Life And Death If Cells Flashcards
What are post mitotoc cells
Cells thst never divide
What are senescent cells
Cells thst lose ability to divide due to ageing
Phases of cell cycle
G1
S
G2
M phase
G1 phase
Cell undergoes more protein synthesis- lots of gene transcription and synthesis of RNA
cells duplicate organelles
cell is highly active and needs energy
S phase
Duplicate DNA
Extra copy of chromosome is made
Two copies are joined at centromere
G2 phase
Rapid period of cell growth as cell readies itself for mitosis
Cell checks its DNA to make sure that it is correctly copied
M phase
Fastest stage
Nuclear envelope break down
Mititic spindle forms and chromosomes are separated
Cell splits ( cytokinesis)
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
What is role of kinetichore
Structure that attaches chromosomes to microtubules
Leading to segregation of chromosomes
What is hayflivk limit
Most multicellular organisms have limited lifespan even when all nutrients are present
Lifespan around 40-60 cell division
Two types of cell death
Necrosis ( uncontrolled cell death due to disease)
Aptosis (programmed cell death)
How is aptosis triggered
Receptor mediated
Mitochondria mediated - activated by mitochondria by cell stresses like free radical damage DNA damage viral infection
Importance of apoptosis
Embryo development- sculpt tissue
Immune System- destroy virus infected cells and self reacting immune cells
Homeostasis- counter Balance cell division and remove old damage
Cancer - cancer drugs worl by inducing apoptosis
How do capsases worl
They r 12 proteases that exist as inactive pronenzymes. After activation by cleavage they activate other caspases
Two types of apoptosis caspases
Initiator caspases activate other caspases
Effector /executioner caspases break down cellular components
How do receptor mediated apoptosis work
Death inducing ligand binds to death receptor, change in shape of receptor causes Platform to be created which allows for removal of cap on the procaspase which is initiator caspase, which removes cap on executioner caspase which kills the cell.
How does mitchomdria mediated apoptosis worl
Pores form In outer mitochondrial membrane allowing release of cytochrome C into cytosol. Cytochrome C binds to other cystolic proteins to form a multi protein complex called apoptosome which acts as a platform for initiator caspase to get activated and therefore become active caspase
Where is Cytochrome C located
Inner mitochondrial membrane and essential part of electron transport chain
What is apoptosome
Multi protein complex of Apaf-1 ,cytochrome C, pro caspase 9 and ATP
What controls release of cytochrome c from mitochondria
Proteins called a Bcl-2 which detect stress
How do pro apoptotic members of bcl 2 family work to release cytochrome C
Insert themselves into mitochondrial surface and promote formation of large pores in outer membrane that leads to cytochrome c
Where do anti apoptotic members of bcl 2 exist
Mitochondrial outer membrane and act to block action of pro apoptotic
