Lecture 31 Flashcards
Is the cell cycle duration the same for all cells
no, varies with the cell type, not a clock but just a pattern or series
Fastest cell cycles examples and time
(hours/ day)
red blood cell precursors
spermatocytes
epithelial cell progenitors
Slow cycles examples and time
(days/ weeks)
liver cells
immune memory cells
glandular cells
Cells that don’t divide at all examples
nerves
muscle
fat cells (adipocytes)
Lack of nutrients or proper signals from tissues may induce what during the cell cycle
may induce arrest in Go (taking an indefinite break from the cycle)
Typically, most cells spend the most time in what part of the cell cycle
G1
What happens during G1 in cell cycle
cells carry out specific jobs
When do cells leave G1 in the cell cycle
when they get a signal to divide
what is the “job” of stem cells
to divide
Main cycle checkpoints/ restriction points
G1 to S
G2 to M
Metaphase to Anaphase
Once a cell passes a checkpoint, can it turn back?
No!
Levels of specific proteins determines what
the cycle phase
What is Heterokaryon
fused cell with two nuclei, all the protein contents of cells are mixes so resulting phenotype gives insight to cell control mechanisms
How do we know when the activity of mitosis promoting factor (MPF) peaks?
observing the cyclin proteins, which show gradual build-up and rapid decline over cell cycle
Where does the mitosis-promoting factor (MPF) peak?
During mitosis
Cyclin expression is controlled by
growth factors
What stimulates cells to divide
epidermal growth factor (EGF)
Steps of stimulating a cell to divide
- epidermal growth factor (EGF) is received by special GF receptors on the cell surface that transduce the signal into the cytosol side
- EGF receptors signals are passed on to Ras protein, which binds GTP and communicates with a downstream chain of proteins
- the result is increased expression of G1-S cyclins
Cyclins work by
guiding other proteins
What proteins do cyclins bind to
cyclin-dependent kinase (CDK) proteins, directing activity to different targets controlling gene expression
What is apoptosis
programmed cell death, normal part of tissue development and maintenance
Why do cells program apoptosis
old/damaged cells need to be carefully recycled because they cant just burst bc it may release harmful signals
How long does apoptosis take
less than 1 hour
Steps of apoptosis
- chromosomes condense and cytoplasm sinks
- nucleus and cytoplasm become fragmented and DNA is digested, and the cell extends
- the remnants of the dead cell are ingested by phagocytic cells
