LC 3.6 - Cell Cycle

Question 1

Describe growth 0?

Answer 1

Cells leave the cycle and are known as ‘post mitotic’

Eg neurones

Question 2

Name the four check points and state where they occur within the cell cycle?

Answer 2

Restriction point - G1 to S
S-phase checkpoint - S phase
G2-M phase checkpoint - G2 to M
Metaphase-anaphase checkpoint - M phase

Question 3

What factors may affect the duration of growth phase 1?

Answer 3

Extracellular signalling
Nutrient availability
Temperature

Question 4

Name and describe complex within the metaphase-anaphase checkpoint?

Answer 4

Anaphase promoting complex
Part of the proteosomal system, proteosomes breakdown and digest unnecessary/unwanted proteins and recycle their use. APC’s tag certain proteins for degradation and therefore the cell is able to continue from metaphase to anaphase

Question 5

What interdependent molecules drive the cell cycle and how do they work?

Answer 5

Cyclin dependent kinases (Cdks)
Cyclins
Cyclin-Cdk complexes polyphosphate specific target proteins

Question 6

Name the specific Cyclin-Cdk complex molecules driving through the growth 1 phase of the cell cycle?

Answer 6

Cyclin.D and Cdk.4

Cyclin.D and Cdk.6

Question 7

Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the restriction-point checkpoint (G1-S)?

Answer 7

Cyclin.E and Cdk.2

Question 8

Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the S-phase checkpoint (S-G2)?

Answer 8

Cyclin.A and Cdk.2

Question 9

Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the G2-M checkpoint?

Answer 9

Cyclin.A and Cdk.1

Question 10

Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the metaphase-anaphase checkpoint (within mitosis)?

Answer 10

Cylin.B and Cdk.1

Question 11

What are mitogens?

Answer 11

Extracellular signalling molecules that stimulate the cell cycle and thus stimulate cell division

Question 12

Name two types of mitogens?

Answer 12

Platelet derived growth factor (PDGF)

Fibroblast growth factor (FGF)

Question 13

How do mitogens act?

Answer 13

Through the MAP kinase pathway

Always act on G1/S Cyclin activity stimulation

Question 14

Describe the MAP kinase pathway?

Answer 14

Mitogen binds to cell surface receptor
Activated Ras GTPase actives MAP kinase/ERK 1
Transcription factors are synthesised - go to nucleus and stimulate protein synthesis
Myc (cMyc) produced (gene regulatory protein)
Activation of Cyclin.D and Cyclin.E

Question 15

Name the inhibitors of Cyclin.D?

Answer 15

INK4 family - p15/p16/p18/p19

Cip/kip family - p21/p27/p57

Question 16

Name the inhibitors of Cyclin.E?

Answer 16

Cip/kip family - p21/p27/p57

Question 17

Name the inhibitors of Cyclin.A?

Answer 17

Cip/kip family - p21/p27/p57

Question 18

Name the inhibitors of Cyclin.B?

Answer 18

Cip/kip family - p21/p27/p57

Question 19

What molecule is known as the ‘guardian of the genome’?

Answer 19

p53

Question 20

How does p53 work?

Answer 20

Upregulates P21 (cip/kip family inhibitors)
Arrests cell cycle (paused)
Causes apoptosis

Question 21

What are telomeres and how do they regulate the cell cycle?

Answer 21

Caps on the end of chromosomes that protects the DNA
Each time cell division occurs the telomere shortens. Once the telomere hits a certain shortened length the cell must stop dividing and undergo apoptosis (Replicative cell senescence)

Question 22

How do some cells maintain telemere length?

Answer 22

Telomerase enzyme