18 Flashcards
What is the purpose of the Cell Cycle?
Ensures cell duplicate all contents and split properly, and genetic info transfer
What are the phases of the Cell Cycle?
M Phase & Interphase
What occurs in M phase?
Nuclear and Cytoplasmic Division (mitosis & cytokinesis)
What occurs in Interphase?
Cell Growth;
G1; growth
S ; DNA synthesis
G2 ; preparation for mitosis
Cdks do what?
regulate the cycle; by phosphorylating target proteins
Ckds require what to be active?
Cyclin; triggers various cycle phases
What is the mechanism of Cdks?
activation via phosphorylation / de-phosphorylation
What are the purpose of the Checkpoints of the cycle?
They ensure proper conditions and DNA integrity before progression
- they stop the cycle under unfavourable conditions or DNA damage
What is cell cycle arrest?
cells may enter a non-dividing state (G0) if conditions are not met
What 3 main conditions are checked for at checkpoints?
- Sufficient nutrients in environment
- Chromosomes have been accurately replicated
- Chromosomes are aligned to separate properly
What is Cyclin?
a Regulatory Subunit
True or False: Cyclin concentrations stay consistent throughout cell cycle.
False: Cycling concentrations fluctuate during cell cycle
During the cycle, when are Cyclin levels low, and when do they rise?
Low after Mitosis
Rise during interphase
High M-Cyclin concentrations lead to what?
leads to active M-Cdk complex, and then to entry into mitosis
True or False: Different cyclin-Cdk complexes trigger various cell cycle stages.
True
Why mismatch between cyclin levels and M-Cdk?
What turns off M-Cdk activity?
When
How are Cdks activated?
phosphorylation by kinases and
dephosphoryaltion by phosphatases
Describe the destruction process of Cdks.
M-cyclin is tagged with ubiquitin and directed to the proteasome for degradation, leading to M-Cdk inactivation and progression to the next cell cycle stage.
If issues are detected, what occurs? (Cdk activity)
cells can halt progression or enter G0, a non-dividing state
Cdk inhibitor proteins can prevent the formation of what?
Active cyclin-Cdk complexes
What is M Phase?
The phase of the cell cycle where mitosis (nuclear division) and cytokinesis (cytoplasmic division) occur
What is Interphase?
The phase of the cell cycle between cell divisions, consisting of G1, S, and G2 phases, where the cell grows and prepares for mitosis
What is G1 Phase?
The first gap phase of interphase; the cell grows and prepares for DNA synthesis
What is S Phase?
The phase of interphase where DNA replication occurs, doubling the genetic material
What is G2 Phase?
The second gap phase of interphase; the cell prepares for mitosis by producing necessary proteins and organelles
What is G0 Phase?
A resting state where the cell exits the cycle and stops dividing, often seen in fully differentiated or non-dividing cells like neurons
What are Cyclins?
Regulatory proteins whose concentrations fluctuate during the cell cycle, activating cyclin-dependent kinases (Cdks)
What are Cdks?
Enzymes that drive the cell cycle forward by phosphorylating target proteins when activated by cyclins
What are the checkpoints?
A control mechanism ensuring that conditions are favorable for progression through the cell cycle, such as proper DNA replication and alignment of chromosomes
What are Cdk Inhibitors?
Proteins that block the assembly or activation of cyclin-Cdk complexes, halting the cell cycle when issues are detected
What is the Positive Feedback Loop?
A mechanism where an activated Cdk complex promotes further activation of upstream regulators, amplifying the signal
What is Ubiquitin?
A small protein that tags cyclins for destruction, leading to the inactivation of Cdks and progression to the next cell cycle phase
What is a Proteasome?
A protein complex that degrades ubiquitin-tagged proteins, such as cyclins
What is the DNA Damage Checkpoint?
A specific control point where the cell detects and repairs DNA damage before proceeding through the cycle
What is the Spindle Assembly Checkpoint?
Ensures chromosomes are properly attached to the mitotic spindle before separation during mitosis
What is the Mitotic Cdk (M-Cdk)?
A cyclin-Cdk complex that triggers entry into mitosis by phosphorylating key proteins for chromosome condensation and spindle formation
What is Cyclin Destruction?
The targeted degradation of cyclins (e.g., M-cyclin) by ubiquitin-proteasome pathways to reset the cell cycle machinery
What is Phosphorylation / Dephosphorylation?
The addition or removal of phosphate groups on proteins, regulating their activity and enabling cell cycle progression
What is Chromosome Alignment?
The organization of replicated chromosomes along the metaphase plate during mitosis to ensure proper separation
