B5 Communicable Diseases Flashcards
Health
A state of physical and mental wellbeing
Factors that have an effect on health
Diet, stress and life situations
Viruses living in cells can trigger changes that can
Lead to cancers
Defects in the immune system due to infections, poor nutrition or genetic makeup can
Make you more likely to suffer from other communicable diseases
Immune reactions initially caused by a pathogen can
Trigger allergies to factors in the environment
Severe physical ill health can lead to
Depression and other mental illness
Difference between viruses and bacteria
Viruses are smaller than bacteria and unlike viruses, some bacteria are useful
Positive uses of bacteria
Make food such as yogurt and cheese, treat sewage, and make medicines
How do bacteria cause disease?
They divide rapidly by splitting in two (binary fission) and produce toxins that affect the body and make you feel ill
How do viruses cause disease?
They take over the cells of your body. They live and reproduce inside the cells, damaging and destroying them
Common disease symptoms
High temperature, headaches, and rashes
How are pathogens spread?
By air, direct contact, and by water
Culture medium
A liquid or gel containing nutrients
Mutation
A change in the DNA
What is the maximum temp at which cultures can be incubated in schools and colleges?
25 degrees c
Why does bacteria have to be incubated at 25 degrees c max in schools and colleges?
If the bacteria was cultured at 37 degrees c (human body temp), there would be a high risk of growing some dangerous pathogens
Why are uncontaminated cultures of microorganisms needed?
To investigate the action of disinfectants and antibiotics
What factors affect the growth rate of bacteria?
Temperature, available nutrients, oxygen levels, and pH
Bacteria at the end of the growth period =
Bacteria at the beginning of the growth period x 2^number of divisions
Antiseptic
A dissinfectant that is safe to use on human skin
Ways to prevent bacterial growth
Change the temperature, disinfectants, antisepctics, and antibiotics
How to investigate the effect of disinfectants and antibiotics
You can add circles of filter paper soaked in different types of disinfectant or antibiotic when you set up the culture plate. The zone of inhibition can be measured to investigate the effect of the different antiseptics/antibiotics on the growth of the bacteria
Ways to prevent infections
Simple hygiene measures, isolating infected individuals, destroying vectors, and vaccination
Symptoms of measles
Fever and a red skin rash
How is measles spread?
Inhalation of droplets from coughs and sneezes (airborne) and is very infectious
How is HIV/AIDS spread?
Direct sexual contact and the exchange of bodily fluids. Can also be passed from mother to child in breast milk.
Symptoms of HIV/AIDS
HIV only causes mild, flu-like symptoms to begin with. It attacks the immune system and remains hidden inside the immune system until the immune system is so badly damaged that it can no longer deal with infections or certain cancer (at this point the patient has developed AIDS)
How to treat measles
There is no treatment for measles so infected patients need to be isolated to stop the spread
How to treat HIV/AIDS
There is no cure and no vaccine however the regular use of antiretrovial drugs can prevent the development of AIDS for many years
Symptoms of tobacco mosaic virus
Causes a distinctive mosaic pattern of discoloration on the leaves as the virus destroys the cells. This affects the growth of the plant as the affected areas of the leaf do not photosynthesise
How is tobacco mosaic virus spread?
Contact between diseased plant material and healthy plants and insects can act as vectors
How to treat tobacco mosaic virus
There is no treatment and farmers now grow TMV-resistant strains of many crop plants. Good field hygiene and good pest control can help prevent the spread
Name three viral diseases
Measles, tobacco mosaic virus, and HIV/AIDS
Name three bacterial diseases
Salmonella food poisoning, gonorrhoea, and agrobacterium tumefaciens
Symptoms of salmonella
Fever, abdominal cramps, vomiting, and diarrhoea
What is salmonella
Salmonella are bacteria that live in the guts of many different animals. They can be in raw meat, poultry, eggs, and egg products. If they get into our bodies they disrupt the balance of the natural gut bacteria and can cause salmonella food poisoning
How to treat salmonella
For many people salmonella infections don’t last long and no antibiotics are given. In the Uk poultry are vaccinated against salmonella to control the spread
How is gonorrhoea spread?
Unprotected sexual contact with an infected person
Symptoms of gonorrhoea
Thick yellow or green discharge from the vagina or penis and pain on urination.
