4.1.1 - Disease and the Immune System Flashcards
What is a communicable disease?
a disease caused by pathogens that can be passed from one organism to another
-are infectious
What are the 4 types of pathogens?
- bacteria
- viruses
- protoctista
- fungi
What are the 2 types of bacteria?
Gram positive bacteria
-look purple-blue (after gram staining) under light microscope
Gram negative bacteria
-look red (after gram staining) under light microscope
How do bacteria cause disease?
by producing toxins that poison or damage the host cells
eg. by breaking down cell membrane or interfering with genetic information
Are bacteria eukaryotes or prokaryotes?
prokaryotes
Name 3 examples of bacterial diseases
ringrot
tuberculosis
bacterial meningtisis
What type of pathogen causes ringrot?
bacteria
What type of pathogen causes tuberculosis?
bacteria
What type of pathogen causes meningtisis?
bacteria
What is the basic structure of viruses?
genetic material surrounded by protein
0.02-0.3μm
How do viruses cause disease?
By invading cells and taking over the cell’s mechanism
They insert their genetic information into the cell’s DNA
The virus uses the cell to produce new viruses, which burst out of the cell (destroying that cell) into other cells
What are bacteriophages?
viruses that attack bacteria by taking over their cells and using them to replicate, which destroys the bacteria in the process
Name 3 examples of viral diseases
TMV (tobacco mosaic virus)
HIV (AIDS)
Flu/influenza
What type of pathogen causes TMV?
virus
What type of pathogen causes HIV (AIDS)?
virus
What type of pathogen causes flu/influenza?
virus
Are protoctista eukaryotes or prokaryotes?
eukaryotes
How do protoctista cause disease?
By taking over cells and breaking them down by digesting and using the cell’s contents
Name 2 examples of protoctisa diseases
malaria (the protist is mosquito)
potato blight
What type of pathogen causes malaria?
protoctista
What type of pathogen causes potato blight?
protoctista
Are fungi eukaryotes or prokaryotes?
eukaryotes
How do fungi cause disease?
By digesting and destroying living cells
-some produce toxins that affect the host cells and cause disease
Name 3 examples of fungal diseases
black sigatoka
ring worm
athlete’s foot
What type of pathogen causes black sigatoka?
fungus
What type of pathogen causes ring worm?
fungus
What type of pathogen causes athlete’s foot?
fungus
What is direct transmission?
when the pathogen is directly transferred from one organism to another
What is indirect transmission?
when the pathogen travels from one organism to another through something else
Name the 6 methods of transmission in animals
direct contact (contagious disease) inoculation ingestion fomites droplet infection (inhalation) vectors
Describe how direct contact transmission can happen in animals
- skin to skin contact
- contact with bodily fluids of another person (eg. by kissing, sexual reproduction)
- microorganisms from faeces
Describe how inoculation (transmission) can happen in animals
- break in the skin
- animal bites
- puncture wounds, sharing needles etc
Is inoculation direct or indirect transmission?
direct
Describe how ingestion (transmission) can happen in animals
-taking in contaminated food/drink
Is ingestion direct or indirect transmission?
direct
Describe how fomites (transmission) can happen in animals
-inanimate objects transfer pathogens
Are fomites direct or indirect transmission?
indirect
Describe how droplet infection (transmission) can happen in animals
-tiny droplets of saliva/mucus come out of mouth as you speak/cough/sneeze. If they contain pathogens and people breathe them in, they will become infected
Is droplet infection direct or indirect transmission?
indirect
Describe how vectors (transmission) can happen in animals
-transmit pathogen from one host to another
Are vectors direct or indirect transmission??
indirect
Describe how direct transmission can happen in plants
-contact of a healthy plant with a diseased plant
Describe how soil contamination (transmission) can happen in plants
- infected plants leave pathogens (bacteria or virus) or reproductive spores from pathogens (from fungi or protisits) in soil
- this can affect the next crop that is grown in that soil
Is soil contamination direct or indirect transmission?
indirect
Describe how vectors (transmission) can happen in plants
- pathogens carried by wind
- spores swim on water
- animals carry pathogens
- humans (hands, clothing, farming products, etc)
What factors affect the chance of animals catching a communicable disease?
- living conditions (eg. overcrowding)
- climate
- socioeconomic factors (eg. lack of trained health workers)
- poor nutrition
- poor disposal of waste
How to plants recognise an attack from a pathogen?
receptors in cells detect pathogen or chemicals pathogen has produced
-this stimulates the release of signal molecules and causes responses
How do plants respond to pathogens?
