Cell Death Flashcards
Describe the key characteristics of living cells
-fluid and ion homeostasis
Cells use energy to maintain their internal environment and water homeostasis, by active transport
-metabolic homeostasis
Proteins, membranes and organelles get degraded with use, build new proteins and organelles
How do we consider cell death
A cell that was previously healthy stops working as intended, and breaks down over time
What are the two extremes of the cell death spectrum
Necrosis and apoptosis
What are the initials temps of necrosis
-cell experiences a sudden shock
-membrane pumps stop working and/or membrane lipids lose coherence
-water starts rushing in and the cell swells (oncosis)
Outline the committed steps in necrosis
-organelles break down, releasing enzymes and other content into the cytosol
-runaway enzymes digest more cellular components
-the cell membrane lyses, releasing the cellular content to the outside- spreads digestive enzymes
Which cells do phagocytes remove
Non-inflammatory phagocytes remove apoptosis bodies (by phagocytosis)
Inflammatory phagocytes remove spilled content from necrotic cells (by pinocytosis)
Why does apoptosis occur
-detects an internal damage
-is told to do so by other cells
-lacks the right extra cellular environment
How is apoptosis mediated.
By caspases that are proteases- exist all the time in the inactive form called procaspases
-signal amplified through a proteolytic cascade: pro apoptosis signals activate the initiator caspases, which then activate the executioner caspases
Outline the initial steps of apoptosis
-caspases digest the cytoskeleton, making the cell shrink, lose shape and detach from surrounding cells and extra cellular medium
-caspase-activated DNAes (CADs) digest the DNA. Caspases digest the nuclear lamina, causing the separation of the nucleus in multiple pieces
Outline the late steps of apoptosis
-cell membrane blebs and then breaks into apoptosis bodies, organelles get partitioned between the apoptosis bodies
-macrophages are recruited to phagocytes and digest the apoptotic bodies
Outline the intrinsic pathway of apoptosis
Cellular stress disrupts the mitochondrial membrane
Cytochrome C and other mitochondrial content leaks in the cytosol
Cytochrome C activates the caspases
Outline the extrinsic pathway of apoptosis
A killer lymphocyte recognises a foreign antigen on the cell membrane
The killer lymphocyte binds to the cells death receptor, activating the receptors death domain
This causes an intracellular signalling cascade, which ultimately activates the caspases
What are survival factors
-activate a protein that stabilises the mitochondrial membrane
-activate a protein that inactivates the caspases
-induce the synthesis of a protein that stabilises the mitochondrial membrane
-induce the synthesis of a protein that inactivates the caspases
-inhibit the synthesis of caspases or other proteins-apoptotic proteins
