c3.2 defence against disease Flashcards
pathogen
microscopic entities that causes disease within their hosts
virus eg
covid-19
bacteria eg
e coli
fungi eg
yeast
protists
malaria
physical barriers against pathogens [2]
- mucus membranes
- skin
why mucus membranes can defend against pathogens [3]
- sticky- traps pathogen
- pH not favourable
- natural organisms- competitive exclusion by non-harmful microbes
lysozyme
enzymes that breaks down pathogens
what makes mucus
goblet cells
what moves mucus
ciliated cells
why skin can defend against pathogens [5]
- continuous
- many layers
- dry
- pH- not favourable to pathogens
- natural organisms- competitive exclusion by non-harmful microbes
metabolic pathway eg
blood clotting
mechanism of blood clotting
- clotting factors: thrombin
- fibrinogen (soluble) → fibrin (fibrous)
- captures erythrocytes
- clot
2 types of immune system
- innate immune system
- adaptive immune system
innate immune system
- doesnt change
- phagocyte
phagocyte
detect anything that might have a foreign antigen
phagocytosis
engulfs pathogens then lysozymes in their lysosomes to digest them
adaptive immune system
changes overtime depending on the individuals history of exposure to various antigens
identify lymphocyte
circle with circle inside
identify phagocyte
has ‘c’ shape inside it
mechanism of HIV
kill t helper cells → weaken immune system significantly because macrophages are too slow and cant find the pathogen
why do memory cells retain the memory
dont die
how do memory cells recognise pathogens
bind to receptor, works if the pathogen is slightly different as long as they can still bind
amoeboid movement
phagocytes use pseudopods to crawl and chase the pathogen
antigen
presented to t helper cells and the b cells (nymphocytes)
t cells
find the right b cells and release cytokines
how do t cells work
- divide into plasma cells to release antibodies
- small percentage turn into memory cells
how HIV works
infects t-helper cells and other lymphocytes to cause acquired immunodeficiency syndrome (AIDS)
what does retrovirus contain
rna
causes of HIV [5]
- bodily fluids form an infected to uninfected person
- sex without a condom
- sharing hypodermic needles
- transfusion of infected blood
- childbirth- virus can get through placenta + lots of blood during childbirth
how hiv turn into aids
- takes time for t-cell count to decrease
1. t-helper cells gets attacked and starts to die
2. if t-helper cell count too low then AIDS
how less t-helper cells lead to lowered immunity
antibodies are unable to be produced → lowered immunity
why aids causes people to die
body becomes susceptible to opportunistic infections
treatment of hiv
group of antiretroviral drugs- prevents damage to immune system
how antibiotics work [3]
- block the process of bacteria building a cell wall by linking molecules together
- bacteria can burst easier
- affect ribosomes (cell’s protein-building machines) so prevent them from building proteins. proteins do all the cell’s work so a bacterium that cant build proteins cant survive
- virus dont have ribosomes, rely on their host’s ribosomes
- causes dna strands to break and prevent the breaks from being repaired when bacteria begins to copy their dna. without intact dna, bacteria cant live or reproduce
why antibiotics dont work against viruses
Viruses do not possess a metabolism (they are not alive) bc they dont have their own metabolic reactions and instead take over the cellular machinery of infected host cells
how to treat viruses
Antiviral treatments target features specific to viruses (e.g. viral enzymes like reverse transcriptase or components of the capsid)
how do bacteria become drug resistant
can pass resistant gene through plasmids
mrsa
- bacteria- staphylococcus aureus
- og- mrsa
- variation- mssa
- result: mssa is killed, mrsa survives, nrsa reproduces so resistant gene proliferates → mrsa population increases → mrsa is a dominant strain → methycillin is no longer effective against infection
what do vaccines contain
antigens (weakened/killed pathogens) or nucleic acids (dna/rna)
why nucleic acids vers of vaccines are better
faster bc less trials needed
antigens in vaccines
sequences that code for the antigens without causing the disease
2nd response after the vaccination
create more antibodies in a shorter amount of time
zoonoses
infectious disease that can transfer from other species to humans