Infection and response Flashcards
What are pathogens?
Microorganism that cause disease
what are the types of pathogen?
- virus
- bacteria
- protist
- fungi
how can diseases be spread?
- direct contact eg. athlete’s foot
- water eg. cholera
- air eg. influenza
how do pathogens make you ill?
bacteria - produce toxins=damage cells
viruses - enter a cell=use cell’s nucleus to replicate themselves=replicate quickly=lots of them=cell bursts=new viruses released=cell damage=ill
protists - most are parasites+transferred by a a vector
fungi= hyphae (thread-like structure)=grow+penetrate surface of skin/plants=disease & can also produce spores=spread to others
viral diseases
Measles
- symptoms of fever and a red skin rash
- most young children are vaccinated against measles
- spread by inhalation of droplets from sneezes and coughs
HIV
- causes a flu-like illness
- controlled with antiretroviral drugs= x virus attacks the body’s immune cells.
- late stage HIV infection aka AIDS=body’s immune system becomes so badly damaged it can no longer deal with other infections or cancers
- spread by sexual contact or exchange of body fluids eg. blood, when drug users share needles
Tobacco mosaic virus (TMV) - plant pathogen affecting many species of plants including tomatoes
- gives a distinctive ‘mosaic’
pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis
bacterial disease
Salmonella
- spread by bacteria ingested in food, or on food prepared in unhygienic conditions
- UK=poultry are vaccinated against Salmonella to control the spread
- fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete
Gonorrhoea
- a sexually transmitted disease (STD)
- symptoms=a thick yellow or green discharge from the vagina or penis and pain on urinating
- easily treated with the
antibiotic penicillin until many resistant strains appeared
- spread by sexual contact=controlled by treatment with antibiotics or the use of a barrier method of contraception eg. condoms
fungal disease
Rose black spot
- purple or black spots develop
on leaves=turn yellow and drop early
- affects the growth of
the plant as photosynthesis is reduced
- spread in the environment
by water or wind
- treated with fungicides
and/or removing and destroying the affected leaves
protist disease
Malaria
- malarial protist has a life cycle that includes the mosquito
- causes recurrent episodes of fever and can be fatal
- spread is controlled by preventing the mosquitos from breeding + by using mosquito nets to avoid being bitten
how can we reduce/prevent the spread of disease?
- being hygienic
- destroying vectors
- isolating infected individuals
- vaccination
what are our non-specific defence systems?
- skin
- mucus in nose and trachea
- HCl in stomach
- tears=antiseptic
how do wbc destroy pathogens?
they detect the pathogens by the antigens on its surface then they either:
* phagocytosis - engulfing pathogens + digesting them
* antibody production - specific to pathogen & antibody stored in memory B cells & if person is infected again wbc quickly produce antibodies to kill it
* antitoxin production - specific to bacteria’s toxins
how does a vaccine work?
injecting a dead or inactive version of a virus = wbc recognise antigen+produce antibodies
- same pathogen re-enters the body=wbc quickly produce correct antibodies=preventing infection
pros and cons of vaccines
pros
- epidemics can be prevented if most people in a population are vaccinated
- control spread of communicable disease eg. polio very common before, now x happen
cons
- don’t always work=don’t always give immunity
- bad reaction to a vaccine eg. swelling, fever, seizures=rare
what’s the difference between antibiotics and painkillers?
- painkillers eg. aspirin - relieve pain+reduce symptoms
- antiobiotics eg. penicillin - kill bacteria
how can bacteria become resistant?
- bacteria mutate
- mutation= become resistant to antibiotic
- when you treat it only non-resistant killed
- resistant bacteria survive+reproduce
- more of resistant strain=cause infection x be treated eg. MRSA
stop this from happening
- doctors should avoid over-prescribing antibiotics
- finish whole course of antiobiotic
what commonly used drugs come from plants/microorganism?
