KA6 -Protein Control of Cell Division Flashcards
What does the cytoskeleton give to cells?
Cytoskeleton gives mechanical support and shape to cells
What does the cytoskeleton consist of?
Different types of proteins extending throughout the cytoplasm
What are tubulins?
Microtubules composed of hollow straight rods made of globular proteins
Tubulins govern…
The location and movement of membrane-bound organelles and other cell components
Where are microtubules found?
In all eukaryotic cells
What do microtubules do?
Radiate from the centrosome (the microtubules organising centre)
What do microtubules form?
Spindle fibres, which are active during cell division
What does the cell cycle regulate?
The growth and replacement of genetically identical cells throughout the life of the organism
What may uncontrolled reduction in the rate of the cell cycle result in?
Degenerative disease
What may an uncontrolled increase in the rate of the cell cycle result in?
Tumour formation
What does the cell cycle consist of?
Interphase and mitosis
What does the interphase consist of?
An initial growth phase G1 followed by an S phase where the cell continues to grow and copies its chromosomes and a further G2 growth phase, in preparation for M phase (mitosis and cytokinesis)
What is mitosis?
A dynamic continuum of sequential changes described as prophase, metaphase, anaphase and telophase
What is the role of spindle fibres?
?
What is cytokinesis?
The separation of the cytoplasm into daughter cells
Progression through the cell cycle is regulated by checkpoints. Where?
G1, G2 and metaphase
Checkpoints are critical control points. What do they do?
Where stop and go ahead signals regulate the cycle
If a go ahead signal is not reached at the G1 checkpoint, what may happen?
The cell may switch to a non-dividing started, called the G0 phase
As cell size increases during G1, what happens?
Cyclin proteins accumulate and combine with regulatory proteins called cyclin-dependent kinases (Cdks) and activate them
What do active Cdks cause?
Phosphorylation of proteins that stimulate the cell cycle
If a sufficient threshold of phosphorylation is reached, what happens?
The cell cycle moves on to the next stage
What happens when an insufficient threshold is reached?
The cell is held at a checkpoint
What does the G1 Cdk phosphorylate? What does this allow for?
A transcription factor inhibitor - retinoblastoma (Rb) protein
This allows for DNA replication in the S phase
What does DNA damage trigger? What does this stimulate?
The activation of several proteins including the p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death
What is the most important checkpoint for many cells?
G1 checkpoint
What must be carefully controlled in a multicellular organism?
Destruction of cells
What is another name for programmed cell death?
Appoptosis
What is programmed cell death triggered by?
Cell death signals that activate inactive forms of DNAase and proteins sea (caspases) that destroy the cell
Where may cell death signals originate? Give an example. Where may they bind?
Out with the cell -
Lymphocytes
Bind to a surface receptor protein to activate a protein cascade that produces active caspases
Death signals may also originate from where? Give an example of this.
Within the cell
As a result of DNA damage the presence of p53 protein can activate a caspase cascade
In the absence of cell growth factors, what may happen?
Initiate apoptosis
