Unit III Test Flashcards
What is a protein Kinases
Protein kinases are enzymes that activate or inactivate other proteins by phosphorylating them.
What makes a Kinase active?
For a kinase to be active it must be attached to a cyclin.
What is Cyclin?
a cellular protein that occurs in a cyclically fluctuating concentration. It plays a key role in regulating the cell cycle.
What is a CDK?
(Cyclin-Dependent-Kinase)- A protein kinase that is active only when attached to a particular cyclin.
What causes CDK to rise and fall?
The activity of CDK rises and falls with changes in the concentration of its cyclin partner.
What is Phosphorylation?
Phosphorylation is often carried out by enzymes called kinases, which transfer a phosphate group from a molecule called ATP (adenosine triphosphate) to the target molecule.
What is “MFP”(M-phase-promoting-factor)
It triggers the cell’s passage into the M phase, passed the G2 checkpoint. MFP acts both directly as a kinase and indirectly by activating other kinases. The peaks of MFP activity corresponds to the peaks of cyclin concentration
What happens when Cyclins accumulate during the G2 checkpoint and associate with the CDK molecules?
The resulting MFP complex is active–it phosphorylates a variety of proteins which initiates mitosis.
Why is fluctuation of different cyclin-CDK complexes important?
It is important because it controls all the stages in the cell cycle; they also give the go-ahead signals at some checkpoints.
Why is the G1 check point important for most cells?
The G1 check point is the most important because, if a cells receives a go-ahead signal at the G1 checkpoint, it will usually complete the G1,S, G2, and M phases and divide. If it does not receive a go-ahead signal, it may exit the cycle, switching into a non-dividing state called G0 phase.
What is the G1 check point?
It serves as a decision point for a cell to either continue progressing through the cell cycle and prepare for DNA replication and division or exit the cell cycle. At the G1 checkpoint, the cell assesses its internal and external conditions to ensure that it is ready to commit to another round of cell division
What are the four factors that effect the passage through the G1 check point?
1.) the cell size
2.) nutrient availability
3.) DNA integrity
4.) growth factors and signaling
What happens if DNA is damaged?
The p53 protein either activates proteins that pause the cell cycle until damage can be repaired
Or initiates apoptosis = programmed cell death
Helicase
Unwinds parental double helix at replication forks
Single Strand binding protein
Binds to and stabilizes single stranded DNA until it is used as a template
