4.1 - communicable diseases Flashcards
What are the categories of disease?
- infectious
- deficiency
- inherited
- mental disorder
- social disease
What are communicable diseases?
Infectious diseases spread by pathogens
Pathogens include: bacteria (prokaryotes), viruses, fungi and protoctista.
What are the main communicable diseases?
Bacteria
Tuberculosis (TB), bacterial meningitis, ring rot (potatoes, tomatoes)
Virus
HIV/AIDS (human), Influenza (animals), Tobacco mosaic virus (plants)
Protoctista
Malaria, Potato/tomato late blight
Fungi
Black sigatoka (bananas), ringworm (cattle), athlete’s foot (humans)
What are the cycles of the virus?
lytic and lysogenic
What is a virus?
A non-living pathogenic small invading host cell
What is a virus that attacks bacteria?
bacteriophages, they take over the bacterial cell and use it to replicate as bacteria have a very fast rate of reproduction.
What is a bacteria?
Very small cells
Rapidly reproduce every 20 minutes
Release toxic waste products
Prokaryotic
no membrane-enclosed nucleus
carry out respiration but not in mitochondria or chloroplasts a single chromosome
a closed circle of double-stranded DNA with no associated histones
if flagella are present, they are made of a single filament of the protein flagellin
have smaller ribosomes than other groups
What is a protoctista?
Now widely known as protista
Eukaryotic with a wide variety of feeding mechanisms.
Protists that cause disease are parasitic that is they use a host to feed from.
May need a vector to transfer them to their hosts e.g malaria transferred to host by mosquito.
What is a fungi?
Eukaryotic
Most are multicellular organisms although the yeast that causes thrush is unicellular.
Not a major problem in humans but cause devastation in plants.
Digest their food externally before absorbing the nutrients (example of extracellular enzyme action).
Many fungi are saprophytes which means they feed on dead decaying material.
Have hyphae which can produce spores which allows them to spread rapidly through crops.
What is direct transmission?
passing a pathogen from host to new host with no intermediary
What is indirect transmission?
passing a pathogen from host to new host via a vector
Examples of direct transmission
Viruses – Hijack cellular machinery by inserting their genetic material into the host cell and then into the host DNA. The host cell then makes new copies of the virus which hen burst out of the cell destroying it and then spreading it to neighboring cells.
Protoctista – also take over cells and break them open. They simply digest the contents of the host cell and absorb the nutrients to reproduce.
Fungi – digest living cells and destroy them. The response of the body to the damage gives the symptoms of the disease.
Examples of indirect transmission
Bacteria – produce toxins that poison or damage the host cells in some way
break down cell membranes
inactivate enzymes
interfere with host genetic material and cell division
These toxins are a byproduct of the normal functioning of the bacterial cell.
Fungi – some produce toxins which affect host cells and cause disease.
what are the physical plant defenses?
cellulose cell wall
lignin thickening
waxy cuticle
bark
stomatal closure
callose in sieve tube
tylose in xylem
what are chemical plant defenses?
cell walls additional cellulose
callose deposition
oxidative bursts
increase in chemicals
