Infection and Response Flashcards
What is a communicable disease?
A disease caused by a pathogen which can be passed between animals or plants eg. flu.
What is a pathogen?
A disease-causing microorganism e.g.
bacteria.
How do bacteria cause disease?
Once inside the body, they divide rapidly by binary fission. They kill cells and produce harmful toxins.
How do viruses cause disease?
They invade and reproduce inside living
body cells, leading to cell damage.
Give three ways in which pathogens can be
spread
● By air - flu, tuberculosis and the common cold are spread by droplet infection.
● By water - fungal spores in water spread plant diseases.
● By direct contact - common in plant diseases and sexually transmitted infections.
Give four ways in which the spread of
pathogens can be reduced
● Hygiene - handwashing, disinfectants, tissues.
● Reducing contact with infected individuals - quarantine.
● Removing vectors - use of pesticides and insecticides, removal of habitats.
● Vaccination.
Why is it especially important to prevent the spread of viral diseases?
Scientists have not yet developed cures for many viral diseases.
Uncontrolled spread of disease could lead to a global pandemic.
What is measles?
Measles is a viral disease that can
cause blindness and brain damage. The
main symptoms are a fever and a red skin
rash.
How is measles spread?
By air - through the inhalation of droplets from coughs and sneezes.
What is HIV/AIDS?
HIV is a virus which attacks and damages the
immune system until it can no longer function
properly. AIDS is the condition resulting from a
long-term HIV infection. There is no cure or
vaccine for HIV/AIDS.
How is HIV spread?
Direct sexual contact and the exchange
of bodily fluids eg. blood, breastmilk.
How can the spread of HIV/AIDS be prevented?
● Use of condoms ● Screening of blood for transfusions ● Not sharing needles ● Bottle-feeding by HIV-positive mothers ● Use of antiretroviral drugs to prevent the development of AIDS
What is tobacco mosaic virus?
A plant pathogen which causes leaf discolouration
when cells are damaged. Affected areas cannot
photosynthesise, reducing the crop yield. As there is
no treatment, farmers grow TMV-resistant crop
strains to avoid infection.
How is tobacco mosaic virus spread?
Contact between infected and healthy plants.
Insects may act as vectors which transfer the
virus between different plants.
What is salmonella?
A type of bacteria found in raw meat, poultry
and eggs. If they enter the body via food
poisoning, they can affect natural gut
bacteria.
What are the symptoms of salmonella food
poisoning?
● Fever ● Abdominal cramping ● Vomiting ● Diarrhoea May be fatal in very young or elderly populations due the risk of dehydration.
How can the spread of salmonella be limited?
● Vaccinating animals intended for consumption
● Keep raw meat away from cooked meat
● Disinfect hands and surfaces after contact with
raw meat
● Thoroughly cook meat
What is gonorrhoea?
A sexually transmitted bacterial infection caused by
unprotected sex with an infected individual. Early symptoms
include yellow/green discharge from genitals and painful
urination, although it may be symptomless.
Its spread can be controlled through the use of antibiotics (no
longer penicillin as many strains are resistant) and using
condoms.
What is rose black spot?
fungal disease which causes purple or black
spots to develop on rose leaves. It reduces the
area of the leaf which is available for
photosynthesis and causes leaves to turn yellow
and drop prematurely.
How is the rose black spot fungus spread?
Fungal spores are spread by the wind
and in water
How can the rose black spot fungus be treated?
● Using fungicides
● Destroying infected leaves
What is malaria?
Malaria is a disease caused by protist pathogens.
The disease is carried from host to host by
mosquitoes, and the protists enter the human
bloodstream when they feed. Symptoms include
fever and shaking, and it may also be fatal.
How can the spread of malaria be reduced?
● Using insecticides ● Using insect nets to avoid bites ● Prevent mosquito breeding by removing stagnant water ● Antimalarial drugs
How does the skin prevent pathogens from
entering the body?
● Acts as a physical barrier.
● Scab formation after skin is cut/wounded.
● Antimicrobial secretions which can kill pathogens.
● Healthy skin flora compete with pathogens and
act as an additional barrier.
How does the respiratory system prevent
pathogens from entering the body?
● Nose - has hairs and mucus which trap
pathogens.
● Trachea and bronchi - have mucus that traps
pathogens. Ciliated cells move mucus to the
mouth so it can be swallowed.
