topic 3 - infection and response Flashcards
what are communicable diseases?
- a disease which can be spread from one person to another
- they are infectious and are spread by pathogens
what are pathogens?
microorganisms that cause infectious disease
what can pathogens be?
- viruses
- bacteria
- protists
- fungi
how do bacteria make us ill?
- once inside the human body, bacteria reproduce very rapidly
- bacteria can then release harmful chemicals called toxins
- toxins damage tissues and make us feel ill
how are viruses different from bacteria?
- viruses cannot reproduce by themselves
- they can only reproduce inside a host cell
how do viruses make us feel ill?
- first, the virus invades the host cell
- the virus now reproduces inside the host cell
- this is very damaging to the cell. When the virus leaves the cell, it can cause the cell to burst open and die
how do pathogens spread?
- some pathogens are spread in the air
e.g. in water droplets (influenza) - other pathogens can be spread directly in water (e.g. cholera)
- some pathogens are spread by direct contact between individuals (eg HIV)
how can we reduce the spread of pathogens?
- washing your hands before eating can prevent the spread of pathogens
- providing people with clean drinking water can also reduce the spread of pathogens
- using a condom during sexual intercourse reduces the spread of HIV
- in the case of some highly infectious diseases such as Ebola, patients may be isolated - this prevents the pathogen from spreading to other people
- vaccination
what are the symptoms of measles?
- fever
- after around 3 days the patient develops a red skin rash
how is the measles virus spread?
- the measles virus is spread in droplets when an infected person coughs or sneezes
- the virus then passes onto a different person when those droplets are inhaled
- in some cases, complications can develop. These can cause damage to the breathing system and the brain
how is the measles virus treated?
most children are vaccinated against measles when they are very young
what are the symptoms of HIV?
- flu-like illness
- unless successfully controlled with antiretroviral drugs, the virus attacks the body’s immune cells
what is late-stage HIV infection or AIDS?
- Late-stage HIV infection, or AIDS, occurs when the body’s immune system becomes so badly damaged it can no longer deal with other infections or cancers
how is HIV spread?
- HIV is spread by sexual contact or the exchange of body fluids such as blood which occurs when drug users share needles
whats is TMV?
- tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes
what are the symptoms of TMV?
- it gives a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis
how is salmonella spread?
- salmonella food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions
how is salmonella treated?
- In the UK, poultry are vaccinated against Salmonella to control the spread
what are the symptoms of salmonella?
- fever
- abdominal cramps
- vomiting
- diarrhoea
-> these are all caused by the bacteria and the toxins they secrete
what is gonorrhoea?
a sexually transmitted disease (STD)
what are the symptoms of gonorrhoea?
- a thick yellow or green discharge from the vagina or penis
- pain whilst urinating
how was gonorrhoea treated in the past?
- gonorrhoea was easily treated using the antibiotic penicillin
- however antibiotic-resistant strains of bacteria are now common
how do we stop the spread of gonorrhoea?
- using a condom during sexual intercourse stops the bacteria from passing from person to person
- people who have unprotected sex should be tested for gonorrhoea as they can then be treated with antibiotics to kill the bacteria before they pass it on to another person
what type of disease is malaria?
- malaria is a communicable disease
- it is spread by a pathogen
- the malaria pathogen is an example of a protist
what are the symptoms of malaria?
- recurrent episodes of fever which can be fatal
how is malaria caused?
- first, the infected person is bitten by a mosquito.
- the malaria pathogen passes into the mosquito
- the mosquito now bites a different person and passes the malaria pathogen to them
what do scientists call the mosquito involved in the malaria process?
- scientists call the mosquito a vector because it carries the pathogen from one person to another person
how can we stop the spread of malaria?
- we need to stop the vector (the mosquito) from breeding
- mosquitoes breed in still water. To stop mosquitoes from breeding, we need to find areas of still water and drain them
- we can also spray areas of still water with insecticide which kills mosquitoes
- We can also prevent mosquitoes from biting humans
-> e.g. sleeping under a mosquito net. the mosquitoes cannot get through the net so they cannot bite anyone sleeping in the bed. Spraying the mosquito net with insecticide kills any mosquitoes that land on it
what is the role of the non-specific defence system?
to prevent pathogens from entering the human body
what is the function of the skin?
- the skin forms a protective layer covering the body
how does the skin defend against pathogens
- the outer layer of the skin consists of dead cells and is difficult for pathogens to penetrate
- the skin also produces an oily substance called sebum which can kill bacteria
what happens when the skin is damaged?
- this could allow pathogens to enter the body
- to stop this, the skin scabs over
how does the nose defend against pathogens?
- the nose contains hairs and mucus.
-> These can trap pathogens before they enter the breathing system. However, sometimes, the pathogens still pass through down to the lungs
how do the trachea and bronchi defend against pathogens?
- the trachea and bronchi are covered with tiny hairs called cilia
-> cilia are covered in mucus which can trap pathogens - the cilia now waft the mucus upwards towards the throat where it is swallowed into the stomach
how does the stomach defend against pathogens?
