12.1 - Animal and Plant Pathogens Flashcards
Define disease
An illness or disorder of the body or mind that leads to poor health
Define infectious diseases
- these are diseases caused by organisms known as pathogens
- they are passed from infected to uninflected people
- some also affect animals and are passed from animals to humans
What are some examples of infectious diseases ?
- cholera
- malaria
- HIV/aids
- tuberculosis
Define non infectious diseases
long term degenerative diseases that are not caused by pathogens
What are some examples of non infectious diseases ?
- lung cancer
- chronic obstructive pulmonary disease COPD
- sickle cell anemia
- cystic fibrosis
What are the types of pathogens ?
- bacteria
- fungi
- viruses
- protoctista
What are vectors ?
Carry pathogens from one organism to another
What are some common vectors ?
- water
- insects
What is a pathogen ?
A microorganism that causes disease
How do bacteria cause disease ?
By destroying cells and releasing waste products and/ or toxins
What are the two ways bacteria can be classified ?
- By their basic shapes
- By their cell walls
What are the 5 different shapes bacteria can be ?
- they may be :
- rod shaped ( bacilli )
- spherical ( cocci )
- comma shaped ( vibrios )
- spiralled ( spirilla )
- corkscrew ( spirochaetes )
What are the two types of bacterial cell walls ?
- gram positive bacteria
- gram negative bacteria
How do these two bacterial cell walls differ ?
- have different structures
- react differently with a process called gram staining
What happens when staining gram positive bacteria ?
- look purple- blue under the light microscope
- for eg. Methicillin- resistant staphylococcus aureus ( MRSA )
What happens when staining gram negative bacteria ?
- appear red
- eg. Gut bacteria E.coli
Why is it key to identify between the different cell walls ?
type of cell wall affects how bacteria react to different antibiotics
What are some features of a gram positive cell wall excluding colour with gram staining ?
- thicker but less tough
- more susceptible to antibiotics which damage the cell wall
- more peptidoglycan
- lower lipid content
- more prominent mesosome
What makes a gram- positive cell wall go purple- blue with gram staining ?
The peptidoglycan in their cell wall retains crystal violet stain
What are some features of a gram negative cell wall ?
- thinner but tougher
- higher lipid content due to outer cell membrane
- less susceptible to antibiotics
What are viruses ?
Non- living infectious agents
How large is a virus diameter ?
0.02-0.3 diameter
What is the basic structure of a virus ?
Some genetic material either DNA or RNA surrounded by a protective protein coat
What is the mechanism of infection of a virus ?
- they attach to the cell and inject their genetic material
- this takes over their biochemistry of the boar cell to make more viruses
- this is via inserting itself into the host DNA
- until so many are made that the host cell is lysed ( bursts)
- and new viruses are released
What 2 things make viruses very successful pathogens ?
- reproduce rapidly
- evolve by developing adaptations to their host
What proportion of naturally occurring viruses are pathogenic ?
All of them
What is a bacteriophage ?
A virus which attacks a bacteria
- take over bacterial cells and use them to replicate
- destroying the bacteria at the same time
What is a virophage and give a example ?
- a virus which infects other viruses
- eg. Sputnik virus
Are protoctistia eukaryotic ie prokaryotic ?
- Eukaryotic
- with a vide variety of feeding methods
Are protocistia unicellular or multicellular ?
- Unicellular
- they can group into colonies
What type of protists cause disease ?
Parasitic
What is meant by parasitic ?
They use people or animals as their host organism
What are pathogenic protists ?
Need a vector to transfer them to their hosts
Are fungi multicellular or unicellular ?
- usually multicellular
- with the exception of yeasts
How do fungi feed ?
- many fungi are saprophytes meaning they feed on dead and decaying matter
- some fungi are parasitic meaning they feed on living plants and animals
- fungi cannot photosynthesise and they digest food extracellular lay before absorbing the nutrients
How do fungi reproduce ?
- produce millions of spore
- can spread through huge distances and spread their distances quickly among crops
What organelles do yeast have ?
- nucleus
- mitochondria
- cell membrane
- permanent vacuole
What are the two main pathogenic modes of action ?
- Damaging host tissues directly
- Producing toxins which damage host tissue
How do fungi damage the tissues of their host organism ?
- digest living cells and destroy them
- this combined with the response of the body to the damage caused by the fungus gives the symptoms of disease
How do protoctista damage the host cells directly ?
- take over cells and break them open as the new generation emerge
- they do not take over the genetic material of the cell
- simply digest and use the cell contents as they reproduce
How do viruses damage the host tissues directly ?
- take over cell metabolism
- the viral genetic material gets into the host cell and is inserted into the host DNA
- the virus them uses the host cell to make new viruses which then burst out of the cell destroying it
- then do read it infect other cells
How do bacterial toxins damage host cells ?
- by breaking down the cell membranes
- some damage or inactive enzymes and some interfere with the host cell genetic material so the cells cannot divide
- these toxins are a by- product of the normal functioning of the bacteria
