How can monoclonal antibodies be used in laboraties to measure and conduct?
Can be used to monitor levels of hormones or chemicals in the blood
mAbs are modified so that they will bind to the molecule you are looking for
mAbs are also bound to a florescent dye
If the molecules are in the sample then the antibodies bind to it, and the dye can be observed
What are some common signs of plant disease?
Stunted growth Spots on leaves Areas of decay Abnormal growths Malformed stems or leaves Discolouration Pests on leaved
How do aphids cause damage to plants?
They use their sharp mouthparts to extract sap from the plant phloem, weakening the plant
They are also vectors who can transfer pathogens from diseased plants to healthy plants
How can we reduce the number of aphids?
Chemical pesticides
Biological pest control - using ladybirds
Why do plants need a good supply of nitrate ions?
Nitrate ions are required to convert sugars into proteins which are required for the plant to grow.
As a result, the growth of the plant will be stunted if there is not an adequate supply of nitrates
Why do plants need a good supply of magnesium ions?
Magnesium ions are required to synthesise chlorophyll, which absorbs light energy during photosynthesis.
As a result, the leaves cannot photosynthesise properly and they turn yellow
What are three ways in which plant disease can be identified?
Reference to a gardening website or manual
Laboratory testing
Monoclonal antibody test kits to identify the pathogen
Give examples of physical defence responses used by plants
- Cellulose cell walls
- Tough waxy cuticle stops entry into leaves
- Plants have layers of dead cells around stems (eg bark) which stop pathogens from entering. The dead cells fall off with the pathogens
- Leaf fall
Give examples of chemical defence responses used by plants
- Antibacterial chemicals which kill bacteria
- Poisons deter herbivores
Give examples of mechanical defence responses used by plants
Thorns and hairs to deter animals
Some leaves can droop of curl when touched which allowed them to move away and move insects off their leaves
Mimicry to trick animals (Some plants droop to look unhealthy so that animals avoid them)
