Cell Cycle

Question 1

what is cell proliferation ?

Answer 1

• cell grows + divides to produce 2 daughter cells

Question 2

what are the three main types of cells (growth) ?

Answer 2

• labile cells
• stable cells
• permanent cells

Question 3

what are labile cells + example ?

Answer 3

• constantly dividing
• epithelial cells

Question 4

what are stable cells + example ?

Answer 4

• low rate of division normally but can rapidly divide in response to injury or stimuli.
• eg. hepatocytes

Question 5

what are permanent cells ?

Answer 5

• permanently differentiated so unable to divide
• eg. neurons

Question 6

what is an example of illness with decreased proliferation and increased cell death ?

Answer 6

• chronic wound

Question 7

what is an example of illness with increased proliferation and decreased cell death ?

Answer 7

• cancer

Question 8

what are the 3 stages of the cell cycle ?

Answer 8

• Interphase
• Mitosis (nuclear division)
• Cytokinesis (cytoplasm division)

Question 9

what are the stages of interphase ?

Answer 9

• G1 phase (gap 1 )
• S Phase
• G2 phase

Question 10

what happens during the G1 phase ?

Answer 10

• cell grows before DNA synthesis
• synthesizes proteins + organelles

Question 11

what happens during the S Phase ?

Answer 11

• DNA replication

Question 12

what happens during the G2 Phase ?

Answer 12

• after DNA synthesis, lasts until cell division

Question 13

what is G0 phase ?

Answer 13

• cells can enter G0 from G1 if conditions aren’t favourable
• resting phase
• do not divide

Question 14

what cells are permanently in the G0 Phase ?

Answer 14

• nerve cells

Question 15

what are the 5 Phases of Mitosis ?

Answer 15

• prophase
• prometaphase
• metaphase
• anaphase
• telophase

Question 16

what happens during prophase ?

Answer 16

• chromosomes condense
• nucleolus disappears
• centrioles move to opposite poles

Question 17

what happens during prometaphase ?

Answer 17

• spindle fibers / micro tubules attach to centromere
• chromosomes fully condense

Question 18

what happens during metaphase ?

Answer 18

• chromosomes align at equator

Question 19

what happens during anaphase ?

Answer 19

• centromere divides
• sister chromatids are pulled to opposite poles

Question 20

what happens during telophase ?

Answer 20

• nuclear membrane reforms
• chromosomes decondense

Question 21

what happens during cytokinesis ?

Answer 21

• cytoplasm divides
• 2 daughter cells produced

Question 22

what is the role of G1 checkpoint ?

Answer 22

• checks if cell is large enough
• if environment is favourable
• checks DNA for damage

Question 23

what is the role of the
G2 checkpoint ?

Answer 23

• checks duplicated DNA for any damage
• checks cell size

Question 24

what is the role of the M (metaphase) checkpoint ?

Answer 24

• checks all chromosomes are aligned and attached to spindle fibers

Question 25

How CDK's (Cyclin Dependent Kinases) activated ?

Answer 25

- Cyclin binds to CDK exposing its active site - protein substrate and ATP bind to CDK active site - protein substrate is phosphorylated - phosphorylated protein regulates cell cycle at different stages

Question 26

Phosphorylation of Rb protein?

Answer 26

- mitogens activate cyclin D - Cyclin D binds to CDK 4/6 - CDK 4/6 phosphorylates Rb protein - Rb protein is attached to E2F (transcription factor) - phosphorylation of Rb inactivates it - E2F is released and switches on cell cycle