Apoptosis Flashcards
Is apoptosis or necrosis the most common form of cell death?
Apoptosis
True or False:
In apoptosis, cell contents spill out; in necrosis, cells shrink and condense.
False - apoptosis, cells shrink and condense (contents never leak out); necrosis, cell contents spill out.
Give an example of apoptosis being important in development of mice and humans.
Apoptosis (cell death) sculpts hands and feet during embryonic development. Thus, keeping hands and feet from being webbed.
List the phenotype of apoptosis (characteristics).
- overall shrinkage in volume of cell and its nucleus.
- loss of adhesion to neighboring cells.
- formation of bless on surface.
- DNA fragmentation
- cytoskeleton collapses
- nuclear envelope disassembles.
- rapid engulfment of dying cell by phagocytosis (macrophages).
What type of certain cells is programmed cell death important for?
- abnormal cells
- non-functional cells
- potentially dangerous cells
- eliminating lymphocytes after destroying and ingesting microbes
- keep organs the correct size (liver)
- DNA damaged cells are destroyed if bad enough damage
When running an agarose gel to look at the characteristics of apoptotic cells, where does the endonuclease the DNA resulting in a ladder of fragments in distinctive sizes?
Endonuclease cleaves in linker regions of nucleosomes.
What is the key event to initiate apoptosis?
Activation of caspases.
Caspase = Cysteine Aspartyl specific proteASE
What amino acid is the active site in caspases?
Cysteine in active site.
Where does caspase cleave target proteins?
Caspase targets proteins and cleaves them in their sequence where an aspartic amino acid residue occurs.
What inactive precursor is caspases synthesized first as?
Procaspase
To activate procaspase, what is it cleaved to form?
Procaspases cleaved at specific sites to form a large and small subunit which form a heterodimer - caspases activates procaspase.
What are the two major classes of caspases?
- Initiator caspase
- executioner caspase
What do initiator caspases do?
Initiate apoptosis (including caspase-8 and caspase-9)
What do executioner caspases do?
Destroys actual targets - executes apoptosis (includes caspase-3).
True or False:
The caspase cascade is irreversible.
True
What do activated caspases do?
- cleaves downstream proteins
- cleaves inactive endonuclease
- targets cytoskeleton
- attacks cells adhesion proteins (cells roll up in ball)
True or False:
Executioner caspases auto-activates itself.
False - Initiator caspase auto-activates itself.
executioner caspases cleaves cellular targets
What are the two apoptotic pathways?
- internal pathway
- external pathway
Give an example of an internal stimuli that activates the internal apoptotic pathway.
Abnormalities in DNA.
Give an example of an external stimuli that activates the external apoptotic pathway.
Removal of survival factors and proteins of tumor necrosis factor family.