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Lecture 7

Biology 2382B Lecture Notes - Lecture 7: Ulna, Macrophage, Necrosis

Course Code
BIOL 2382B
Sashko Damjanovski

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= cells need to get rid of bad things - in this case, getting rid of the entire cell via
programmed cell death
NOTE: necrosis is getting rid of external damage (not normal), this is
programmed cell death (different & normal)
performed in a controlled fashion
many dangerous things inside a cell that can be dangerous if released/just
floating around
specific pathway to get rid of cells we don’t want
not a mess - very specific
ensures normal embryonic development
proper tissue homeostasis in adult animals
active cellular process that is morphologically distinct from necrosis (where
cell swell and burst)
in apoptosis, things are fragmented into little bits call ‘apoptotic
bodies’ which are then removed via phagocytic cells (like
getting rid of DNA is particularly important because it can be very
nucleus has to be fragmented in a very specific way
DNA is cut and packaged to be taken away very neatly
fragments are cut that are very manageable - you can run apoptotic
DNA on a gel without the need to cut it yourself

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C. elegans:
easy to manipulate because we know every single cell in these organisms,
very easy to keep track of
genome is very small and has been fully sequenced
1mm long
two sexes exist:
○ hermaphrodite
○ male
transparent - good for observation
noticed that same cells always die in the developmental process to
form a hermaphrodite - this suggests that programmed cell death is
looked at mutations in specific genes called ced-3, ced-4 and ced-9
(cell death abnormal genes)
observed live organisms using DIC microscopy
found that:

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mutations in ced-3 and ced-4 caused these cells not to
die in the developmental process, where they normally
would - proapoptotic
mutations in ced-9 did cause these cells to die, where
they normally would not - antiapoptotic
cells are always on the balance of proapoptotic and
antiapoptotic - all based on expression of certain genes
ced-3 is
actually an
enzyme called a caspase = a cysteine-dependant aspartate-directed
they cleave all the different components in the cell - required to
package all the stuff for disposal
since you want to be able to regulate apoptosis, and caspases are
quite dangerous - they are made in an inactive form called a
procaspases have an extra domain that needs to be removed
for caspases to be active
lots of enzymes are made this way
two types:
Initiator caspases: cleave inactive pro-forms of effector
caspases in a controlled way, thereby activating them (turns
on other caspases)
amplifying a signal
activate effector caspases
Effector (executioner caspases): cleave other proteins
substrates within the cell, to trigger the apoptotic processes
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