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AQA Biology > Infection and response > Flashcards

Infection and response Flashcards

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1
Q

What are pathogens?

A

Microorganism that cause disease

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2
Q

what are the types of pathogen?

A
  • virus
  • bacteria
  • protist
  • fungi
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3
Q

how can diseases be spread?

A
  • direct contact eg. athlete’s foot
  • water eg. cholera
  • air eg. influenza
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4
Q

how do pathogens make you ill?

A

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

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5
Q

viral diseases

A

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

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6
Q

bacterial disease

A

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

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7
Q

fungal disease

A

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

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8
Q

protist disease

A

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

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9
Q

how can we reduce/prevent the spread of disease?

A
  • being hygienic
  • destroying vectors
  • isolating infected individuals
  • vaccination
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10
Q

what are our non-specific defence systems?

A
  • skin
  • mucus in nose and trachea
  • HCl in stomach
  • tears=antiseptic
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11
Q

how do wbc destroy pathogens?

A

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

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12
Q

how does a vaccine work?

A

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

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13
Q

pros and cons of vaccines

A

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

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14
Q

what’s the difference between antibiotics and painkillers?

A
  • painkillers eg. aspirin - relieve pain+reduce symptoms
  • antiobiotics eg. penicillin - kill bacteria
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15
Q

how can bacteria become resistant?

A
  • 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

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16
Q

what commonly used drugs come from plants/microorganism?

A
  • heart drug digitalis originates from foxgloves
  • painkiller aspirin originates from willow
  • penicillin was discovered by Alexander Fleming from the Penicillium mould
17
Q

how are most new drugs made?

A

Most new drugs are synthesised by chemists in the pharmaceutical
industry. However, the starting point may still be a chemical extracted
from a plant

18
Q

how are drugs developed?

A

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

19
Q

how are monoclonal antibodies made?

A
  • 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.
20
Q

how are monoclonal antibodies used in pregnancy tests?

A
  • 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
21
Q

how are monoclonal antibodies used?

A
  • 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
22
Q

pros and cons of monoclonal antibodies

A

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

23
Q

how can plants diseases be detected?

A
  • stunted growth
  • spots on leaves
  • areas of decay (rot)
  • growths
  • malformed stems or leaves
  • discolouration
  • the presence of pests
24
Q

how can the diseases be identified?

A
  • reference to a gardening manual or website
  • taking infected plants to a laboratory to identify the pathogen
  • using testing kits that contain monoclonal antibodies
25
Q

what do plants need to prevent disease?

A
  • nitrates=make proteins=growth
    lack of nitrates=stunted growth
  • Mg ions=make chlorophyll=photosynthesis
    lack of Mg=chlorosis+yellow leaves
26
Q

what type of defences do plants have?

A

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

27
Q

Dose vs dosage

A

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

AQA Biology (7 decks)

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