4.1.1- Communicable diseases, Prevention and Immune system Flashcards
what are the 4 different types pathogens that can cause communicable diseases?
- bacteria
- viruses
- protoctista
- funghi
what are communicable diseases?
a disease that is caused by a pathogen and transmitted directly between organisms.
what are bacteria?
Prokaryotic cells that have cell walls but lack organelles. Some bacteria are
pathogenic, producing toxins that damage host cells, or they can remain within body cavities/spaces
what is a virus?
Non-living infectious agents that invade host cells and take over cell metabolism, replicating within them, hijacking their machinery to replicate genetic material and proteins.
They do not have a cellular structure, so they can’t respire, produce ATP or replicate genetic material
what is a protoctista?
A group of unicelllar eukaryotic, single-celled microorganisms that may cause disease.
They digest cells and use the cell contents to reproduce
what is funghi?
Eukaryotic, often multicellular organisms that may cause disease. They digest and destroy cells, and produce spores that can spread rapidly between organisms
they have a similar structure to plants, with cell walls and large vacuoles, but their bodies are made of filaments called hyphae.
what does hyphae do in plants?
hyphae form a network and spread throughout a host/soil
what are the two types of transmission of communicable pathogens?
- direct
- indirect
what is direct transmission?
when the communicable pathogens are transmitted from one host to another host
what is indirect transmission?
when a second organism (vector) that is unaffected by the pathogen transfers it to a new host
what is a vector?
an organism that transports pathogens from one host to another, but is not harmed by the pathogen.
what is disease transmission?
the transfer of pathogens from an infected host to an uninfected host.
what are spores and how are they involved in transmission?
- small reproductive structures that are released into the environment, and are produced through mitosis/meisosis
- they are dispersed via wind/water, when they have reached a food source, they begin growing
what are the 8 factors that affect disease transmission?
- overcrowding
- poor nutrition
- living conditions
- mobile vector
- climate change
- culture/infrastructure
- socioeconomic
- low genetic diversity
what are 4 examples of plant pathogens?
- ring rot (bacteria)
- tobacco mosaic virus (virus)
- potato/tomato late blight (protoctista)
- black sigatoka in bananas (funghi)
what are 7 examples of animal pathogens?
- tuberculosis (bacteria)
- bacterial meningitis (bacteria)
- HIV/AIDS (virus)
- influenza (virus)
- malaria (protoctista)
- ring worm (funghi)
- athletes foot (funghi)
what are the two types of passive defense do plants have against pathogens?
- physical barrier
- chemicals
what is the role of chemical defences in plants?
- they prevent pathogens from growing on plant surface by creating acidic conditions, or kill them
- repel insect vectors for diseases away from plant
what is the role of physical barriers in defences of plants?
to reduce the spread of a pathogen
what are some examples of chemical defences in plants?
- toxic compounds
- enzyme inhibitors
- receptor molecules
- sticky resin in bark
- compounds that encourage the growth of competing microorganisms
what are some examples of physical barriers for defences in plants?
- reinforced cell wall (funghi and bacteria)
- narrowing of the plasmodesmata
- ingrowths into the xylem cell, creates wall made of callose, from cytoplasm growing into xylem
- blockage of the phloem
explain the callose deposition as part of a physical defence in plants?
- invasion of pathogens stimulates release of callose and lignin
- callose= a polysaccharide, forms matrix shape
- callose and lignin is deposited between cell surface membrane and wall, both acting as barriers/lignin is a mechanically stronger barrier
- callose also fills sieve pores of phloem, so phloem sap cannot be transported
- callose reduces size of channels that connect neighbouring plant cells, narrowing plasmodesmata
how do plants recognise a pathogen attack?
- receptors in cells respond to pathogen/chemicals released when cell wall is attacked
- receptors release phytoalexin chemicals, which disrupt pathogen metabolism and bacterial cell surface membranes, delay pathogen reproduction, and stimulate the release of chitinases
- salicylic acid and ethelyne are also released as part of signalling molecules/cell signalling
- cellular responses are triggered, producing defences and strengthening the cell wall.
what are the four methods of defence in animals?
- physical, body tissue act as barriers, preventing the entry of pathogens
- cellular, cells detect/signal presence of pathogens, secreting protective substances
- chemical, secreted substances generate an inhospitable environment for the growth of pathogens, by trapping and bursting them, preventing entry
- commensal organisms, harmless bacteria and funghi compete with pathogens for nutrients
what is the non specific immune system in animals?
the system doesn’t distinguish between different pathogens, so the same response is given each time to the same attacking pathogen.
what does the first/primary line of defence in animals do?
