Biology Topic 7 Communicable Diseases Flashcards
Pathogens definition
Pathogens are microorganisms that cause infectious disease: viruses, bacteria, protists or fungi.
Pathogens how there spread and what they infect
Pathogens may infect plants or animals and can be spread by direct contact, water or air.
Summary of what bacteria do to the body
Bacteria reproduce rapidly inside the body and may produce poisons (toxins) that damage tissues and make us feel ill.
Summary of what viruses do to the body
Viruses reproduce inside cells, causing cell damage. (Viruses are not living and are not made of cells).
how is it spread?
Measles
Spread by inhalation of droplets from sneezes and coughs. Symptoms of fever and red skin rash. Can be fatal if complications arise. Most young children are vaccinated against measles.
HIV
HIV - Spread by sexual contact or exchange of bodily fluids such as blood, which can occur when drug users share needles. Initially causes flu-like symptoms. Unless successfully controlled with antiretroviral drugs the virus attacks the body’s immune cells. Late stage HIV, or AIDS, occurs when the body’s immune system becomes so badly damaged it can no longer deal with other infections or cancers.
TMV
Tobacco Mosaic Virus - Gives a distinctive ‘mosaic’ pattern of discolouration on the leaves, which affects the growth of the plant due to lack of photosynthesis. Widespread plant pathogen affecting many species of plant eg. tomatoes
Salmonella
Salmonella - food poisoning spread by bacteria ingested in food, or on food prepared in unhygienic conditions. Symptoms of fever, abdominal cramps, vomiting and diarrhoea are caused by the toxins secreted by the bacteria. In the UK, poultry are vaccinated against Salmonella to control spread.
how to treat and control spread what symptoms and what type of disease
Gonorrhoea
Gonorrhoea - STD causing symptoms of thick yellow or green discharge from the vagina or penis and pain when urinating. Easily treated with the antibiotic penicillin. Spread can be controlled by using barriers methods of contraception eg. condoms
treatment? what is does to plant?
Rose black spot
Rose black spot - purple or black spots develop on leaves. Leaves often turn yellow and drop early. Affects the growth of plants as photosynthesis is reduced. Fungal spores are spread by water or wind. Can be treated using fungicides and / or removing and destroying infected leaves.
Malaria
Malaria - Symptoms of recurrent episodes of fever, which can be fatal. Spread is controlled by preventing the mosquito vectors from breeding and by using mosquito nets to avoid being bitten.
The spread of diseases can be reduced or prevented by:
simple hygiene measures eg. hand washing
destroying vectors eg. insects
isolation of infected individuals
vaccination.
triple only definition of how bacteria multiply
Bacteria multiply by simple cell division (binary fission) as often as once every 20 minutes if they have enough nutrients and a suitable temperature.
How can bacteria be grown and why
Bacteria can be grown in a nutrient broth solution or as colonies on an agar plate. Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics.
Describe how to prepare an uncontaminated culture using aseptic technique and why :
first sterlise all Petri dishes and culture media bacteria broth and agar before use must be sterilised before use this kills any unwanted microrganisms and it prevents contamination.
then clean bench with disinfectant solution this kills microorganism that could contaminate our culture .
Inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame.
open a sterile agar plate near a bunsen burner flame , the flame kills bacteria in the air
now use the loop to spread the bacteria that had been chosen evenly over the plate.
place sterile paper discs containing antibiotics onto the plate.
The lid of the petri dish should be secured with adhesive tape( stops lid from falling off and any unwanted microorganisms from entering) and stored upside down to prevent condensation damaging the agar.
In school labs, cultures should generally be incubated at a maximum of 25℃ which reduces the chances that harmful bacteria will grow
Describe non-specific defence systems of the human body against pathogens:
Skin - Barrier, produces antimicrobial secretions
Nose - hairs and mucus to trap particles that may contain pathogens
Trachea & bronchi - secrete mucus which traps pathogens, cilia waft mucus to back of throat
Stomach - produces acid which kill the majority of pathogens
Explain the role of the immune system in the defence against disease.
Phagocytosis (phagocytes engulf and digest pathogens)
Lymphocytes release antibodies which attach to antigens on a pathogen / cell
Antitoxin production
Memory cells divide and release antibodies quickly in response to a second infection by the same pathogen
what is vaccination
Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies.
herd immunity definition
If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced.
Antibiotics summary
Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body. Antibiotics cannot kill viral pathogens. Specific bacteria should be treated by specific antibiotics. The emergence of strains resistant to antibiotics is of great concern.
Painkillers and other medicines are used to
treat the symptoms of disease but do not kill pathogens.
why can’t viruses be easily killed ?
It is difficult to develop drugs that kill viruses as they reproduce inside body cells. Drugs would therefore also damage the body’s tissues.
Plant diseases can be detected by these symptoms:
Stunted growth
Spots on leaves
Areas of decay
Growths
Malformed stems or leaves
Discolouration
Presence of pests
Identification of plant diseases can be made by:
Reference to a gardening manual or website
Taking infected plants to a laboratory to identify the pathogen
Using testing kits that contain monoclonal antibodies
Plants can be infected by a range of pathogens:
: viral (tobacco mosaic virus), bacterial and fungal (black spot) as well as by insects (aphids).
Plants can be damaged by a range of ion deficiency conditions:
Nitrate deficiency - stunted growth as nitrate ions are needed for protein synthesis and therefore growth
Magnesium deficiency - chlorosis as magnesium ions are needed to make chlorophyll
Physical defence responses resist invasion from microorganisms in plants
Cellulose cell walls
Tough waxy cuticle on leaves
Layers of dead cells around stems (bark on trees) which fall off
Mechanical adaptations defend against animals in plants
Thorns and hairs deter animals
Leaves which droop or curl when touched
Mimicry to trick animals
Chemical defence responses in plants
Antibacterial chemicals eg. mint and witch hazel
Poisons to deter herbivores eg. tobacco plants, foxgloves, deadly nightshade
broth is cloudy because it contains
a very large amount of bacteria
Two examples of bacteria cultures
agar gel plate
nutrient broth solution
how do agar gel plates work
they contain nutrient broth which has been set into a jelly using a chemical called agar this is then poured into a petri dish and left to set
on an agar plate bacteria grow in
bacterial colonies
It is really important when concerning an agar plate that we avoid contamination because there are lots of ———————————
microorganisms such as bacteria and fungi naturally in the environment and these could easily contaminate our cultures
After a few days the plate :
around the antibiotics we have a region where the bacteria have not grown this is called the zone of inhibition
to find the zone of inhibition we use the equation
pie r squared
