LOOs 14 Flashcards
What are the three different classes of extracellular signaling molecules? What do they do?
1) Mitogens - stimulate cell division
2) Growth factors - stimulate cell growth
3) Survival factors - promotes cell survival by suppressing programmed cell death.
How do mitogens stimulate the cell cycle?
by triggering a wave of G1/S-Cdk activity.
When does the cell sense DNA damage?
Cells can readily detect DNA damage and arrest the cell cycle at Start or
G2/M transition.
What is the difference between cell division and cell growth?
Cell growth is an increase in cell mass. Cell division is creating 2 daughter cells from 1 parent cell
How does DNA damage block cell division?
Kinase activates and phosphorylates p53 protein. p53 protein targets p21 gene that produces CKIs (Cdk inhibitors). CKI binds allosterically to cyclin-Cdk complex inactivating it.
When do cells coordinate cell division and cell growth?
for proliferating cells
When do cells not coordinate cell division and cell growth?
cells that are terminally differentiated
What are the two types of cell death? How are the two types of cell death different?
apoptosis - programmed cell death
necrosis - death in response to an acute injury
difference - necrosis is messy, cell is lysed, apoptosis has clear pathway
How do caspases function?
Caspases are intracellular proteases that cleave specific proteins to assist in apoptosis.
What is the difference between an initiator caspase and an executioner caspase?
Initiator caspases - begin apoptotic program. they will activate executioner caspases
executioner caspases - orchestrate the apoptosis program by cleaving different cell proteins
What are some known cellular targets of executioner caspases?
1) executioner Caspase-6 targets nuclear lamins which results in the irreversible breakdown of nuclear lamina
2) executioner caspase-3 targets iCAD which will cleave free DNA between nucleosomes
What is the extrinsic pathway of apoptosis?
when a signal from outside the cell binds to cell-surface death receptors to trigger the extrinsic pathway of apoptosis
How does FLIP set an inhibitory threshold?
through activated caspase-8
What is the intrinsic pathway of apoptosis?
when an initiation of apoptosis signal occurs inside the cell. It depends on proteins released from the mitochondria specifically cytochrome C is the protein and it binds to adaptor protein along with inactive caspase-9 forming active apoptosome that realeasescative caspase 9
What cellular mechanisms regulate the intrinsic pathway of apoptosis?
1) MOMP (mitochondrial outer membrane proteins) allow cytochrome c to exit intramembrane space to cytosol
2) pro-apoptotic Bcl2 proteins (Bac and Bax in the cytosol) are oligomerized by a signal in outer mitochondrial membrane, leading to a permeable pore that allows cytochrome c to leave
