1.5 Flashcards
What is the function of the cytoskeleton?
Gives mechanical support and shape to cells and consists of different protein structures.
What is the structure of microtubules?
Protein structures and are hollow cylinders composed of tubulin
Where do microtubules radiate from?
The MTOC (microtubules organising centre) aka the centrosome
The formation and breakdown of microtubules involved…
Polymerisation and depolymerisation
What does cell division allow?
Allows organisms to grow, develop, replace dead cells and so repair tissues
What does the length of the cell cycle depend on?
Type of cell and external factors.
What are the two main phases of the cell cycle?
Interphase and Mitotic phase with cytokinesis
What does interphase include?
G1, S and G2
What does the M phase consist of?
Prophase, metaphase, anaphase and telophase.
What is cytokinesis?
When the two daughter cells are formed after cytoplasmic division
What happens in prophase?
Nuclear envelope breaks down and spindle microtubules attach to chromosomes.
What happens in metaphase?
Chromosomes aligned on the metaphase plate
What happens in anaphase?
Chromosomes are pulled to opposite sides by shortening microtubules
What happens in telophase?
Nuclear envelopes form round condensed chromosomes
Why are checkpoints required?
They are used to assess the cell’s condition during the cell cycle. Progression to the next phase will be halted until certain requirements are met.
Where are the checkpoints?
Near the end of G1, at the end of G2 and the metaphase of the M phase.
What do cyclins do?
Accumulate during cell growth and are involved with regulating the cell cycle
What do cyclins do with CDKs?
They combine with and activate them turning into cyclin CDKs. These complexes phosphorylase proteins that regulate protein.
What does CDK stand for?
Cyclin dependent kinases
If sufficient phosphorylation….
Progression ovcurs
If insufficient phosphorylation….
Stop
What happens at the G1 checkpoint?
Phosphorylation by G1 cyclinCDK inhibits Rb thus transcription of genes that code for the proteins needed for DNA replication takes place.
What is Rb?
Retinoblastoma protein is a tumour suppressor as it inhibits gene transcription coding for proteins needed for DNA replication.
What happens at the G2 checkpoint?
Any damage to DNA is assessed and if there is DNA damage this triggers the activation of the p53 protein.
What does activation of p53 do?
Either;
1. Stimulation of DNA repair
2. Arrest the cell cycle
3. Initiate cell death (apoptosis)
What does the M checkoint control?
Progression from metaphase to anaphase
What is progression conditional on in the M checkpoint?
The chromosomes being correctly aligned on the equator and attached to the spindle microtubules.
What causes a degenerative disease?
uncontrolled cell death
What causes a tumour?
uncontrolled cell cycle
What is a proto-oncogene?
a normal gene involved in the control of cell growth or division.
What can proto-oncogenes mutate to form and what happens next?
Tumour-promoting oncogene resulting in uncontrolled cell division
What is apoptosis?
A normal, genetically regulated process leading to the death of cells and triggered by the presence or absence of certain stimuli, as DNA damage
What is an example of an internal death signal?
DNA damage
What is activated due to DNA damage?
p53 tumour suppressor protein
What is activated due to DNA damage?
p53 tumor suppressor protein
What do external death signals do?
These molecules bind to a surface receptor protein triggering a protein cascade within the cytoplasm
What do internal and external signals end in?
The production of active caspases that cause the destruction of the cell.
Why is apoptosis important?
Remove cells during development that are no longer required as development progresses or during metamorphosis eg between fingers and toes.