If untreated: long-term pelvic pain, infertility, and ectopic pregnancies
How to treat gonorrhoea
Can be treated with antibiotics. Originally it was easily cured with penicillin but now many resistant strains have evolved so it is increasingly difficult to treat
Bacterial diseases in plants
There are few bacterial diseases in plants. Agrobacterium tumefaciens is a bacterium that causes crown galls-a mass of unspecialised cells that often grow at the join between the root and the shoot in infected plants
Fungal diseases in people
There are relatively few. Athlete’s foot is a well known, minor fungal skin condition. Antifungal drugs are usually effective against skin fungi, but it can be hard to treat deep-seated tissue infections
Symptoms of rose black spot
It causes purple or black spots to develop on the leaves. They often turn yellow and drop early and this weakens the plant because it reduces the area of leaves available for photosynthesis and as a result the plant doesn’t flower well
How is rose black spot spread?
The spores of the fungus are spread in the environment, carried by the wind. They are then spread over the plant after it rains in drips of water that splash from one leaf or plant to another
How to treat rose black spot
Gardeners try to prevent the spread by removing and burning affected leaves and stems. Chemical fungicides can also help to treat the disease and prevent it spreading. Horticulturists have bred types of roses that are relatively resistant to black spot but the disease still cannot be prevented or cured
Example of a protist disease
Malaria
What is a protist?
A single-celled organism
Symptoms of malaria
They affect the liver and damage red blood. It causes recurrent episodes of fever and shaking when the protists burst out of the blood cells and it can be fatal
How is malaria spread?
The bite of female mosquitos
How to treat malaria
If diagnosed quickly, it can be treated using a combination of drugs however some protists have become resistant to the most commonly used medicines
How to prevent the spread of malaria
Use insecticide-treated mosquito nets, use insecticides to kill mosquitos, prevent the vectors from breeding by removing standing water and spraying water with insectices to kill the larvae, and travellers can take antimalarial drugs that kill the parasites in the blood if they are bitten by an infected mosquito.
Skin defences of humans
The skin acts as a barrier, it produces antimicrobial secretions to destroy pathogenic bacteria, and healthy skin is covered with microorganisms that help to keep you healthy and act as an extra barrier
Human defences of the respiratory system
The nose is full of hairs and produces mucus which trap particles in the air that may contain pathogens of irritate your lungs. The trachea and bronchi also secrete mucus to trap pathogens from the air. The lining of the tubes is covered in cilia which beat to waft the mucus up to the back of the throat where it is swallowed.
Human defences of the digestive system
The stomach produces acid which destroys the microorganisms in the mucus you swallow, as well as the majority of pathogens you take in from food and drink
Human defences in the immune system
Some white blood cells ingest pathogens, digesting and destroying them. Some produce antibodies which target particular bacteria or viruses and destroy them. Some white blood cells produce antitoxins which counteract the toxins released by pathogens
Why are aphids so damaging?
They bite into the plants’ phloem vessels and deprive the plant cells of the products of photosynthesis. They can also act as vectors and transfer viruses, bacteria, and fungi
How to stop aphids
They can be destroyed using chemical pesticides or, in enclosed spaces, biological pest control. Aphid eating insects such as ladybirds can be released to control the pathogen population
Nematode worms and many insect larvae…
Live in the soil and feed in or on plant roots, damaging them so they cannot absorb water and mineral ions effectively
Chlorosis
Plants take magnesium ions from the soil to make the chlorophyll needed for photosynthesis. If the level of magnesium ions in the soil is low, the plant cannot make enough chlorophyll. The leaves become yellow and growth slows down
Plants need a good supply of nitate ions from the soil to…
Convert the sugars made in photosynthesis into proteins needed for growth in protein synthesis. A nitrate deficiency will cause stunted growth
What causes stunted growth?
Nitrate deficiency
What causes spots on leaves?
Black spot fungus on roses
What causes areas of decay or rotting?
Black spot on roses, blights on potatoes
What causes growths in plants?
Crown galls caused by bacterial infections
What causes malformed stems and leaves?
Due to aphid or nematode infestation
What causes discolouration?
Yellowing or chlorosis in magnesium deficiency, mosaic patterns resulting from tobacco mosaic virus
How can plant diseases be detected
Gardening manuals/online, DNA analysis of diseased materials, and monocolonal antibodies test kits that can identify the presence of certain pathogens
Physical barriers against pathogens in plants
cellulose cell wall, tough waxy cuticle, bark on trees and leaf fall
Chemical barriers against pathogens in plants
many plants produce antibacterial chemicals that protect them against invading pathogens. As current antibiotics are becoming less effective, scientists are investigating whether these chemicals can be used as antibiotics
Plant defences against herbivores
poisons to deter, thorns to make it painful to eat them, hairy stems and/or leaves, drooping or curling when touched, and mimicry
