Apoptosis and Necrosis Flashcards
Define multiplicative growth
Increase in cell numbers by mitotic cell division
Define auxetic growth
increased size of individual cells
Where is auxetic growth seen
Skeletal muscle
Where is combined patterns of multipleand auxetic growth
Embryological development
Define differentiation
Process where a cell develops a specialised function
How does differentiation take place
Expression and repression of specific genes and gene products to produce a a cell
Define morphogenesis
Highly complex process of development of the structural shape and form of organs, limbs and facial features
What must happen for morphogenesis to take place
Primitive cell mass must undergo co-ordinated growth, differentiation and apoptosis
What are non=proliferative cells called
Quiescent
What are roles of quiescent cells
Differentiate and adopt specific phenotypes capable of carrying out specific function
Property of labile cells
- Rapid turnover
- short lifespan
Property of stable cells
Good regenerative ability but low turnover rate
Problem with pancreatitis
Excessive enzyme production - The pancreas essentially eats itself.
What is caseous necrosis
TB - is a form of cell death in which the tissue maintains a cheese-like appearance.
What two stages occur during the M phase of mitotic division
Mitosis
Cytokinesis
What phase begins the cell cycle
Gap Phase 1
What two phases can daughter cells undergo after cell division is completed
Back to Gap Phase 1
OR
Gap Phase 0
What is Gap Phase 0
Cells leave the cell cycle and go into rest
What stage are cells at if they’ve differentiated
Gap Phase 0
Why do checkpoints exist during the cell cycle
- Ensure DNA has replicated fully
2. Cells do not replicate too early in the cycle
What proteins control the production and activation of enzymes and proteins involved with DNA replication (e.g. spindle formation)
Cyclin-dependant kinases (CDKs)
How do CDKs activate target proteins
Phosphorylation
What proteins regulates activity of CDKs
Cyclins
What allows transition from one phase of a cycle to the next
Rises in cyclin concentration
How is cyclin affected if DNA replication is faulty
CDK inhibitors inhibit cyclin from working
In what condition is interruption of the cell cycle vital in
Cancer
Why is anaemia, bleeding tendency and immunosuppression a side effect of cancer chemotherapy
Drugs administered inhibit other rapidly dividing cells of the body (not just cancer cells) like bone marrow and lymphoid tissues
Define apoptosis
Programmed cell death without the release of products harmful to surrounding cells
Why is a coexistence of apoptosis and mitosis in a cell population needed
Ensure continuous renewal of cells
Allows tissue to be more adaptable to environmental demands
How are products harmful to surrounding cells not released
Resultant breakdown products from inside the cell are kept in the cell membrane
Define neoplasia
Abnormal growth of tissue
How can viruses effect apoptosis
They can disable apoptosis induction in cells they infect
How is apoptosis regulated
- Inhibitors (growth factors + extracellular matrix)
How is apoptosis induced vs necrosis
- Can be physiological or pathological
2. Pathological
How many cells are effected by apoptosis vs necrosis
- Single cells
2. Cell groups
What happens to morphology of cells during apoptosis vs necrosis
- Cell shrinkage and fragmentation (dense chromatin)
2. Cell swelling + lysis
Inflammatory response in apoptosis vs necrosis
- None
2. Usual
What pathways initiate apoptosis
- Extrinsic pathway
2. Intrinsic Pathway
Describe the intrinsic pathway of apoptosis
- Bax-Bax dimers are formed which enhance apoptotic stimuli
- Tissue expansion / apoptosis triggered
Role of Bax
Determine’s susceptibility to apoptotic stimuli
What does the intrinsic pathway respond to
Stimuli such as growth factors and biochemical stress
How does DNA damage cause activation of the intrinsic pathway for apoptosis
- Leads to stabilisation of p53 gene
- Induces apoptosis by activating BCL-2 family
- Activation of caspases
What is the role of p53
Induces the cell cycle arrest and initiates DNA damage repair
How does the extrinsic pathway induce apoptosis
Ligand-Binding at death receptors on cell surface (TNFR)
- Ligand binding causes clustering of receptor molecules and initiates signal transduction cascade
- Activation of caspases
Under what conditions is the extrinsic pathway usually activated
Immune system when it wants to eliminate lymphocytes that would produce self-antigens
What is the end product of both the extrinsic and intrinsic pathway of apoptosis
Initiator caspases (caspase 8)
What does caspase 8 go on to do
Cleaves pro-caspases
Produces executioner caspases
Role of executioner caspases
Degrade many targets such as cytoskeleton and nuclear proteins
Role of caspase-3
Activates DNase which fragments DNA
Name of the process of nucleus shrinking
Pyknosis
Name of the process of fragmenting of the nucleus
Karyorrhexis
Describe the process of apoptosis after the production of executioner caspases
- Pyknosis and karyorrhexis take place
- Membrane alters but retained
- Altering causes phagocytosis
What are apoptotic bodies
Dead cells not phagocytose further
Why is there no inflammatory response to apoptotic cells
Cell membrane is intact
Name three disorders that can arise from apoptotic failure
- Cleft Palate
- Spina Bifida
- Fistula
What two features characterise necrosis
Bioenergetic failure
Loss of plasma membrane integrity