- heart drug digitalis originates from foxgloves
- painkiller aspirin originates from willow
- penicillin was discovered by Alexander Fleming from the Penicillium mould
how are most new drugs made?
Most new drugs are synthesised by chemists in the pharmaceutical
industry. However, the starting point may still be a chemical extracted
from a plant
how are drugs developed?
Preclinical testing
- 1st done in a laboratory using cells, tissues
- 2nd live animals=test efficacy+toxicity+best dosage
people think it’s cruel
Clinical trials
- use healthy volunteers and patients:
* Very low doses of the drug are given at the start of the clinical trial
* If the drug is found to be safe, dose is slightly increased until optimum dose for the drug is found
- tested on volunteers with disease if it’s safe
- volunteers with disease are randomly allocated to 2 groups
- one is given the drug and the other a placebo
- accurate dosage found
- often double-blind trials=doctors aren’t influenced by their knowledge
- results of trial are peer reviewed before being published= stops false claims
how are monoclonal antibodies made?
- mouse is injected with an antigen
- B-lymphocytes are combined with a tumour cell=a hybridoma cell
- hybridoma cell can both divide and make the antibody
- hybridoma cells are cloned to produce many identical cells that all produce the same antibody
- large amount of the antibody can be collected and purified.
how are monoclonal antibodies used in pregnancy tests?
- HCG is found in urine of pregnant urine
- where urine goes=antibodies which bind to HCG+blue beads attached to it
- test strip has more antibodies stuck onto it
if you’re pregnant: - hormone binds to antibodies on the blue beads
- urine moves up the stick, carrying HCG and beads
- beads and HCG bind to antibodies on the strip=blue beads get stuck=test strip turn blue
if you’re not pregnant: - urine moves up, carrying blue beads
- nothing sticks to test strip= x turn blue
how are monoclonal antibodies used?
- for diagnosis eg. pregnancy tests
- in laboratories to measure the levels of hormones and other
chemicals in blood, or to detect pathogens - in research to locate or identify specific molecules in a cell or tissue by binding to them with a fluorescent dye
- to treat some diseases: for cancer, the monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical=binds to tumour markers (tumour’s antigens) which stops cells growing and dividing. It delivers the substance to the cancer cells without harming other cells in the body
pros and cons of monoclonal antibodies
pros
- cancer treatment=only target specific cells
- lower side effects compared to chemo/radiotherapy
cons
- cause more side effects than expected eg. fever, vomiting, low blood pressure
- not widely used
how can plants diseases be detected?
- stunted growth
- spots on leaves
- areas of decay (rot)
- growths
- malformed stems or leaves
- discolouration
- the presence of pests
how can the diseases be identified?
- reference to a gardening manual or website
- taking infected plants to a laboratory to identify the pathogen
- using testing kits that contain monoclonal antibodies
what do plants need to prevent disease?
- nitrates=make proteins=growth
lack of nitrates=stunted growth - Mg ions=make chlorophyll=photosynthesis
lack of Mg=chlorosis+yellow leaves
what type of defences do plants have?
Physical
* Cellulose cell walls=barrier against pathogens that pass waxy cuticle
* Tough waxy cuticle=barrier=x pathogens entering
* Layers of dead cells around stems (bark on trees) which fall off= x pathogens entering
Chemical
* Antibacterial chemicals eg. mint+witch hazel= kill bacteria
* Poisons to deter herbivores eg. tobacco plants+foxgloves+deadly nightshade
Mechanical (behaviour)
* Thorns and hairs=deter animals
* Leaves which droop or curl when touched=prevent being eating eg. knocking insects off or moving away
* Mimicry to trick animals eg. passion flowers=bright yellow spots=look like butterfly eggs=butterflies x lay eggs
ice plant family=look like stones=other animals x eat them
Dose vs dosage
Dose
- a measured portion or a quantity of a medicine that must be taken at a time
Dosage
- duration or frequency at which the medicine must be taken