How does the stomach prevent pathogens
infecting the body?
● Secretes hydrochloric acid - kills any pathogens
present.
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.
How does antitoxin production protect us
against disease?
Antitoxins bind to toxins released by pathogens and
neutralise them.
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 and prevent illness.
What is herd immunity?
If a sufficiently high proportion of a population are
immune to a disease (especially through
vaccination), the spread of this disease will be
limited.
What are the advantages of vaccinations?
● They have eradicated many deadly diseases eg.
smallpox.
● Many epidemics can be prevented by
vaccinations.
● Herd immunity protects those who cannot have
vaccinations.
What are the disadvantages of vaccinations?
● Not guaranteed to work on every strain/mutation of pathogen
● May be side effects or adverse reactions.
What drugs are used to cure some bacterial
diseases?
Antibiotics - they can kill bacterial pathogens inside
the body
Why can antibiotics not be used to treat viral
diseases?
Antibiotics have no effect on viral pathogens as they
live inside the host’s (human) cells. Therefore, it is
difficult to design drugs that would kill the virus and
not destroy human cells at the same time.
What is antibiotic resistance?
Antibiotic resistance occurs when mutations lead to
individual bacteria being resistant to an antibiotic. These
bacteria are able to survive, reproduce and pass on their
alleles, leading to a greater proportion of antibiotic-resistant
bacteria. This is concerning as some types of bacteria are
becoming resistant to all known antibiotics, so the diseases
that they cause cannot be cured.
How can we prevent antibiotic resistance?
● Avoid overuse and unnecessary use of antibiotics
- eg. antibiotics are often used for viral infections.
● Finish antibiotic courses - to ensure all bacteria is
killed.
What effect do painkillers have on
infectious diseases?
Painkillers can only treat the symptoms e.g. reducing fever but do not
kill pathogens.
What plant is the heart drug digitalis extracted from?
Foxgloves
What painkiller originates from a compound
found in willow bark?
Aspirin
Who discovered penicillin?
Alexander Fleming
What three main factors are tested for when
developing new drugs?
● Toxicity
● Efficacy
● Dose
How is preclinical testing carried out?
In a laboratory - uses cells, tissues and live animals
How is clinical testing carried out?
Uses healthy volunteers and patients. Firstly, the
drug is tested at a low dose on healthy people - then
tested on patients and on a larger scale to find the
optimum dose. Often, one group receive a placebo
(not the test drug) and the other group receive the
actual drug, in order to assess its efficacy.
What is the difference between a single-blind
and a double-blind trial?
In a single-blind trial, only the doctor knows whether
the patient is receiving the drug or the placebo. In a
double-blind trial, neither the patient nor the doctor
knows. Double-blind trials help remove bias on the
part of the doctor.
What is a peer review?
Where the results of drug trials are checked over by
scientists knowledgeable in this field.
What are monoclonal antibodies
● Antibodies that are clones from one
parent cell
● Specific to one type of antigen
Describe how monoclonal antibodies are
produced
- Specific antigen injected into an animal (e.g. mouse).
- B-lymphocytes producing complementary antibodies extracted.
- B-lymphocytes fuse with myeloma cells to form hybridoma
cells - these cells can divide and produce antibody. - Hybridoma cells cultured.
- Monoclonal antibodies 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 do pregnancy kits test for?
hCG in urine
Describe what happens to the test stick if
a woman 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.
Why can monoclonal antibodies be used
to target cancer cells?
● Cancer cells have specific antigens called ‘tumour
markers’ on their membranes.
● mAbs are specific to one type of antigen so can be
targeted to ‘tumour markers’ without damaging other
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 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
(chlorosis).
What are the symptoms of disease in plants?
● Stunted growth (lack of nitrate ions) ● Spotted leaves (eg. rose black spot fungus) ● Decay/rotting ● Growths ● Malformation of stems/leaves ● Discolouration ● Presence of pests
What are three ways in which plant disease
can be identified?
● Reference to a gardening website or manual
● Laboratory testing
● Monoclonal antibody test kits
Give examples of physical defence
responses used by plants
● Cellulose cell walls
● Tough waxy cuticle on leaves
● Outside layer on stems/bark on trees
● Leaf fall
Give examples of mechanical defence
responses used by plants
● Thorns and hairs to deter animals
● Leaves that droop/curl on contact
● Mimicry to trick animals
