Lecture 31

Question 1

Is the cell cycle duration the same for all cells

Answer 1

no, varies with the cell type, not a clock but just a pattern or series

Question 2

Fastest cell cycles examples and time

Answer 2

(hours/ day)
red blood cell precursors
spermatocytes
epithelial cell progenitors

Question 3

Slow cycles examples and time

Answer 3

(days/ weeks)
liver cells
immune memory cells
glandular cells

Question 4

Cells that don’t divide at all examples

Answer 4

nerves
muscle
fat cells (adipocytes)

Question 5

Lack of nutrients or proper signals from tissues may induce what during the cell cycle

Answer 5

may induce arrest in Go (taking an indefinite break from the cycle)

Question 6

Typically, most cells spend the most time in what part of the cell cycle

Answer 6

G1

Question 7

What happens during G1 in cell cycle

Answer 7

cells carry out specific jobs

Question 8

When do cells leave G1 in the cell cycle

Answer 8

when they get a signal to divide

Question 9

what is the “job” of stem cells

Answer 9

to divide

Question 10

Main cycle checkpoints/ restriction points

Answer 10

G1 to S
G2 to M
Metaphase to Anaphase

Question 11

Once a cell passes a checkpoint, can it turn back?

Answer 11

No!

Question 12

Levels of specific proteins determines what

Answer 12

the cycle phase

Question 13

What is Heterokaryon

Answer 13

fused cell with two nuclei, all the protein contents of cells are mixes so resulting phenotype gives insight to cell control mechanisms

Question 14

How do we know when the activity of mitosis promoting factor (MPF) peaks?

Answer 14

observing the cyclin proteins, which show gradual build-up and rapid decline over cell cycle

Question 15

Where does the mitosis-promoting factor (MPF) peak?

Answer 15

During mitosis

Question 16

Cyclin expression is controlled by

Answer 16

growth factors

Question 17

What stimulates cells to divide

Answer 17

epidermal growth factor (EGF)

Question 18

Steps of stimulating a cell to divide

Answer 18

1. epidermal growth factor (EGF) is received by special GF receptors on the cell surface that transduce the signal into the cytosol side
2. EGF receptors signals are passed on to Ras protein, which binds GTP and communicates with a downstream chain of proteins
3. the result is increased expression of G1-S cyclins

Question 19

Cyclins work by

Answer 19

guiding other proteins

Question 20

What proteins do cyclins bind to

Answer 20

cyclin-dependent kinase (CDK) proteins, directing activity to different targets controlling gene expression

Question 21

What is apoptosis

Answer 21

programmed cell death, normal part of tissue development and maintenance

Question 22

Why do cells program apoptosis

Answer 22

old/damaged cells need to be carefully recycled because they cant just burst bc it may release harmful signals

Question 23

How long does apoptosis take

Answer 23

less than 1 hour

Question 24

Steps of apoptosis

Answer 24

1. chromosomes condense and cytoplasm sinks
2. nucleus and cytoplasm become fragmented and DNA is digested, and the cell extends
3. the remnants of the dead cell are ingested by phagocytic cells

Question 25

Caspases are

Answer 25

enzymes that cleave other proteins for apoptosis

Question 26

Apoptotic pathways may be stimulated by

Answer 26

immune cell signals (T lymphocytes), nutrient deficiency, and DNA damage