Cell Cycle Flashcards
The cell cycle is for what?
The growth and division of a cell.
Cells divide for what purpose?
When they need to replace injured or dead cells, or for generally a development of an organism.
The cell cycle is mostly divided into two phases called what?
Interphase and M Phase
What is the longest event in the cell cycle?
Interphase
It enables the cell to grow.
Interphase
What are the stages of Interphase?
G1, S, and G2
What is the meaning of “G” in G1 and G2?
Gap
Why is it called Gap 1 and Gap 2?
Scientists couldn’t see anything happening during other parts of interphase, so they named the periods between mitosis and synthesis as literal gaps of inactivity until later discoveries.
The cell grows larger in this stage, duplicates organelles, and develops building blocks.
G1
DNA replication and duplication of centrosomes occur.
Synthesis
Cell grows continuously, making more proteins, duplicating organelles, and completing the preparations for the next phase.
G2
What stage makes up the loss of energy during S phase?
G2
Duplication and division happens.
M Phase
Under this phase, you also have cytokinesis.
M Phase
Distribution of chromosomes into two daughter nuclei.
Mitosis
Division of the cytoplasm producing two daughter cells.
Cytokinesis
Division of the nucleus into two new nuclei.
Karyokinesis
In one round of the cycle, what happens to the two daughter cells?
It either enters G1 phase and G0 phase.
If a cell enters G1 phase, what happens?
It prepares for cell division again, hence it being a cycle.
Why would a cell enter the G0 phase?
There are:
Unfavorable environmental conditions
Waiting for a signal
A permanent state (Like nerve or cardiac muscles)
What cells don’t divide?
Cardiac and nerve cells since they only can grow.
Why do nerve cells don’t divide?
Lack of centrosomes (Provides structure)
The whole cycle takes?
24 Hours
How long is the G1 phase?
5 to 6 hours
How long is the S phase?
10 to 12 hours
How long is the G2 phase?
4 to 6 hours
How long is the M phase?
Approximately 1 hour
What is the longest stage in the interphase?
Synthesis
Why is the longest stage in the interphase synthesis?
Because of the complexity of the genetic material being duplicated.
What is the shortest phase of the cell cycle?
M phase
In the cell cycle, what mostly controls it?
Regulatory proteins: CDK, Cyclin, and p53
What is the activating protein that binds to a kinase to form CDK complex.
Cyclin
What undergoes a constant cycle of synthesis and degradation during cell division?
Cyclin
What is the meaning of CDK?
Cyclin-Dependent Kinase
If there is no Cyclin, what will happen to a CDK?
Hence it’s name, it’s dependent on it.
If Cyclin is not present, it will be inactive.
This regulatory protein activates or deactivates another protein by phosphorylating them.
CDK Complex
How does CDK activate and deactivate other proteins?
By phosphorolysis.
Introducing a phosphate group.
Phosphorolysis
What is the purpose of phosphorylating of CDK Complex?
It gives the ‘ stop’ and ‘ go’ signal at the Gap 1 and Gap 2 checkpoints.
It is responsible for suppressing tumors, repairing damaged DNA, and triggering apoptosis of damage is beyond repair.
p53
What does the p53 signal to release when DNA damage is detected?
CDK inhibitor
What is apoptosis?
Cell death if cell is not fixable.
It initiates mitosis.
MPF Complexes (It is a maturation-promoting factor whenever there is an abundance of both CDK + m cyclin).
When the cyclin in the MPF complex is degraded, what happens to mitosis?
It ends
The MPF complex also plays a role in activating another protein complex that is responsible for degrading the M cyclin. What is this protein complex?
APC/C (Anaphase-promoting complex/cyclosome)
Is the environment favorable?
G1 Checkpoint
In the G1 Checkpoint, what do we mean by favorable environmental conditions?
Nutrients and Protein Reserves
Sufficient Cell Size
Intact Genetic Material
The most important checkpoint?
G1 Checkpoint
What happens if the cell’s environment is favorable but does not proceed S phase?
The cells differentiate wherein it turns into a more specialized cell.
Does the S Phase have a checkpoint?
No.
Is the environment favorable?
Is all DNA properly replicated?
G2 Checkpoint
In the G2 Checkpoint, what do we mean by favorable environmental conditions?
Sufficient cell size
Intact genetic material
Are all chromosomes attached to the spindle microtubules?
M checkpoint
What could be the result of not having chromosomes attached to the spindles?
Chromosomal syndromes
What would happen if these regulatory proteins fail?
Cancer cells would arise, dividing uncontrollably and forming tumors.
When cells are not dividing, their DNA exists as?
Chromatin in the Nucleus
What’s more complex in cell division? Prokaryotes or Eukaryotes
Eukaryotes
Does cytokinesis occur the same way in all cells?
No. It differs between plant and animal cells. In a plant cell, a cell plate forms.
Cell stays dormant
G0 Quiescent
Cell ages or deteriorates
G0 Senescent
