U1AOS1 Apoptosis and Stem Cells Flashcards
Necrosis
Cell death where the cell has been badly damaged due to external forces. Necrosis is uncontrolled.
Process of necrosis
The cell swells and ruptured, spilling its contents into the internal environment, often causing swelling.
Apoptosis
Programmed cell death that allows for the removal of cells without the contents spilling.
Two apoptotic pathways
- Intrinsic (mitochondrial) pathway
- Extrinsic (death ligand) pathway
Purpose of apoptosis
- Cells which are damaged or defective must be eliminated
- To sculpt the body from tissues during fetal development
Extrinsic pathway
Secretion of a death ligand such a FasL from natural killer (NK) or cytotoxic T (Tc), which binds to FasR due to complementary shape and charge
Intrinsic pathway
Molecules escape damaged mitochondria, bind to intracellular receptors, ending in Caspase 3 which cuts up the cytoskeleton
Process of apoptosis
- Caspase 3 cuts up cytoskeleton
- Cell shrinkage
- Blebs form containing organelles
- Chromatin in the nucleus condenses
- Blebs all split apart
After apoptosis
Cell debris is engulfed by phagocytes, a number of white blood cells specialised in engulfing foreign matter.
Cancer cells
Cells that have become unspecialised, and which divide and grow rapidly in an uncontrolled manner forming a tumour.
What is a stem cell?
A cell that is undifferentiated and has the ability to divide by mitosis to give rise to cells that can differentiate into different cell types.
Differentiation
Specialisation of a cell for a particular function in the body by regulation of the expression of its genes
Two types of stem cells
Totipotent and pluripotent
Totipotent
A cell with potential to differentiate into either and embryonic stem cell of an extra embryonic cell (such as placenta)
Pluripotent
A cell with the potential to differentiate into an embryonic stem cell if one of the three germ layers
