Ch.17-Cell Cycle and Programmed Cell Death

Question 1

1. Describe the cell cycle including the different phases that occur during mitosis

Answer 1

G1&raquo_space; S&raquo_space; G2&raquo_space; M (mitosis and cytokinesis)

• Mitosis: Prophase, metaphase, anaphase, telophase

Question 2

2A. Describe the processes that occur during the G1 phase

Answer 2

= long resting phase; most cells in this stage

Question 3

2B. Describe the processes that occur during the S phase

Answer 3

= DNA replication

Question 4

2C. Describe the processes that occur during the G2 phase

Answer 4

= short resting phase, has 96 chromosomes

Question 5

2D. Describe the processes that occur during the M phase

Answer 5

= mitosis (nuclear division), cytokinesis (cytoplasmic division)

Question 6

3A. What are cyclin dependent kinases?

Answer 6

= protein kinases (enzymes that phosphorylates proteins) that need to bind to cyclin in order for it to be activated

Question 7

3B. What is their role of cyclin dependent kinases in the cell cycle?

Answer 7

• Control the cell division cycle

- phosphorylates other proteins

Question 8

4. What are cyclins?

Answer 8

= The protein that controls whether Cdk are active

Question 9

5. List the different cyclins involved in the cell cycle and the processes they control.

Answer 9

1. G1 cyclin
2. G1/S cyclin
3. S cyclin
4. M cyclin

Question 10

6A. What are Cdk inhibitory proteins?

Answer 10

= proteins that inactivate cyclin dependent kinases by binding to active Cdk

Question 11

6B. What does p27 do?

Answer 11

= is a type of Cdk inhibitory protein

Question 12

7. How else can Cdk’s be inactivated?

Answer 12

• By inhibiting phosphorylation&raquo_space;> phosphorylation twice = inactive
• Can be labeled with ubiquitin and degraded

Question 13

8A. What is APC?

Answer 13

= Anaphase promoting complex; It is activated by M-Cdk

Question 14

8B. What does APC do?

Answer 14

= Activates separase (cuts cohesive proteins); degrades M-cyclin, which deactivates M-Cdk

Question 15

9. How come a cell in G1 phase that has assembled the pre-replicative complex does not immediately go in to the S-phase?

Answer 15

A signal molecule is required??

????????

Question 16

10A. Describe the role of cyclins G1 in moving a cell from the G1-phase to the S-phase.

Answer 16

1. makes active Cdk complex that forms G1/Cdk;
2. phosphorylates Rb protein;
3. released more E2F;
4. increase in G1/S and S cyclin

Question 17

10B. Describe the role of cyclins G1/S in moving a cell from the G1-phase to the S-phase.

Answer 17

makes active G1/S Cdk

Question 18

10C. Describe the role of cyclins S in moving a cell from the G1-phase to the S-phase.

Answer 18

1. makes active S Cdk;
2. phosphorylates inhibitory protein attached to pre-replicative complex;
3. releases from pre-replicative complex and DNA replication starts.

Question 19

11A. Describe the role of the Myc protein.

Answer 19

= DNA binding protein that increases transcription of: G1 cyclin gene, SCF gene (which decreases P27) and E2F

Question 20

11B. Describe the role of the E2F.

Answer 20

= DNA binding protein that causes an increase in S cyclin, binds to Rb protein to cause “brake”

Question 21

11C. Describe the role of the Ras protein.

Answer 21

= Map kinase  DNA binding protein increases transcription of Myc gene

Question 22

12. What is an Rb protein?

Answer 22

• A “brake” for cell division cycle; it does this by binding to the E2F protein
• Active G1-CDK complex phosphorylates Rb protein, which causes it to change shape so that it no longer has an affinity for E2F

Question 23

13. What is the pre-replicative complex?

Answer 23

• Assembled in the G1 phase
• Specific spot on chromosome where DNA replication starts
• Many proteins that are inactive when inhibitory proteins are bound to it

Question 24

14A. What is p53 and what does it do?

Answer 24

= A tumor suppressor protein

- it increases transcription of inhibitory protein genes&raquo_space;> inhibitory proteins deactivate Cdk complexes

Question 25

14B. How is p53 activated?

Answer 25

= DNA damage, excessive mitogenic stimulation

Question 26

14C. Why can mutations in p53 lead to cancer?

Answer 26

= p53 gene mutation can make so the cell never stops dividin

Question 27

15. What is apoptosis?

Answer 27

= Programmed cell death

Question 28

16. What proteins mediate apoptosis?

Answer 28

1. Procaspases | 2. Caspases

Question 29

17A. How are procaspases and caspases proteins activated? | (INTRINSIC pathway

Answer 29

= Cytochrome c is released from mitochondria >>> procaspases form aggregates >>> results in activation of first group of caspases

Question 30

17B. 17A. How are procaspases and caspases proteins activated? (EXTRINSIC pathway)

Answer 30

= Killer lymphocyte has membrane protein that binds receptor in target cell >>> Trigger activation of procaspases

Question 31

18. What are mitogens?

Answer 31

- Signal molecules that induce or stimulate mitosis, causes cell division - Binds to enzyme linked receptor

Question 32

19. Why would an activated blood platelet secrete mitogens?

Answer 32

So other blood platelets can undergo cell division and create a primary plug

Question 33

20A. What is a Ras protein?

Answer 33

= Map kinase >>> DNA binding protein increases transcription of Myc gene

Question 34

20B. What is a myc protein?

Answer 34

= DNA binding protein

Question 35

21. What is a growth factor?

Answer 35

= Protein or steroid hormone that stimulates growth, proliferation, healing and cellular differentiation

Question 36

22. What is a survival factor?

Answer 36

They bind to receptors >>> kinase activated >>> phosphorylate and inactivate proteins that cause apoptosis

Question 37

23. How does an organism ensure that each nerve cell is attached to a target cell?

Answer 37

Target cells will release survival factors to make sure nerve cell survives to attach to it

Question 38

24. How does an organism ensure that extra nerve cells are eliminated?

Answer 38

-Target cell will release survival factors but only the nerve cells that are closest to the target cell will receive it—all extra nerve cells will not receive survival factors and undergo apoptosis

Question 39

25. What is cancer?

Answer 39

= Uncontrolled cell division

Question 40

26. What is metastasis?

Answer 40

= When cancer cells start to move-spreading throughout the body-becomes more malignant

Question 41

27. Is a single mutation sufficient to give rise to cancer? Why?

Answer 41

No, it is caused by slow accumulation of numerous mutations

Question 42

28. How could over-activity of a protein or gene contribute to cancer? Give an example of a protein that could contribute to cancer if over active.

Answer 42

Over-activity of the myc or ras protein would cause too much cell division to occur

Question 43

29. How could elimination of a gene contribute to cancer? Give an example of a protein that could contribute to cancer if absent.

Answer 43

1. Elimination of P53 gene: = could no longer stop cell division 2. Elimination of Rb gene: = Wouldn’t stop E2F-DNA replication would continue to occur