- send alarm signals to unaffected cells
- physically strengthen cell walls
- produces chemicals eg.
- produces callose (polysaccharide that seals of infected areas and strengthens cell walls)
- produces ligin (strengthens barriers)
What chemicals do plants produce to defend themselves against pathogens?
- callose
- ligin
- insect repellants
- insecticides
- antibacterial compounds containing antibiotics
- antifungal compounds
- anti oomycetes
- general toxins
What does callose do?
- seals off infected cells from rest of plant
- strengthens cell walls
- seals off sieve plates in phloem and plasodesmata between cells
What are the primary non-specific defences against pathogens in animals?
- skin
- mucous membranes
- blood clotting
- inflammation
- expulsive reflexes
- lysozymes
What does skin do to prevent the entry/spreading of pathogens?
- covers entire body
- has lots of healthy microorganisms (flora) that outcompete with pathogens for space on body surface
- produces sebum (oily substance that inhibits pathogen growth)
What do mucous membranes do to prevent the entry/spreading of pathogens?
-line body tracts (eg. airways in gas exchange system) and produce mucus (which contains phagocytes and lysozymes and traps organisms)
What are lysozymes?
- enzymes found in tears, urine and stomach acid
- destroy bacterial/fungal cell walls
What are expulsive reflexes and how do they prevent the entry/spreading of pathogens?
-coughs
-sneezes
eject mucus (containing pathogens) from gas exchange system
-vomiting
-diarrhoea
expel contents of gut alongside any pathogens
How does blood clotting prevent the entry/spreading of pathogens?
rapidly seals wounds by platelets forming scabs that pathogens can not get through
How does inflammation prevent the entry/spreading of pathogens?
- red swelling of tissue
- activates most cells, causing them to release histamines and cytokines
- histamines dilate blood vessels, which causes temperature to raise to prevent pathogens reproducing
- cytokines attract phagocytes
How does a fever prevent the entry/spreading of pathogens?
- body temp increases, stopping the reproduction of pathogens
- immune system also works faster at higher temp
What are phagocytes?
white blood cells that engulf and destroy pathogens through phagocytosis
What are the two types of phagocytes?
neutrophils
macrophages
What are neutrophils?
phagocytes made in the bone marrow which have a multi-lobed nucleus and are found in the blood
What are macrophages?
large phagocytes made in the bone marrow
-they travel in the blood as monocytes, settle in lymph nodes and develop into macrophages
Explain the stages of phagocytosis
- phagocytes recognise antigens on pathogen’s cell surface membrane and identify the pathogen as non-self
- phagocyte binds to pathogen
- phagocyte engulfs the pathogen
- pathogen becomes enclosed in a vacuole in the phagocyte and is called a phagosome
- lysosomes in the cytoplasm of the phagocyte move towards the phagosome and combine with it, forming a phagolysosome
- enzymes from lysosome are released to digest and destroy the pathogen
- digested pathogen is absorbed into the cytoplasm of phagocyte
What do macrophages do at the end of phagocytosis? (which neutrophils do not)
- antigens from pathogen’s surface membrane combine with MHC (glycoprotein) in cytoplasm
- MHC moves antigens to the macrophage’s surface
- cell becomes an antigen presenting cell (APC), which alerts the immune system without being a threat
What do cytokines do?
- signal and attract phagocytes
- increase body temp
- stimulates specific immune response
What do opsonins do?
-bind to pathogens and tag them so that they are easily recognised by phagocytes
What are antibodies?
Y shaped glycoproteins that bind to a specific antigen
What is formed when an antibody binds to an antigen?
antigen-antibody complex
What are the antigen binding sites in an antibody?
the site where it binds to the antigen
What is the function of the variable region in an antibody?
gives antibody its specificity for an antigen
What is the function of the disulfide bridge in an antibody?
holds the polypeptide chains in shape
What are the 4 ways an antibody works to defend the body (once it has formed an antigen-antibody complex)?
- antibody in complex acts as opsonin -is easily engulfed and digested by phagocytes
- most pathogens can’t invade body when they’re part of an antigen-antibody complex
- antibody acts as an agglutinin -causes pathogens carrying complexes to clump together (can’t spread so much + phagocytes can engulf multiple at once)
- antibody acts as antitoxin -binds to toxins produced to make them harmless
What do agglutinins do?
bind to several antigens so that they clump together
- can’t spread much
- phagocytes can engulf multiple pathogens at once
What do antitoxins do?
bind to toxins to make them harmless
What are lymphocytes?
white blood cells involved in the specific immune system
What are the two types of lymphocytes?
