Protein control of cell division Flashcards
Function of the cytoskeleton
The cytoskeleton gives mechanical support and shape to cells
What does the cytoskeleton consist of?
It consists of different protein structures including microtubules, which are found in all eukaryotic cells
Function of microtubule
Microtubules control the movement of membrane-bound organelles and chromosomes
What does cell division require?
Cell division requires remodelling of the cytoskeleton
Formation and breakdown of microtubules involves?
polymerisation and depolymerisation of tubulin
Microtubule can form?
spindle fibres that are active during cell division
The cell cycle consists of?
interphase and mitotic (M) phase
Mitotic phase consists of?
mitosis and cytokinesis
Mitosis consist of?
prophase, metaphase, anaphase and telophase
How to control progression of cell cycle?
checkpoints
What are cyclins?
Cyclins are proteins that accumulate during cell growth are involved in regulating the cell cycle
What happens at G1 checkpoint?
At the G1 checkpoint, retinoblastoma protein (Rb) acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication
What is the goal of mitosis?
To make identical cells
How to inhibit retinoblastoma proteins? Why?
Phosphorylation by G1 cyclin-CDK. This means that it can no longer bind the transcription factor. This allows transcription of the genes that code for proteins needed for DNA replication and allows cells to progress from G1 to S phase.
What does non-phosphorylated form of Rb do?
restricts progression from G1 phase into S phase by binding to a transcription factor, therefore preventing transcription of certain genes required for S phase to begin; thus the cell remains in G1
What is the G2 checkpoint?
At the G2 checkpoint, the success of DNA replication and any damage to DNA is assessed
What happens if there is DNA damage?
DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death
What happens at metaphase checkpoint?
A metaphase checkpoint controls progression from metaphase to anaphase
What can cause a degenerative disease?
An uncontrolled reduction in the rate of the cell cycle
What can cause tumour formation?
An uncontrolled increase in the rate of the cell cycle
What is a proto-oncongene?
It is a normal gene, usually involved in the control of cell growth or division, which can mutate to form a tumour-promoting oncogene
Apoptosis is triggered by what?
is triggered by cell death signals that can be external or internal
What is an external death signal molecule?
bind to a surface receptor protein and trigger a protein
cascade within the cytoplasm
What is an internal death signal molecule? What causes it?
An internal death signal resulting from DNA damage causes activation of p53 tumour suppressor protein
What do both types of death signals activate?
Both types of death signal result in the activation of caspases that cause the destruction of the cell
What are caspases
types of protease enzyme
Why is apoptosis essential?
Apoptosis is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis
Why might cells initiate apoptosis?
Cells may initiate apoptosis in the absence of growth factors
Prophase?
DNA condenses into chromosomes each consisting of two sister chromatids.
Nuclear membrane breaks down; spindle microtubules extend from the MTOC by polymerisation and attach to chromosomes via their kinetochores in the centromere region.
Metaphase?
Chromosomes are aligned at the metaphase plate (the term metaphase plate is used to describe the arrangement of the chromosomes at the equator of the cell)
Anaphase?
As spindle microtubules shorten by depolymerisation, sister chromatids are separated, and the chromosomes are pulled to opposite poles
Telophase
The chromosomes decondense and nuclear membranes are formed around them.
Cytokinesis also takes place during this period, which involves the separation of the cytoplasm into two daughter cells
Interphase sub phases?
G1, S and G2
G1 phase?
G1 is the first ‘growth’ phase; it is a growth period where proteins and organelles are synthesised.
S phase?
DNA is replicated in preparation for mitosis
G2 phase?
this is another growth period during which proteins and organelles are synthesised
