Communicable Diseases Flashcards
State the types of organism that can act as pathogens
- Bacteria
- Viruses
- Protoctists
- Fungi
Describe bacteria and how they act as pathogens
- Bacteria are prokaryotic cells
- They can be identified by different shapes (rod, spherical, comma-shaped, spiral, corkscrew)
- Bacteria can have gram-negative or gram positive cell wall
- Bacteria can produce toxins which damage host cells
- Host organism defences towards the bacteria may also cause damage to host cells and tissues
Describe viruses and how they act as pathogens
- Viruses are not cellular organisms
- They are infectious structures composed of DNA or RNA surrounded by protein
- They can infect eukaryotic and prokaryotic cells (depending on the type)
- They enter host cells and use their organelles to produce more viral particles
- Which go on to infect more host cells
- This causes destruction of the infected cells
Describe fungi and how they act as pathogens
- Fungi are eukaryotic organisms that can be uni- or multicellular
- Fungi are not autotrophic so need to obtain nutrients from their environment
- They release digestive enzymes onto their host organism
- And absorb the digestion products in order to grow and carry out respiration
- Digestion of host cells and tissues causes harm to the host organism
- Some fungi also produce toxins
Describe protoctists and how they act as pathogens
- Protoctists are unicellular eukaryotic organisms
- Some protoctists act as pathogens of plant or animal organisms
- Pathogenic protoctists infect cells and use the cellular contents as their nutrition to grow and multiply
- They burst out of the host cell and infect other cells
Give examples of bacterial pathogens and the diseases they cause
![](https://s3.amazonaws.com/brainscape-prod/system/cm/322/212/975/a_image_thumb.png?1601292740)
Give examples of viral pathogens and the diseases they cause
![](https://s3.amazonaws.com/brainscape-prod/system/cm/322/213/232/a_image_thumb.png?1601292974)
Give examples of fungal pathogens and the diseases they cause
![](https://s3.amazonaws.com/brainscape-prod/system/cm/322/213/472/a_image_thumb.png?1601293068)
Give examples of protoctist pathogens and the diseases they cause
![](https://s3.amazonaws.com/brainscape-prod/system/cm/322/213/484/a_image_thumb.png?1601293117)
State the main types of direct transmission of pathogens between host organisms
- Direct transmission is when the pathogen is transferred directly from one host body to another. Ways in which direct transmission can occur are:
- Direct contact, including kissing, skin-to-skin contact, from faeces to hands
- Inoculation, including through breaks in skin, animal bites, sharing needles
- Ingestion, including contaminated food or drink, transfer from hands to mouth
- In plants, direct contact can be from part of an infected plant to another
State the main types of indirect transmission of pathogens between host organisms
- Indirect transmission is the transfer of pathogen from one individual to another, that requires some surface, substance or organism. Examples are:
- Fomites, inanimate objects such as clothing or door handles that transfer the pathogen between individuals
- Droplet infection, is where mucus droplets from one infected individual are inhaled by another
- Vectors are substances or organisms in which the pathogen can be moved from an infected individual to an uninfected one. Examples include:
- Wind
- Water
- Animals
- Human transfer (through clothing, machinery, skin)
State the factors which affect the transmission of communicable diseases in animals
- Overcrowding
- Poor nutrition
- Weak or weakened immune system (very young or elderly individuals)
- Poor waste disposal
- Climate change
- Culture and infrastructure
- Socioeconomic factors
State the factors which affect the transmission of communicable diseases in plants
- Some crop varieties are genetically susceptible to disease
- Planting too close together
- Poor mineral supply can reduce plant health
- Damp, warm conditions may favour pathogens
- Climate change (more rain, more wind: more vector)
Describe how plant cells may detect and make a response to a pathogen
- Substances produced by the pathogen are detected by the receptor proteins in plant cell membranes
- Signaling molecules are produced inside the plant cell that alert the nucleus
- Nucleus activates production of physical or chemical defences
- This can prevent the spread of pathogen to uninfected parts of the plant
Describe the physical defences of plant cells to pathogens
- Plant cells deposit more of the carbohydrate callose between cell walls
- Callose blocks the sieve plates in the phloem
- Callose blocks the plasmodesmata between plant cells
- This prevents uninfected cells from getting infected
- Lignin is then also deposited in the cell walls
- These processes strengthen barriers between cells to prevent the spread of the pathogen
Describe the chemical defences of plants
- Chemical defences are substances produced by plants that act against the sources of infection or damage
- Examples include:
- Insect repellents
- Insecticides
- Antibacterial compounds
- Antifungal compounds
- Anti-oomycetes (act against protoctist pathogens)
- General toxins (produced at levels only harmful to pathogens)
Describe the non-specific defences of animals that prevent the entry of pathogens
- Skin, a physical barrier that prevents pathogens from accessing living cells and tissue underneath
- Mucous membranes which:
- Lysozyme is present in body fluids such as tears, urine
- Trap and remove pathogens in mucus
- Release lysozyme to break down pathogen cell walls
- Contain many phagocytes
- Gut and skin bacteria that prevent the survival of pathogens
- Highly acidic environment in the stomach
- Expulsive reflexes that allow removal of pathogens trapped in mucus
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