B lymphocytes
T lymphocytes
- both produced in bone marrow
- B mature in bone marrow but T mature in thymus gland
What are the types of T lymphocytes?
- T helper cells
- T killer cells
- T memory cells
- T regulator cells
What do T helper cells do?
produce interleukins (which stimulate B cells to increase antibody production)
What do T killer cells do?
secrete perforin (which kills the pathogen by making holes in its cell membrane)
What do T memory cells do?
provide immunological memory
-live for a long time
What do T regulator cells do?
suppress the immune system (control and regulate it)
-stops immune system once pathogen has been eliminated to make sure the body doesn’t have an autoimmune response (start attacking its self antigens)
What do B effector cells do?
divide to form plasma cells
What do plasma cells do?
produces and releases antibodies specific to a particular antigen
What do B memory cells do?
provide immunological memory
-live for a long time
What happens in cell mediated immunity?
- macrophage destroys a pathogen and becomes an antigen presenting cell (APC)
- a specific T helper cell has receptors that compliment the antigens on the APC
- these specific T helper cells bind to the antigens (so that the T helper cell becomes activated)
- T helper cells produce interleukins which stimulate more T helper cells to divide via mitosis to produce clones
- clones develop into T helper and T memory cells
- interleukins also stimulates phagocytosis and B cells to divide
What happens in humoral immunity?
- B cell binds to pathogen’s antigen, engulfs the pathogen and processes the antigens to become an antigen presenting cell (APC)
- an activated T helper cell binds to the B cell (clonal selection)
- B cell divides by mitosis (clonal expansion)
- B cells differentiate into B plasma cells and B memory cells
- B plasma cells produce antibodies
- B memory cells provide immunological memory
What are the differences between cell mediated and humoral immunity?
- cell mediated responds to changes in cells
- humoral responds to antigens outside of cells
- cell mediated mainly involves B cells
- humoral mainly involves T cells
- cell mediated detects cells altered by viruses
- humoral detects pathogen’s antigens
What is clonal selection?
an antibody on a B-cell binds to a complimentary antigen on a pathogen, which activates the B-cell, causing it to undergo clonal expansion (divide)
What is clonal expansion?
mass rapid increase in antibody-producing B cells by mitosis
What is active immunity?
immunity obtained when your immune system makes its own antibodies after being stimulated by an anitgen
What is passive immunity?
immunity obtained from being given antibodies from a different organism
-body doesn’t produce the antibodies itself
Give an example of natural active immunity
when you become immune after catching a disease
Give an example of artificial active immunity
when you become immune after being given a vaccination containing a harmless form of the antigen which causes the immune system to produce antibodies
Give an example of natural passive immunity
a baby becoming immune by being given antibodies from its mothers blood (through the placenta) or from colostrum (mother’s milk)
Give an example of artificial passive immunity
having an injection of antibodies
-antibodies produced in one individual are extracted and injected into another individual
What is an autoimmune disease?
a disease caused by an organism’s immune system being unable to recognise self antigens (treats them as foreign antigens) so acts against its own cells and destroys healthy tissues in the body
Name some examples of autoimmune diseases
- arthritis (immune system attacks cells in connective tissues, can affect skin, joints and organs)
- lupus (immune system attacks cells in joints)
What is a vaccine?
a safe form of an antigen injected into the blood stream to trigger the primary immunity response to the immune system produces antibodies specific to the antigens and memory cells so if you come into contact with the antigen again, the secondary immune response recognises it and destroys the pathogen
What are routine vaccines?
injections offered to everybody
eg. MMR vaccine and Meningitis C vaccine
What is a pandemic?
when a communicable disease spreads rapidly across several countries or continents
What is an epidemic?
when a communicable disease spreads rapidly to a lot of people in a local/national area
Why do vaccines sometimes need to be changed?
new strains of pathogens are produced (from mutations and natural selection) which have different antigens to previous strains, meaning new vaccines need to be made containing the correct antigens
What are common sources of medicine?
-microorganisms and plants
-designing drugs using computer programmes
-using computer libraries of chemicals
future -personalised medicines
-synthetic biology
What do antibiotics do?
damage and destroy bacterial cells by inhibiting their metabolism
-are selectively toxic (only destroy bacteria, not body cells)
What is antibiotic resistance?
when bacteria becomes resistant to antibiotics
-mutations cause bacteria to be resistant and this is passed on via natural selection (resistant allele passed onto offspring)
Name some examples of resistant bacteria
MRSA -resistant to meticillin
C.difficile
What do parasites do?
- live on host cell at expense of host (harms host)
- feeds on host to gain nutrition
