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BIOLOGY NOTES 3 - A separated CDK1 repeats the...

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BIOLOGY NOTES 3 - Roles for cell divisions: o Growth and development o Reproduction] o Tissue renewal and repair - Cell divisions in microbes: exponential increase. Curved increase exponentially until the carrying point is reached. - Cell division in plants – actively dividing cells (meristematic tissue) is most frequently located in the roots of plants. Also located in the tips of buds, secondary growth in the cambium (inside the circumference of the tree beneath the trunk) CELL CYCLE - G1 & G2 are “gaps” in cell division. - Many cells in mature body organs do not actively cycle (G0) - Cycling-dependant kinases (CDK) are present in relatively equal amounts throughout the cell cycle and are activated by cyclin. Kinases phosphorelate their substrate proteins. CDK are only functional when it is bound to its appropriate cyclin. Cells cannot proceed beyond G1 into S until CDK2 has phosphorelated its targets. Cyclins are then degraded while CDK is not. Cyclin is degraded by proteins activated by CDK. At G2,
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Unformatted text preview: A separated CDK1 repeats the process.-External cell cycle control: hormones and growth factors can stimulate cells division. -Extracellular matrix connects into the cell with microfilaments; when cells touch one another, one of the responses triggered can be the ceasing of cell division. APOPTOSIS-Multicellular organisms have systems for cells to self-destruct-Example – cells between fingers and toes die in vitro; as embryos everyone has webbing between them.-Some cells are only functional after death, eg. Xylem cells of wooden plants-This process is irreversible once started-Enzymes are called caspases.-Normal cell cycling is a balance in response to external forces. -Cancer cells escape these controls; death + growth inhibition cues are ignored, survival and proliferation cures are not, uncontrolled growth is the response.-RAS – messenger protein that phosphorelates and is involved in many informational cascades....
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