cell cycle

Adult Stem Cells Enter The Cell Cycle Only When The Body Needs New Cells

Defective Cells ThatCan’t Be Repaired Are Eliminated (Self-Destruct) ~ Apoptosis


Cell Cycle Checkpoints Are Internal Cellular Mechanisms That Control Cell Cycle Progression
 -They Search For, Detect, And Repair Biochemical Errors

At Each Checkpoint, The -
•Cell Cycle Pauses
•Checkpoint Sensors Search For A Factor Or Biochemical Error
•Cell Cycle Continues If Factor Is Detected Or No Errors Detected


Cyclin Proteins & Cyclin-Dependent Kinases (CDKs) Are The Regulatory Molecules That Control Cell Cycle Progression
•They Enable The Cell To Advance To The Next Phase
•Cyclin Binds To CDK To Activate It
•Activated CDK Phosphorylates Proteins That Enable Progression

When a protein has finished its job they need to be cleaned up so the next job can happen, proteasome is what picks up the now useless proteins and breaks them down into smaller pieces. One important protein is cyclin, it help the cell move from one step to the next but once the job is done Ubiquitin tells the proteasome that the cyclin needs to be thrown away. If the proteasome doesn’t work properly then the cycle will get all messy and there is risk of problems like too many cyclin staying around and not doing the right job. And this mess can lead to things like cancer.



In apoptosis, the cell undergoes a carefully regulated process where it breaks down its components in an organized manner. The cell’s DNA is fragmented, its proteins are dismantled, and the cell shrinks and is eventually engulfed by neighboring cells or immune cells. This controlled process ensures that the cell dies without releasing harmful contents into the surrounding tissue, preventing inflammation or damage to neighboring cells.


Defective Cell Cycle Regulation Has Medical Consequences
 - Abnormal Growth, Benign Tumors, Malignant Tumors (Cancer), Immune System Dysfunction






STUDY GUIDE QUESTIONS


What Is The Function Of Each Cell Cycle Checkpoint?
G1 Checkpoint : is the cell growing well enough? Is its DNA damaged? - if it is we wouldnt want it to move onto S phase where you would replicate the DNA- Does the cell have the resources it needs if it were to keep moving on?
G2 checkpoint: Checks to see if the DNA was replicated correctly back in S phase. Is it growing well enough? Does It have the resources it needs to continue? 
M phase checkpoint: It checks in the stage metaphase to make sure that chromosome which are made up of DNA are lined up in the middle correctly, that they are all attached to the spindle correctly because if theyre not the chromosomes will not be separated correctly.

•Do Some Cancer Cells Ignore One Or More Checkpoints?
Yep

•Do Some Mutations Inactivate The Checkpoints?
Yes 

•Can Cancer Result From One Or More Defective Cell Cycle Checkpoints?
Yes

 
Which Biochemical Errors Activate The Checkpoints?
DNA damage, Incomplete DNA replication or cell size issues 

 
A Checkpoint Is Activated Due To A Biochemical Error Will The Adult Stem Cell Enter The Next Phase After Repair?
Yes 

A Checkpoint Is Activated Due To A Biochemical Error Will The Cell Self-Destruct By Apoptosis If The Error Can’t Be Repaired?
Yes, and it is in a controlled manner no explosion it can be dangerous to surrounding cells 

 
What Is Apoptosis? Can Mutations Prevent Apoptosis In Cancer Cells?
Self destruction in a controlled manner, yes mutations can precent apoptosis from happening 

 
What Are Cyclins?
proteins that regulate the cell cycle,They help control the progression of the cell from one phase to the next.


 What Are CDKs?
CDKs need cyclins to function: Cyclins are proteins that bind to CDKs, activating them. Without cyclins, CDKs are inactive.
Once activated by cyclins, CDKs phosphorylate (add phosphate groups to) other proteins that are involved in different steps of the cell cycle. This phosphorylation helps push the cell to the next phase.


 
What Is The Function Of Proteasomes?
proteasome is what picks up the now useless proteins and breaks them down into smaller pieces.



•Adult Stem Cells Must Recognize A Go-Signal To Pass Which Checkpoint?
"Go" signals drives the cells to move from the G1 phase into the S phase, where DNA replication occurs. If these signals are not present or the cell is not ready, the stem cell will remain in a quiescent or dormant state (often in G0 phase) until the necessary conditions are met.