Apoptosis (6.3) Flashcards
Describe what the growth and development of a multicellular organism requires
Careful regulation of cell division, differentiation and cell death
State what process regulates cell division, differentiation and cell death
Cellular signalling
Describe apoptosis
Regulated and programmed cell death
State what billions of cells in your body die of every hour
Apoptosis
State what ‘self-destruction’ enables a multicellular organism to do
Regulate cell numbers
State what molecules apoptosis involves
Signalling molecules
State what type of response apoptosis is considered
Receptor-mediated
State 3 common occurrences that promote apoptosis
- cell ageing
- cell obsolescence
- damaged DNA
Describe cell obsolescence as a factor promoting apoptosis
Lack of requirement for the cell
Describe caspases
Group of enzymes involve in protein and DNA cleavage
State where caspases are produced
Within the cell
State how caspases are stored
Inactive precursors
State what group of enzymes are responsible for apoptosis
Caspases
Describe the path of a signalling molecule in terms of caspase activation
- signalling molecule produced
- binds to receptor
- binding activates caspase
- caspase stimulates other caspases
Describe what caspase activation can be considered in apoptosis
Cascade
Provide 1 example of a caspase
- caspase-3
State what caspase-3 causes during the process of apoptosis
Fragmentation of actin filament and inactivation of DNA repair
State 6 roles of caspases in apoptosis
- DNA cleavage
- nuclear protein degradation
- nuclear membrane cleavage
- cytoskeleton dismantling
- protein breakdown
- organelle breakdown
Describe bleb
Protrusion or bulge of the cell membrane
State whether or not apoptosis can be stopped or reversed
Apoptosis cannot be stopped or reversed once triggered
State the 7 major steps of apoptosis
- cell separation
- cytoskeleton collapse
- cell shrinkage
- organelle breakdown
- bleb formation
- apoptotic bodies budding
- phagocytosis of apoptotic bodies
Describe what the budding of apoptotic bodies prevents
Toxic or immunogenic substances from leaking as a result of phagocytosis
Describe what cells are responsible for the phagocytosis of apoptotic bodies
Specialised phagocytes - usually macrophages
Describe an inflammatory response. Provide 2 examples of what might trigger it.
Protective response triggered by damaged tissue or invading pathogens
State what phagocytosis of apoptotic bodies prevents
Triggering of an inflammatory response
State the 2 pathways of apoptosis
- intrinsic
2. extrinsic
State what determines which apoptotic pathway is taken
Signal source (inside or outside of the cell)
Provide another term used to describe the intrinsic pathway of apoptosis
Mitochondrial pathway
Provide another term used to describe the extrinsic pathway of apoptosis
Death receptor pathway
State 4 factors which may trigger the activation of the mitochondrial pathway of apoptosis
- damage via radiation
- viral infection
- toxins
- damaged DNA
State from which part of the cell a signal must originate for the mitochondrial pathway of apoptosis to be triggered
Inside the cell
State from which part of the cell a signal must originate for the death receptor pathway of apoptosis to be triggered
Outside the cell
State what the mitochondrial apoptosis signalling pathway is regulated by
Proteins
Describe the role of Bcl-2 in regulating the mitochondrial apoptotic pathway
(pro-) promote or (anti-) inhibit apoptosis
State what Bcl-2 proteins do following stress or cellular damage
Proteins relocate from the cytoplasm to the mitochondrial surface causing pore formation
State what substance is released from the mitochondria into the cytoplasm as a result of the relocation of the Bcl-2 proteins
Cytochrome c into the cytoplasm
State in which organelle cytochrome c is located
Mitochondria
State what cytochrome c forms with a protein called Apaf-1 in the cytosol
Apoptosome
State what Apaf-1 represents
Apoptotic protease-activating factor
Describe apoptosome
Large protein formed as a result of apoptosis
State what apoptosome activates
Cascade of caspases
Describe death receptors
Specific receptors on the outer surface of cells that will bind to cytokines
State what death receptors are specific to
Cytokine signalling moleulces
State what proteins death receptors are classified as
Transmembrane proteins
State where death receptors are located on a cell
Plasma membrane
State what occurs when a signalling molecule binds to a death receptor
Signal transduction initiates a cascade that lead to apoptosis
State what too much cell death may result in
Loss of vital tissue
State what too little cell death may result in
Tumor formation/cancer
Provide 3 examples of condition triggered by excessive apoptosis
- Alzheimer’s disease
- Parkinson’s disease
- Motor neuron disease
Provide 1 example of a condition triggered by inhibited apoptosis
Syndactyly
Describe syndactyly
Failure of sin between digits to be removed during embryonic development
Describe Alzheimer’s disease
Neurodegenerative disease that results in the shrinking of the brain due to a loss of neurons
Describe cancer
Group of diseases that commonly involve unregulated and abnormal cell growth/division
