3.7 Cell Cycle

Question 1

Motor proteins use ___ to power transport along the microtubule “railroad”

Answer 1

ATP

Question 2

ATP binding makes actin ___ more easily at the ___ end

Answer 2

polymerize
+ end

Question 3

___ enables cytokines

Answer 3

Contractile ring formation of overlapping actin and myosin filaments

Question 4

ATPase activity increeases once bound in ___

Answer 4

Filaments

Question 5

Myosin moves what?

Answer 5

Membranes or cell components

Question 6

Muscle is contracted by

Answer 6

Actin and myosin

Question 7

Most important cell cycle checkpoints:

Answer 7

Enter S phase
Enter Mitosis

Question 8

Describe “enter S phase” check point

Answer 8

Is the environment favorable?
Is it ready to replicate?

Question 9

Describe the “enter Mitosis” phase

Answer 9

Is all DNA replicated?
Is environment favorable?

Question 10

Phosphorylation allows ___ signals to control ___ protein activity

Answer 10

Extracellular
Intracellular

Question 11

Reversible covalent modifications turn proteins on, off, or both? What can do this?

Answer 11

Both

Kinase and phosphatase

Question 12

Extracellular signals can control intracellular protein activity by activating ___ activators or ___

Answer 12

Allosteric activators or inhibitors

Question 13

The cell cycle is controlled by ___

Answer 13

Cdk

Question 14

Function of Cdk. How does it become active?

Answer 14

• Cdk phosphorylates cell targets that enter different parts of cell cycle
• Requires cyclin binding to form Cdk complexes (it allosterically binds)

Question 15

How does Cdk become fully active?

Answer 15

Cdk-activating kinase (CAK) phosphorylates Cdk

Question 16

G1-Cdk is a cyclin type for what role?

Answer 16

Advance G1

Question 17

G1/S-Cdk is a cyclin for what phase?

Answer 17

Entry into S phase

Question 18

S-Cdk is a cyclin for what phase?

Answer 18

DNA replication

Question 19

M-Cdk is a cyclin for what phase?

Answer 19

Entry into mitosis

Question 20

What are the 3 ways to control Cdk activity?

Answer 20

• Cyclin concentration
• Cdk phosphorylation controls activity
• Cdk inhibitor proteins can inhibit Cdk-cyclin complex formation (cyclin binding)

Question 21

Explain the regulation of cyclin concentration

Answer 21

• Cyclin protein expression
• Degradation of existing cyclin

Question 22

Explain how Cdk phosphorylation controls activity

Answer 22

Activating and inactivating kinases and phosphatases act on Cdk to regulate activity

Question 23

___ control entry into S phase and mitosis

Answer 23

Mitogens

Question 24

Steps for mitogen causing release of Myc

Answer 24

1. Mitogen binds to receptor on plasma membrane
2. Changes conformation and binds to accessory protein (Ras)
3. Binds to MAP kinase
4. Causes MAPK cascade
5. Phosphorylates proteins that can go into nucleus and binds to immediate early genes
6. Immediate early gene product binds to promoters of early genes
7. Causes expression of genes (gene regulatory proteins like Myc)
8. Myc causes expression of cyclins

Question 25

lmmediate early genes expression upregulates transcription of ___

Answer 25

Delayed genes

Question 26

The last protein that is phosphorylated by MAP kinase goes where?

Answer 26

Into the nucleus

Question 27

What happens if you change the phosphorylation state of a Cdk?

Answer 27

It alters Cyclin/Cdk complex activity

Question 28

Cdk is activated by

Answer 28

Phosphatase

Question 29

Cdk is inactivated by

Answer 29

Kinase

Question 30

___ transcription factor causes expression of genes that drive entry into ___ phase

Answer 30

E2F
S phase

Question 31

___ holds E2F inactive until phosphorylated by G1-Cdk

Answer 31

Rb (retinoblastoma)

Question 32

Steps for inactivation and activation of E2F

Answer 32

1. Rb inhibits E2F activation
2. G1 phosphorylates Rb
3. E2F falls off
4. E2F is active and starts S phase gene transcription

Question 33

DNA damage halts cell cycle by activating ___

Answer 33

p53

Question 34

p53 function

Answer 34

detects damaged DNA and stops it G1 from entering S phase in interphase, which prevents replication of bad DNA

Question 35

p53 activates ___ to do what?

Answer 35

p21 gene, which encodes an inhibitory protein for G1 and S Cdks

Question 36

What happens if p53 is mutated?

Answer 36

There are more damaged cells
- Malignant tumors have inactive p53

Question 37

___ patches chromosome ends

Answer 37

Telomerase

Question 38

Define telomerase

Answer 38

• Maintains chromosome length
• Has its own RNA template and keeps telomeres longer