LC 3.6 - Cell Cycle Flashcards
Describe growth 0?
Cells leave the cycle and are known as ‘post mitotic’
Eg neurones
Name the four check points and state where they occur within the cell cycle?
Restriction point - G1 to S
S-phase checkpoint - S phase
G2-M phase checkpoint - G2 to M
Metaphase-anaphase checkpoint - M phase
What factors may affect the duration of growth phase 1?
Extracellular signalling
Nutrient availability
Temperature
Name and describe complex within the metaphase-anaphase checkpoint?
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
What interdependent molecules drive the cell cycle and how do they work?
Cyclin dependent kinases (Cdks)
Cyclins
Cyclin-Cdk complexes polyphosphate specific target proteins
Name the specific Cyclin-Cdk complex molecules driving through the growth 1 phase of the cell cycle?
Cyclin.D and Cdk.4
Cyclin.D and Cdk.6
Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the restriction-point checkpoint (G1-S)?
Cyclin.E and Cdk.2
Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the S-phase checkpoint (S-G2)?
Cyclin.A and Cdk.2
Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the G2-M checkpoint?
Cyclin.A and Cdk.1
Name the specific Cyclin-Cdk complex molecules driving the cell cycle through the metaphase-anaphase checkpoint (within mitosis)?
Cylin.B and Cdk.1
What are mitogens?
Extracellular signalling molecules that stimulate the cell cycle and thus stimulate cell division
Name two types of mitogens?
Platelet derived growth factor (PDGF)
Fibroblast growth factor (FGF)
How do mitogens act?
Through the MAP kinase pathway
Always act on G1/S Cyclin activity stimulation
Describe the MAP kinase pathway?
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
Name the inhibitors of Cyclin.D?
INK4 family - p15/p16/p18/p19
Cip/kip family - p21/p27/p57
Name the inhibitors of Cyclin.E?
Cip/kip family - p21/p27/p57
Name the inhibitors of Cyclin.A?
Cip/kip family - p21/p27/p57
Name the inhibitors of Cyclin.B?
Cip/kip family - p21/p27/p57
What molecule is known as the ‘guardian of the genome’?
p53
How does p53 work?
Upregulates P21 (cip/kip family inhibitors)
Arrests cell cycle (paused)
Causes apoptosis
What are telomeres and how do they regulate the cell cycle?
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)
How do some cells maintain telemere length?
Telomerase enzyme
