3-cell cycle Flashcards
4 main extracellular signals that regulate cell survival, growth and division
- survival factors
- growth factors
- mitogens
- growth inhibitory signals
survival factors suppress
apoptosis
GFs stimulate
an increase in the size of a cell
mitogens stimulate
cell division
growth inhibitory signals promote
differentiation and inhibit cell growth and division
upon entering G1, daughter cells can
leave the cell cycle or continue in proliferative state
what happens during S
entire genome is replicated
the decision whether to divide or go in G0 occurs during
G1 phase
during the question period in G1, cells respond to
mitogenic signals and growth inhibitory signals
After R, they no longer respond to
external signals
once a cell passes through R, it is committed to
going through the entire cell cycle
central components of the cell cycle control system are
CDKS
at each stage of the cycle
a specific CDK- cyclin phosphorylates the proteins to execute the next step
CDKS are _____ present
always
cyclin levels _____
fluctuate
cyclin D is important because it is synthesized in response to
external growth promoting signals
cyclin D- CDK 4/6 complex phosphorylates substrates that allow the cell to pass through
G1 and pass R
The cyclin D-CDK 4/6 complex promotes progression through the restriction point by
phosphorylating Rb
without mitogenic signals, Rb forms a complex with
E2F transcription factors
when bound to Rb, E2F TFs are unable to stimulate
gene transcription
hypophosphorylation of Rb causes
Rb to let go of E2F which can now stimulate gene transcription
