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13 Cards in this Set
- Front
- Back
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What is sub-cellular fractionation? |
Separation of different organelles in largenumbers. Necessary for biochemical studies oforganelle function. |
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Cells must be physically disrupted, after this what happens to them? |
• Disrupted cells must be heldin solution with similar pH,salt content and tonicity tointerior of cell. (Sucroseoften used to make isotonicsolution). • Keep them cold!! |
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How are cells separated by Differential-velocity centrifugation? |
Centrifugation atsuccessivelyincreased speeds(increasedcentrifugal force)pellets differentsubcellularfractions. Differential-velocity centrifugation does not give pure fractions. |
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How are cells separated in Equilibrium-density centrifugation? |
• Can give further purificationof differential velocitycentrifugation fractions. • Separates according todensity. • Testing for organelle specificmolecules canassess purity of organelles:e.g. Catalase forCytochrome c for |
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Which properties influence the behaviour of cellcomponents in a centrifugal field? |
• For each cell component its behaviour can be given avalue: s = the sedimentation constant(expressed in Svedberg Units) e.g. 70S ribosome (prokaryotes) |
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What are the features of eukaryotic cells? |
• Have DNA in a membrane-enclosednucleus. • Also have membrane-bound cytoplasmicorganelles and a cytoskeleton. • Cells 5 – 50 µm, but size and shape veryvariable |
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What is the first stage in embryo growth? |
1. Cell division |
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What us the next stage? |
2. Cell movement Gastrulation –illustrated here inXenopus laevis A simple ball of cells becomes a three-layered structure |
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What do fate maps show? |
‘Fate maps’ show the origin ofembryonic tissues |
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What happens after gastrulation? |
3. Cell signalling Experiments show thatmolecular signalspass from one part ofthe embryo to another:‘embryonic induction’. |
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What induces the development of the lens of the eye? |
Signals from underlying forebrain tissue inducedevelopment of the lens of the eye. |
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How do cells become specialised? |
Stem cells ----> differentiation ---> Neurons andglial cells |
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What are the last stages of foetal development? |
Gene expression Cell death |