- the stomach contains hydrochloric acid
- this kills pathogens before they can make their way further down into the digestive system
what is the role of the immune system?
- the immune system destroys pathogens and any toxins they produce
- the immune system protects us incase the same type of pathogen invades us again in the future
what occurs during phagocytosis?
- white blood cells can ingest and destroy pathogens
- the white blood cell detects chemicals released from the pathogen and moves towards it
- the white blood cell then ingests the pathogens
- now the white blood cell uses enzymes to destroy the pathogens
what are antibodies?
antibodies are protein molecules produced by white blood cells
what is the function of antibodies?
- the antibodies stick to the pathogens
- this triggers the pathogens to be destroyed
- antibodies are extremely specific
- antibodies can remain in the blood for a long time. this means they can protect us in case we ever get infected again with the same pathogen
what is the function of antitoxins?
- antitoxins stick to toxin molecules and prevent them from damaging cells
what are rose black spots caused by?
a fungus
what are the symptoms of rose black spots?
- purple or black spots
- the leaves then often turn yellow and fall off
what does rose black spot cause?
rose black spot causes the rate of photosynthesis to fall and this reduces the rate of growth
how is rose black spot spread?
by water or by wind
how is rose black spot treated?
- spraying the plants with chemicals which kill fungi (fungicides)
- we can also remove the infected leaves and destroy them
how does vaccination work?
- vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body
- the white blood cells are now stimulated to produce antibodies against the dead or inactive pathogen
- at the same time, the white blood cell divides by mitosis to produce a lot of copies of itself
- these copies of the white blood cell can stay in the blood for decades
- if the same pathogen now enters the body, even years later, the white blood cells can produce correct antibodies quickly. This prevents infection
what is the role of vaccination?
- vaccines directly protect us from infection by pathogens
what is herd immunity?
- if a sufficiently high proportion of a population is immune to a disease, the spread of this disease will be limited
- this is because the unvaccinated person cannot catch the disease because no one around them can pass the pathogen on
what is the first antibiotic?
penicillin
what is the role of antibiotics?
antibiotics kill infective bacteria inside the human body, without harming body cells
what is antibiotic resistance?
- antibiotic resistance is when antibiotics are overused
- this means that the bacteria has evolved so that they are no longer killed by the antibiotic
what is the role of painkillers?
- painkillers treat the symptoms of a disease by relieving pain
- however medicine such as painkillers do not kill pathogens
why can’t we use antibiotics to kill viruses?
- viruses live and reproduce inside human cells
- because of this, it is difficult to develop drugs that kill viruses without also damaging the body’s tissues
what plant was used to extract the heart drug digitalis?
foxgloves
what plant was used to extract the painkiller aspirin?
willow trees
how was penicillin discovered?
the scientist Alexander Fleming discovered penicillin in the mould penicillium
what three main factors are tested for when developing new drugs?
- toxicity
- efficacy
- dose
what are the stages for developing new drugs?
- preclinical testing
- clinical testing find the optimal dose - low doses of the drug are given to healthy volunteers
why is preclinical testing not carried out on humans?
the drug could be extremely toxic
what is preclinical testing carried out on?
- cells
- tissues
- live animals
what is the optimal dose?
the best dose to treat the disease with the fewest side-effects
what is a placebo?
a tablet or injection with no active drug in it
why will some patients get better if you give them a placebo?
this is because they think they’re being treated so they believe that they’re going to get better
how does a double-blind trial work?
- the test group receive the active drug
- the placebo group receive a dummy drug which looks exactly like the test drug but has no active ingredient
- neither the patients nor the doctors know which people are receiving the active drug and which are receiving the placebo
- this is to stop bias in case the doctors pay closer attention to people receiving the active drug
what are monoclonal antibodies?
- monoclonal antibodies are produced from a single clone of cells
- the antibodies are specific to an antigen and so are able to target a single chemical or cell in the body
- use tumours to divide rapidly
what are the uses of monoclonal antibodies in the body?
- pregnancy testing
- identifying + locating specific molecules
- locating blood clots
- diagnose/treat some cancers
how are monoclonal antibodies produced?
- inject the virus (antigens) into a mouse
- extract (mouse) lymphocytes that make a specific antibody to the antigen
- stimulate (mouse) lymphocytes to produce antibody
- lymphocytes are combined with a tumour cell to create a hybridoma
- the hybridoma that makes the specific antibody is isolated
- hybridoma cloned to create many cells by dividing rapidly and produces the antibody
what is the role of lymphocytes?
lymphocytes produce antibodies against anything that the body detects as foreign (antigens)
what are myeloma cells?
type of tumour cell
what do pregnancy kits test for?
HCG (a hormone) in urine
how is HCG produced?
- this hormone is produced by the placenta of the developing fetus
how does a pregnancy test strip work to show a positive result?
