B3: Infection and Response Flashcards
What is a communicable disease
A disease caused by a pathogen which can be passed down between animals or plants eg. Flu
What is a pathogen?
A disease-causing microorganism e.g. bacteria
How do bacteria cause disease?
- 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 and examples
- by air - flu, tuberculosis and the common cold are spread by droplet infection
- by water- fungal spores in water spread plant disease
- 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,
- reducing contact with infected individuals: quarantine
- removing vectors: use of pesticides and insecticides, removal of habitats
- vaccination
Why is it important to prevent the spread of viral disease?
- scientists have not yet developed cures for many viral diseases
.Define ‘health’.
State of physical and mental well-being
What is measles? Give the main symptoms
- Measles is a serious viral disease that can cause blindness and brain damage
- fever and a red skin rash
how is measles spread ?
by air: through the inhalation of droplets from coughs and sneezes
What is HIV?
- A virus which attacks and damages the immune system until it can no longer function properly
What is AIDS?
AIDS: condition resulting from a long-term HIV infection
How is HIV spread?
- Direct sexual contact
- the exchange of bodily fluids e.g. blood, breastmilk
Give 5 ways 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
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
Give 4 symptoms of salmonella food poisoning?
- fever
- abdominal cramping
- vomiting
- Diarrhoea
May be fatal in very young or elderly populations due the risk of dehydration
Give four ways 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
Give symptoms of gonorrhoea
- yellow/green discharge from genitals
- painful urination
State 3 long-term effects of gonorrhoea.
- Long-term pelvic pain,
- infertility
- ectopic pregnancies
give three ways the spread of gonorrhoea be
stopped?
- Use condom
- Limit sexual partners
- spread can be controlled through the use of antibiotics
what is rose black spot?
- A 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
Give two ways the rose black spot fungus can be treated?
- using fungicides
- destroying infected leaves
.How can we use Agrobacterium tumefaciens
in plants?
They cause galls –> genetic manipulation
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
Give symptoms of malaria
- fever
- shaking
Give four ways the spread of malaria be reduced
- using insecticides
- using insect nets to avoid bites
- prevent mosquito breeding by removing stagnant water
- antimalarial drugs
Give four ways the skin prevents 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
Give two ways 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
State the three ways in which white blood
cells defend the body.
- Engulf pathogens
- Produce antibodies
- Produce antitoxins
How does antibody production protect us against disease? (3
- 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 to 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 and how does it work
- 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 ( through vaccination)
- the spread of this disease will be limited
Give three advantages of vaccinations
- eradicated many deadly diseases
- epidemics can be prevented
- herd immunity protects those who cannot have vaccinations
Give two disadvantages of vaccinations
- not guaranteed to work as might not protect against multiple strains 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
How do antibiotics work?
- antibiotics kill bacterial pathogens inside the body but not human cells
Why are antibiotics ineffective to treating viral diseases
- have no effect on viral pathogens as they live inside the host human cells
- it is difficult to design drugs that would kill the virus and not destroy human cells at the same time
What is 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
give two ways to prevent antibiotic resistance
- avoid overuse and unnecessary use of antibiotics
- finish antibiotic courses to ensure all bacteria is killed
What effect do painkillers have on infectious diseases?
- painkillers can only treat the symptoms such as mild to moderate pain but do not kill pathogens
Which plant did the heart drug digitalis
originated from?
Foxgloves
What painkiller originates from a compound found in willow bark?
Aspirin
What type of antibiotic was discovered by Alexander Fleming from a type of mould?
Penicillin
What are the 4 qualities of a good medicine?
- efficacy
- safety
- stable
- able to be taken in and removed easily
New drugs are tested extensively for three
factors. Name the three factors.
Toxicity, efficacy, dose
How is preclinical testing carried out?
in a lab - using cells, tissues and live animals
Describe how clinical testing is carried out (4)
- uses healthy volunteers and patients
- 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
- one group receives a placebo and the other group receive the actual drug to test efficacy
What is the difference between a single-blind and a double blind trial?
single-blind trial: only the doctor knows whether the patient is receiving the drug or the placebo
double blind trials: neither the patient nor the doctor knows ; helps remove bias on the part of the doctor
Define placebo
A medicine that does not contain the active
drug being tested
define ‘ peer review’
- where the results of drug trials are checked over by scientists knowledgeable in this field
what are monoclonal antibodies (mAbs)?
- 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
- B-lymphocytes producing complementary antibodies extracted
- B-lymphocytes fuse with myeloma ( tumour) cells to form hybridoma cells - these cells can divide and produce antibody
- Hybridoma cells are cultured
- Monoclonal antibodies collected and purifed
Outline the 5 uses of monoclonal antibodies
- used in pregnancy tests
- Disease diagnosis
- Monitoring chemical levels in blood
- location of cancer cells and blood clots
- treatment of Cancer
What are myeloma cells?
- type of tumour cells
What do pregnancy kits test for?
hCG in urine
What does a pregnancy test consist of?
- A stick containing monoclonal antibodies (mABs) specific to hCG
- mABs attached to a blue bead ( free to move)
- mABs fixed to the test stick
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
if not pregnant:
no hCG so a blue line is not formed
Give 3 advantages of using monoclonal antibodies to test for pathogens
- specific to one particular antigen
- very accurate
- quick results
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
Describe how monoclonal antibodies can be used to diagnose cancer
- mAbs attached 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
Give three reasons why cancer treatments that use monoclonal antibodies favoured over traditional treatments
- radiotherapy and chemotherapy target rapidly dividing cells - no way to differentiate from healthy cells
- healthy cells (e.g. hair follicle ells ) are damaged as a consequence , producing unpleasant side effects
- mAbs only target cancer cells, reducing damagee to normal cells
How can monoclonal antibodies be used to locate blood clots?
- mAbs attached 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
What is a disadvantage to the use of monoclonal antibodies on treatment?
More side effects than expected (skin rash)
How do aphids damage
plants?
- Feed on phloem sap, so plant loses glucose
which can be converted to proteins for growth.
This means less proteins is produced and the
plants suffer from stunted growth - Vectors of pathogens
Give two ways we can 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 ( by joining with glucose) into proteins for growth
- the growth of the plant will be stunted if there is inadequate supply
Why do plants need a good supply of magnesium ions?
- ions are required to synthesise chlorophyll which absorbs light energy during photosynthesis
- the leaves as a result of a lack of supply cannot photosynthesise properly and they turn yellow ( chlorosis)
Give 6 symptoms of disease in plants ?
- stunted growth
- spotted leaves
- decay/rotting
- malformation of stems/leaves
- discolouration
- presence of pests
Give three ways in which plant disease can be identified?
- reference to a gardening website or manual
- laboratory testing
- monoclonal antibody test kits
Give 4 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 two examples of chemical defence responses used by plants
- antibacterial chemicals
- poisons
Give three examples of mechanical defence responses used by plants
- thorns and hairs to deter animals
- leaves that droop/ curl on contact
- mimicry to trick animals
