[FMS] CBS - cell death Flashcards
difference between apoptosis and necrosis
Apoptosis = regulated cell death (RCD) / Programmed Cell Death (PCD) : cell dies in a controlled way
Necrosis = Accidental cell death (ACD)
in apoptosis are the triggers intrinsic, extrinsic?
both
in apoptosis are the contents of the cell released?
no
in apoptosis is there an inflammatory response?
no
in necrosis in what 2 ways do the cells die
- Cells die due to lack of ATP (hypoxia or ischemia)
- Cell death due to physical damage – injury
in necrosis are the contents of the cell released?
yes, into extracellular space
in necrosis is there an inflammatory response?
yes
2 roles of apoptosis
- remodelling/development
- removing damaged cells
what happens when skin cells are exposed to UVB, how is apoptosis involved?
- UVB induces chemical bonds between adjacent thymines = thymine dimers
- dimers disrupt DNA structure and interfere with accurate replication = mutations
- repaired by Nucleotide Excision Repair (NER) Pathway
- excessive damage = removed via apoptosis preventing cancer development
- skin keratinocytes form “sunburn cells” and undergo apoptosis in response to excessive exposure to sunlight
outline the 7 morphological changes during apoptosis
- smaller cell
- cytoskeleton collapse
- nuclear envelope disassembles
- chromatin condense and fragmented
- cell surface bulges (blebs)
- cells break up into membrane bound apoptotic bodies
- bodies engulfed and destroyed by phagocytosis - macrophages
- rapid process
whats the intracellular mediator of apoptosis/ what triggers the intracellular events of apoptosis
caspases
what family do caspases come from?
proteases
how are caspases synthesised
Caspases synthesised as inactive precursors that
are activated by cleavage during apoptosis
2 types of caspases
initiator caspases
executor caspases
where are initiator caspases found? what is its apoptotic trigger?
found inactive as monomers in cytosol
apoptotic trigger = dimerisation, activation, cleavage
how are executor caspases activated?
- Initiator caspases cleave and activate executor
caspases - Activated executor caspases activate by
cleavage all the changes in cell biology
observed in apoptosis
whats the function of a caspase?
to increase phosphatidylserine in the outer membrane layer
what is CAD?
- a specific endonuclease
how is a ladder of fragments formed in DNA fragmentation?
DNA fragmentation into discrete chunks occurs due
to activation of CAD
Executioner caspases degrades iCAD – a specific
inhibitor of CAD
DNA is cleaved in the regions between
nucleosomes that result in a ladder of
fragments
what is the extrinsic pathway for apoptosis?
what is the intrinsic (mitochondrial) pathway to trigger apoptosis?
what activates the caspase cascade in cytotoxic t-cells in the extrinsic pathway for apoptosis?
binding of FAS ligand to FAS receptor
death receptors are part of which family of receptors
TNF (tumor necrosis factor) family of receptors
when fas ligand binds to fas receptor what happens
activates initiator caspases and forms the death-inducing signalling complex (DISC)