- the woman urinates on the test strip and the urine flows up to the reaction zone -> here the HCG binds to mobile antibodies, which have a blue dye attached to them
- the urine and antibodies continue through the result zone, where the immobilised antibodies bind to HCG as well
- a blue dye is released when the mobilised antibodies bind to the HCG
- mobilised antibodies which don’t bind to HCG are able to bind to the immobilised antibodies in the control zone
- if pregnant and HCG is detected, a blue line will appear in the result and control window
what are the advantages of using monoclonal antibodies to test for pathogens?
- specific to one particular antigen
- very accurate
- quick results
how can monoclonal antibodies be used for location?
- monoclonal antibodies are attached to fluorescent dyes
- the antibodies then stick to specific molecules within the cell and allow us to see their locations
how do aphids destroy plants?
- aphids are insects that have a sharp mouth to penetrate the phloem vessel to feed off the plant’s sugar-rich phloem sap
- they prevent the plant from using the products of photosynthesis
- they also act as vectors carrying viruses, bacteria and fungal diseases from one plant to another
how can we get rid of aphids?
- chemical pesticides kill aphids
- biological pest control -> release insects like ladybirds which eat aphids
what are possible ways you can spot diseases in plants?
- stunted growth
- spots on leaves
- an area of decay or rotting
- malformed stems or leaves
- discolouration - yellow leaves
- visible aphids infestation of pests
what are treatments for diseases in plants?
- fertilisers
- antifungal treatment
- remove area of plant
- chemical or biological pesticides
what is the effect of a lack of chlorophyll?
- less chlorophyll results in less light energy absorbed for photosynthesis
- less photosynthesis -> less glucose produced
-glucose is used to make proteins - lack of protein results in stunted growth
what two ions are important to plants?
- nitrate ions
- magnesium ions
what is a symptom of nitrate ion deficiency in plants?
stunted growth
why does lacking nitrate ions cause symptoms?
lack of nitrate ions -> less glucose for proteins
less proteins -> stunted growth
what is a symptom of magnesium ion deficiency in plants?
yellow leaves (chlorosis)
what are the magnesium ions used for?
making chlorophyll
what are physical defence responses to resist the invasion of microorganisms?
- cellulose cell walls
- tough waxy cuticles on leaves
- layers of dead cells around stems which fall off
what are chemical plant defence responses?
- anti-bacterial chemicals
- poisons to deter herbivores
what are mechanical plant defence responses?
- thorns and hairs deter animals
- leaves that droop or curl when touched
- mimicry to trick animals
what are the three diseases that the MMR vaccine protects?
- measles
- rubella
- mumps
what does thalidomide treat?
- leprosy
what is one advantage to the population as a whole of children having the second MMR vaccination?
- less chance of epidemic
how does a vaccination prevent infection?
- white blood cells produce antibodies
- antibodies produced rapidly
- these antibodies kill pathogens
why should all tools be disinfected after using them on plants infected with TMV?
- to prevent the virus from spreading
how can scientists use a plant that contains a TMV-resistant gene to produce many plants with the same gene?
- take stem cells from meristem
what testing must be done before a new drug can be used to treat people?
- preclinical trials of the new drug on live animals to test toxicity, dosage, efficacy
- clinical trials, test on healthy volunteers + patients at very low doses so that you can monitor for safety/side effects and only then do trials to find the optimum dosage + test for efficacy
- double-blind trial (placebo which does not contain the new drug)
- random allocation of patients to groups so no one knows who has placebo
- peer review of data to help prevent false claims
how does the immune system defend the body against pathogens?
- bacteria + viruses are pathogens which reproduce rapidly inside the body
- bacteria may produce toxins that make us feel ill
- viruses live and reproduce inside cells causing damage
- white blood cells help to defend against pathogens by:
- engulfing pathogens
- producing antibodies to destroy particular pathogens
- producing antitoxins to counteract toxins
- this leads to immunity from that pathogen
how might an infection which damages the mucus lining around the stomach result in a stomach ulcer developing?
- bacteria are not killed so it damages the mucus lining
- so HCI damages stomach tissue/ causes an ulcer
coeliac disease damages the villi, why might this lead to poor growth?
- damaged villi reduce surface area for absorption
- therefore fewer amino acids + glucose absorbed
- with less glucose, transfer of energy from respiration is reduced
- and fewer amino acids available to build new proteins
how does nicotine cause a person to become addicted?
- alters body chemistry
how does the ‘nicotine vaccine’ help wean a smoker off nicotine?
- if nicotine is taken, antibodies bind to nicotine molecules
- making them too large to get to brain
what are the effects of adding large amounts of methane to the atmosphere?
- absorbs energy radiated by the Earth
- some energy reradiated
- leading to global warming/ enhanced greenhouse effect
why can’t antibiotics be used to cure viral diseases?
- viruses live inside cells
- so viruses are inaccessible to antibiotics
why has there been a large increase in antibiotic-resistant strains of bacteria?
- overuse of antibiotics cause non-resistant strains killed by antibiotics
- so less competition
