Ch. 18 Overview of Cell Cycle + Control System

Question 1

draw out the cell cycle and main steps

Answer 1

…

Question 2

why is a cycle for cellular division necessary

Answer 2

provides a mechanism for cellular control

Question 2

why do cells divide

Answer 2

to make copies, pass on genetic information, develop complexities in organisms (multicellular)

Question 3

what must happen to cells before they divide

Answer 3

doubling of their size (which in turn, doubles chromosomes, organelles, macromolecules, and cytosol)

Question 4

what do cell cycle times reflect

Answer 4

amount of DNA and function

Question 5

name the general phases of the cell cycle

Answer 5

interphase and M phase

Question 6

what are the steps of the cell cycle

Answer 6

G1, S, G2, mitosis, cytokinesis

Question 7

what occurs in the G1 phase

Answer 7

• period of waiting after cytoplasmic division and before next DNA replication
• checkpoint if there are enough nutrients in the external environment for the cell before replication

Question 8

what occurs in the S phase

Answer 8

DNA replication (S for synthesis)

Question 9

what occurs in the G2 phase

Answer 9

• period of waiting after DNA replication and before mitotic division
• checkpoint if all DNA has duplicated and if all DNA damage has repaired

Question 10

what is divided in mitosis; cytokinesis

Answer 10

nucleus; cytoplasm

Question 11

when is the third checkpoint in the cell cycle and what is its purpose

Answer 11

end of mitosis - considering if all chromosomes are properly attached to the mitotic spindle

Question 12

what are the ultimate goals of checkpoints in the cell cycle

Answer 12

1. sufficient nutrients
2. accurate chromosome replication
3. chromosomes are aligned to separate properly

Question 13

what is the role of cdks

Answer 13

set off series of events that initiate cell cycle (phosphorylation of different proteins)

Question 14

what does cdk stand for

Answer 14

cyclin dependent kinases

Question 15

what can help with regulating the cell cycle

Answer 15

protein kinases

Question 16

is independent cdk active or inactive; constant or non constant concentration throughout cell cycle

Answer 16

inactive; constant

Question 17

what activates cdks

Answer 17

binding of cyclin (making it a regulatory subunit)

Question 18

during the cell cycle cyclin concentrations vary or remain constant

Answer 18

vary

Question 19

there are ____ type(s) of cdks+cyclins that trigger stages of cell cycle

Answer 19

more than one

Question 20

what is M-cdk responsible for

Answer 20

regulating mitosis (M phase)

Question 21

what level of M-cyclin concentration is required for M-cdk complex entry to mitosis

Answer 21

high levels

Question 22

why is there a mismatch between cyclin levels and M-cdk

Answer 22

activation of cdks by phosphorylation and dephosphorylation causes a delay b/w M-cyclin levels and M-cdk activity

Question 23

what turns off M-cdk activity

Answer 23

• m-cyclin on m-cdk are flagged with ubiquitin to indicate that they must be degraded
• m-cyclin is taken to proteasome which destroys it
• results in inactivation of m-cdk

Question 24

draw out the activation process of M-cdk

Answer 24

main points: mitotic cdk and m-cyclin bind, inihibitory and activating kinases add phosphate groups onto complex, activating phosphatase dephosphorylates inhibitory P group to result in active m-cdk

Question 25

what types of phosphates bind to m-cdks

Answer 25

2 inhibitory and 1 activating phosphate

Question 26

what is a proteasome

Answer 26

specialized complex which can regulate degradation of cellular proteins

Question 27

what does m-cdk inactivation trigger

Answer 27

next stage of cell cycle (G1)

Question 28

what is S-cdk; what does it do

Answer 28

synthesis-cyclin dependent kinase; catalyzes phosphorylation which helps to initiate DNA replication

Question 29

what are the major cyclin-cdk complexes

Answer 29

G1-cdk, G1/S-cdk, s-cdk, m-cdk

Question 30

what cyclin associates with G1-cdk

Answer 30

cyclin D, D2, D3

Question 31

what cyclin associates with G1/S-cdk

Answer 31

cyclin B

Question 32

what cyclin associates with S-cdk

Answer 32

cyclin A

Question 33

what cyclin associates with M-cdk

Answer 33

cyclin B (M-cyclin)

Question 34

in order for the cell cycle checkpoints to be effective, what property must the cyclins and cdks have

Answer 34

sensitivity (to environment, DNA damage, chromosome attachment)

Question 35

when there is an issue with the cell cycle, what will happen to the cell

Answer 35

• it stops and withdraws from the cell cycle
• may enter G0 phase or proceed to apoptosis

Question 36

describe the G0 phase

Answer 36

• modified G1 state
• cyclins and cdks disappear

Question 37

what is apoptosis

Answer 37

programmed cell death

Question 38

x-rays are a great way to understand bone structure and health; however radiation can cause DNA damage. draw out how p53 plays a role in healthy and nonhealthy cells

Answer 38

main points:

healthy cells: p53 constantly produced and constantly degraded in proteasomes

unhealthy: p53 is phosphorylated and puts it into a stable form and acts as a transcriptional and translational activator for a gene that makes cdk inhibitor protein. cdk inhibitor protein will bind to cyclin-cdk complex and make it inactive, which stops cell cycle