Cell Division & the Cell Cycle Flashcards
In what way is apoptosis important during the development of an organism?
Uncontrolled diseases in the rate of the cell cycle could lead to degenerative diseases. An uncontrolled increase in the rate of the cell cycle could lead to tumour formation.
What are caspases and what role do they play in apoptosis?
Caspases are proteases. They digest the protein contents of the cell. Caspases are the cause of cell death during apoptosis.
What is the function of the cytoskeleton?
Provides mechanical support and shape to the cells. The cytoskeleton is responsible for moving organelles around inside the cell. The reorganisation of the cytoskeleton also allows white blood cells to change shape.
What is the main protein that the cytoskeleton is made up of?
It consists of different protein structures including microtubules, which are found in all eukaryotic cells. Prokaryotic cells do not contain microtubules.
What are microtubules?
Microtubules are hollow cylinders composed of the protein tubulin. Microtubules radiate from the microtubules organising centre(MTOC) e.g. a centrosome.
How are chromosomes moved in the cell?
Spindle fibres (made of microtubules) pull the chromosomes to opposite poles in the cell by shortening due to the depolymerisation of tubulin.
What are the 2 main stages in the cell cycle?
Interphase and M phase (mitosis)
What are the stages of mitosis? (in order)
Prophase, metaphase, anaphase, telophase, cytokinesis.
What are checkpoints and what happens at them?
Checkpoints are the mechanisms within the cell that assess the condition of the cell during the cell cycle and halt the progression to the next phase until certain requirements are met.
How are cyclins involved in regulating the cell cycle?
Cyclin proteins that accumulate during cell growth are involved in regulating the cell cycle. Cyclins combine with and activate cyclin-dependent kinases (CDKs). Active cyclin-CDK complexes phosphorylate proteins that regulate progression through the cycle. If sufficient phosphorylation is reached, progression occurs.
What happens at a 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. Phosphorylation by G1 cyclin-CDK inhibits the Rb protein. This allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase.
What does apoptosis mean?
Apoptosis is programmed cell death.
How can apoptosis be triggered?
Apoptosis is triggered by cell death signals. These can be internal or external.
Internal - DNA damage is the main cause of internal death signals
External - Lymphocytes produce cell death signals to initiate apoptosis in infected cells.
What is the role of p53 in apoptosis?
An internal death signal resulting from DNA damage causes activation of p53 tumour suppressor protein.
What happens during the G2 checkpoint?
The success of DNA replication and any damage to DNA is assessed. DNA damage triggers the activation of several proteins (p53) that can stimulate DNA repair, arrest the cell cycle or cause cell death.
