B3 Flashcards
What is a pathogen?
A disease-causing microorganism
How do bacteria causes diseases?
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?
Air, water, direct contact
Give four ways in which the spread of pathogens can be reduced?
Hygiene
Reducing contact with infected
Removing vectors
Vaccination
Why is it especially important to prevent the spread of viral diseases?
Scientists have not yet developed cures for many viral diseases
What is measles?
Measles is a serious viral disease that can cause blindness and brain damage. The main symptoms are fever and a red skin rash
How’s is measles spread?
Air
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 long-term HIV infections. There is no cure or vaccine
How is HIV spread?
Direct contact
How can the spread of HIV be prevented?
Use of condoms
Screening of blood transfusions
Not sharing needles
Bottle-feeding by HIV-positive mothers
Use of antiretroviral drugs to prevent the development of AIDs
What is the 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
What is salmonella?
A type of bacteria found in raw meat, poultry and eggs. If they enter the body they can affect natural gut bacteria
What are the symptoms of salmonella food poisoning?
Fever
Abdominal cramping
Vomiting
Diarrhoea
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
Cook meat thoroughly
What is gonorrhoea?
An STD bacteria infection caused by unprotected sex
What are the symptoms of gonorrhoea?
Yellow/green discharge from genitals and painful urination (can be symptomless)
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
How can rose black spot fungus be treated?
Using fungicides
Destroying infected leaves
What is malaria?
A disease caused by protist pathogens.
It is carries host to host by mosquitoes and the portists enter the human blood stream when they feed
What are the symptoms of malaria?
Fever and shaking
How can the spread of malaria be reduced?
Using insecticides
Using insect nets to avoid bites
Prevent mosquito breeding by romping stagnant water
Antimalarial drugs
How does the skin prevent pathogens from entering the body?
Acts as a physical barrier
Scab formation after skin is broken
Antimicrobial secretion which kill pathogens
Healthy skin flora compete with pathogens
How does the respiratory system prevent pathogens from entering the body?
Nose - has hairs and muscles that trap pathogens
Trachea and bronchi - have mucus that traps pathogens
How does the stomach prevent pathogens infecting the body?
Secretes hydrochloric acid
How does phagocytosis protect us against disease?
White blood cells 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
What is herd immunity?
If a sufficiently high proportion of a population are immune to a disease the spread of this disease will be limited
What are the advantages of vaccinations?
They have eradicated many deadly diseases
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 - might not protect against multiple strains of a pathogen
May be side effects or adverse reactions
What drugs are used to cure some bacterial diseases?
Antibiotics - they can kill bascerial pathogens inside the body
How do antibiotics work?
Antibiotics kill bacteria pathogens inside the body, but do not kill human cells. Whilst some antibiotic kill a wide range of bacteria it is important that the right antibiotic is used for specific bacteria
Why can antibiotics not be used to treat viral diseases?
They live inside the hosts 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
Finish antibiotic courses
What effect do painkillers have on infectious diseases?
Painkillers can only treat the symptoms but do not kill pathogens
What plant is the heart frug digitalis extracted from?
Foxgloves
What painkiller originates from a compound found in willow bark?
Aspirin
What antibiotic was discovered by Alexander Fleming from a type of mould?
Penicillin
What are the four qualities of a good medicine?
Effective
Safe
Stable
Able to be taken in and removed easily
What three main factors are tested from when developing new frugs?
Toxicity
Efficacy
Dose
How is preclinical testing carried out?
In a lab
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 trial and a double blind trail?
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 thel 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
How do aphids cause damage to plants?
They use their sharp mouthparts to extract sap from the plant phloem, weakening the plant. They are also vectors who can transfer pathogens from diseased plants to healthy plants
How can we reduce the number of aphids?
Chemical pesticides
Biological pest control
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 synthesis 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
Spotted leaves
Decay/rotting
Growths
Malformations of stems/leaves
Discolouration
Presence of pests
What are three way in which plant disease can be identified?
Reference to a gardening website/manual
Lab testing
Monoclonal antibody test kits
Examples of physical defence responses used by plants?
Cellulose cell walls
Tough waxy cuticle on leaves
Outside layer on stem/bark on trees
Leaf fall
Give examples of chemical defence responses used by plants?
Antibacterial chemicals
Poisons
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