-prevents the entry of pathogens
what are the 4 defences in the primary line of defence?
- skin, acts as a physical barrier to pathogens
- mucous membranes, move bacteria/viruses out of body
- expulsive reflexes, coughing and sneezing
- chemical secretions
how does the skin act as a physical barrier?
- outer layer= hard, dry, dead cells filled with keratin
- there are secretions of sebum that contain fatty acids which have antimicrobial properties
- evaporation of sweat from the skin leaves behind a salt residue
- the lack of moisture, low pH and high salinity creates an inhospitable environment for the growth of microorganisms
how does a mucous membrane protect animals against pathogens?
- line the gut, airways and reproductive system
- membrane consists of epithelial cells, and mucus-secreting cells, mucus is sticky due to glycoproteins/carbohydrate chain
- muscus can trap bacteria/viruses, thenmoved up and out of tubes by cilia
how do expulsive reflexes protect animals against pathogens?
- when a pathogen irritates the lining of an airway it can trigger an expulsive reflex; a cough or sneeze, resulting in a sudden expulsion of air.
- -his expelled air contains secretions from the respiratory tract along with the foreign particles that have entered
what are the two main chemical secretions that occur within animals to protect against pathogens?
- lysozymes= antimicrobial enzymes that breakdown the cell wall of bacteria, found in body fluids such as blood, tears, sweat, and breast milk
- hydrochloric acid= produced by the cells that line the stomach, creating a low pH inside the stomach, helping kill any bacteria that has been ingested alongside food, the cells of the gut secrete mucus to prevent being damaged by hydrochloric acid
what does the 2nd/secondary line of defence in non-specific immunity involve?
phagocytic cells and antimicrobial proteins responding to the invading pathogens
what are the 4 examples involved in the secondary line of defence in non-specific immunity?
- blood clotting
- inflammation
- wound repair
- phagocytosis
what does blood clotting involve?
-a break in mucous membrane/skin, causes release of molecules that trigger a chemical cascade, resulting in blood clotting
what does blood clotting do?
- prevents excess blood loss
- prevents the entry of pathogens
- provides a barrier/scab for wound healing to occur
what does inflammation involve?
- localised response to damage/irritation from pathogen
- pain, warmness, redness and swelling of tissue
- chemical signalling molecules/mast cells, resulting in migration of phagocytes into tissue and increased blood flow
- histamines and cytokines
what does histamines do in terms of inflammation?
- cause vasodilation, increasing blood flow
- ‘leaky’ capillaries allow fluid to enter the tissues and creating swelling, with some plasma leaving the blood
- phagocytes leave the blood and enter the tissue to engulf foreign particles
- cells release cytokines
what does cytokines do in terms of inflammation?
-stimulate inflammation and immune response
what does wound repair involve?
- occurs below the scab formed by blood clotting
- stem cells divide by mitosis to heal wound
what are the 6 steps to wound repair?
- new blood vessels form
- collagen is produced
- granulation tissue forms to fill the wound, made from fibrin fibres
- stem cells move over the new tissue and divide to produce epithelial cells
- contractile cells cause wound contraction
- unwanted cells die
what are phagocytes?
=white blood cells that are involved in the secondary, non-specific response to infection, and are responsible for removing dead cells and invasive microorganisms
what are the two types of phagocytes?
- neutrophils
- macrophages/antigen-presenting cells.
what occurs during phagocytosis?
- pathogen enters, it is recognised as foreign due to it’s antigens
- neutrophils attach to foreign antigens
- receptors on phagocytes bind to antibodies already attached to pathogen, helping attract the phagocyte to site of infection
what is phagocytosis?
the process of recognising and engulfing a pathogen?
what is the mode of action of neutrophils?
- chemicals released by pathogens attract neutrophils to located site, neutrophils move towards pathogens
- receptor proteins on neutrophils recognise antibodies and attach to them
- neutrophil’s cell surface membrane extends around pathogen, engulfing and trapping it
- digestive enzymes destroy pathogen, then neutrophil dies
what is the role of macrophages?
-stimulate immune system
how do macrophages stimulate an immune response?
- break up invading pathogen
- display it’s antigens on it’s surface, recognised as lymphocytes. (known as antigen-presenting cell)
- this initiates an immune response