Regulation of the cell cycle- lecture #15

Question 1

molecular control systems exist, what are the 2 things that are critical to normal cell development?

Answer 1

timing and the rate of cell division

Question 2

frequency of cell division varies depending on what?

Answer 2

the cell type

Question 3

what two cells dont divide at all?

Answer 3

muscle and nerve cells

Question 4

what do molecular regulatory mechanisms do?

Answer 4

cause differences in division

Question 5

why do we need regulation in cells?

Answer 5

to ensure we’re making just whats required

Question 6

what are signaling molecules?

Answer 6

protein

Question 7

where are signaling molecules located?

Answer 7

in the cytoplasm

Question 8

what are signaling molecules important for?

Answer 8

cell cycle control systems

Question 9

what do signaling molecules do?

Answer 9

communicate to give an order to happen, tells the cell what to do

Question 10

cell division is regulated at certain checkpoints that are located where?

Answer 10

internal and external

Question 11

what kind of signals do checkpoints give? what do checkpoints do?

Answer 11

stop and go signals
regulate the cell cycle

Question 12

at what points do checkpoints occur?

Answer 12

G1, S and G2 phases

Question 13

what checkpoint/ phase is the most important?

Answer 13

G1

Question 14

if the cell passes checkpoint G1, what happens?

Answer 14

the cell will move on and be committed to divide
like when you go on an airplane, once you reach a certain speed you cant stop

Question 15

what happens if the cell does not pass checkpoint G1?

Answer 15

it will enter into G0 (G not) and not go on to divide

Question 16

do cells stay in G0 for life?

Answer 16

some cells do
other cells are pulled out of G0

Question 17

when a cell is pulled out of G0 what factor influences it?

Answer 17

based on external cues and enter into normal division

Question 18

what are the two types of kinases?

Answer 18

cyclin dependent and cyclin independent

Question 19

what does protein kinases do?

Answer 19

activate and deactivate protein via phosphorylation

Question 20

what phases is protein kinases important for?

Answer 20

G1 and G2 phases

Question 21

is CDK always present?

Answer 21

yes, when active or inactive

Question 22

in order for CDK to gain activity what does it have to attach to?

Answer 22

cyclin

Question 23

activity will increase or decrease based on what?

Answer 23

the presence of the cyclin partner

Question 24

what does MPF do?

Answer 24

triggers the movement of the cell past G2 in mitosis

Question 25

what is the charger to MPF?

Answer 25

when cyclin and Kinase are together

Question 26

when does MPF decrease?

Answer 26

when cyclin decreases

Question 27

when does cyclin increase? what happens due to this increase?

Answer 27

cyclin increases in G2 and binds to MPF

Question 28

after cyclin binds to MPF, what does MPF do?

Answer 28

phosphorylates and activates proteins and other kinases (MPF also deactivates)

Question 29

when MPF activates proteins and kinases what does this initiate?

Answer 29

mitosis

Question 30

what happens when MPF initiates mitosis?

Answer 30

proteins that cause the fragmentation of the nucleus arrive and are activated assists with chromosome condensation assists with spindle formation

Question 31

during anaphase what does MPF do?

Answer 31

switches itself off

Question 32

when MPF switches itself off what does this activate?

Answer 32

a process that causes destruction of its own cyclin

Question 33

what else occurs to MPF when it switches itself off?

Answer 33

inactivates MPF

Question 34

when the MPF inactivates what happens to the CDK?

Answer 34

still kept at high concentration

Question 35

what happens if we dont shut this process down?

Answer 35

cancer

Question 36

if division needs to keep happening what will continue to enter the cycle?

Answer 36

cyclin

Question 37

in order to completely deactivate this reaction what needs to happen?

Answer 37

have to break apart cyclin to deactivate reaction

Question 38

what signals are used as stop/go signs at the checkpoints of the cell cycle?

Answer 38

internal and external

Question 39

in order for the cycle to move forward how must sister chromatids be aligned during anaphase?

Answer 39

aligned down the metaphase plate

Question 40

when sister chromatids are properly aligned what is activated?

Answer 40

regulatory complex

Question 41

what does the regulatory complex activate?

Answer 41

separase

Question 42

what does separase do?

Answer 42

cleaves cohesins between sister chromatids (cuts them apart)

Question 43

what does separase protect?

Answer 43

the chromosomal content of daughter cells

Question 44

what 2 factors influence cell division?

Answer 44

physical and chemical

Question 45

what will stop cell division?

Answer 45

lack of an essential nutrient (despite all other conditions favorable)

Question 46

what are growth factors made of?

Answer 46

proteins

Question 47

what do growth factors do?

Answer 47

released by cells in order to stimulate other cells to divide

Question 48

how many known types of grow factors are there?

Answer 48

>50

Question 49

what is the process of the platelet derived growth factor (PDFG)?

Answer 49

tissue blended up results in free fibroblasts cells are transferred to culture vessels (one with PDFG, one without) plate with PDFG are given the signal to divide

Question 50

why do only certain cells listen to this signal of PDFG?

Answer 50

or else everything in your body would start dividing

Question 51

the binding of PDFG to the receptor causes the cell to pass the G1 checkpoint and divide, why does this occur in the body?

Answer 51

to allow wound healing

Question 52

what is density dependent inhibition?

Answer 52

crowded cells will stop dividing if theres too much density

Question 53

in density dependent inhibition what is another factor that stops the cell cycle

Answer 53

cell surface protein binds to the counterpart on the adjacent cell and inhibits the growth of both cells

Question 54

what is anchorage dependence?

Answer 54

cell division will not occur unless cells are attached to a solid support

Question 55

what is an example of an anchor for anchorage dependence?

Answer 55

extracellular matrix or bottom of a container

Question 56

what is anchorage dependence controlled by?

Answer 56

plasma membrane proteins and the linked cytoskeleton

Question 57

what do cancer cells not exhibit?

Answer 57

density dependence inhibition or anchorage dependence

Question 58

what do cancer cells primarily do?

Answer 58

ignore normal signals divide excessively (invading healthy tissues)

Question 59

in the absence of growth factors what happens to cancer cells?

Answer 59

continue to divide may produce their own growth factors

Question 60

what are atypical checkpoints?

Answer 60

when cancer cells stop dividing at random points

Question 61

how are cancer cells immortal?

Answer 61

with unlimited nutrients they will divide indefinitely

Question 62

normal cells divide how many times before aging and dying?

Answer 62

20-50 times

Question 63

how does a mass of abnormal cells occur (tumor)?

Answer 63

if the immune system doesnt recognize the abnormal cell it will proliferate becoming a tumor

Question 64

if a tumor remains in one spot what is it considered?

Answer 64

benign

Question 65

if the tumor undergoes required changes and moves to another site what is it considered?

Answer 65

malignant (metastatic cancer)

Question 66

what causes cancer cells to be so successful?

Answer 66

collection of mutations

Question 67

chromosomes have what chromosome number?

Answer 67

unusual chromosome number

Question 68

what do cancer cells loose their ability to do because of this unusual chromosome number?

Answer 68

attach to surrounding cells and the extracellular matrix

Question 69

cancer cells may produce what that allow blood vessels to grow inward?

Answer 69

signaling molecules

Question 70

what can cancer cells be treated with?

Answer 70

high energy radiation and chemotherapy

Question 71

what does chemotherapy do?

Answer 71

selective toxicity drugs are administered into the blood that target the cell cycle in actively dividing cells

Question 72

what are the side effects of chemotherapy?

Answer 72

healthy dividing cells are also targeted, making you weak

Question 73

why is high energy radiation more specific to cancer cells?

Answer 73

because they loose their ability to repair DNA damage

Question 74

what toxicity is less extreme? high energy radiation or chemotherapy?

Answer 74

high energy radiation you get burns but toxicity isn't as extreme, you can play hockey the next day1