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AS Biology AQA 3.1
- Microscopy: Microscopes are instruments that magnify
the image of an object - using a convex glass (more
effective in light microscope
- Light microscope - light has a relitively long wavelength so can only distinguish between 2 objects that are 0.2um or further apart.
- This limitation can be overcome by using a beam of
electrons rather than light. e- have shorter
wavelength the electron microscope can distingush
two objects as close together as 0.1nm
- This limitation can be overcome by using a beam of
electrons rather than light. e- have shorter
wavelength the electron microscope can distingush
two objects as close together as 0.1nm
- Light microscope - light has a relitively long wavelength so can only distinguish between 2 objects that are 0.2um or further apart.
- MAGNIFICATION: material put under microscope is called the OBJECT and the material when viewed under the microscope is referred to as the IMAGE.
- Mag =size of image / size of
object
- Size of object=size of
image/magnification
- MAKE SURE YOU USE THE SAME UNITS (COVERT)
- MAKE SURE YOU USE THE SAME UNITS (COVERT)
- Mag =size of image / size of
object
- Resolution (or resolving power). = Min distance apart 2 items can be in order 4
them 2 b distinguished as 2 separate items. Light microscope: items at least 2um
apart can ve seen seperately.
- Greater resoultion = GREATER CLARITY
- Greater resoultion = GREATER CLARITY
- Cell Fractionation: process where cells R broken up in2 diff organelles they contain & seperated out
- The tissue must be in a cold buffer solution b/c: Cold - reduction of enzyme activity. Isotonic - prevention of organelles bursting b/c of osmotic gain or loss of water. Buffered - constant pH.
- ISOTONIC: same water potential as original tissue.
- ISOTONIC: same water potential as original tissue.
- Homogenation: Cells r broken up by a homogeniser (blender). This releases d organelles from d cell . Resultant fluid -homogenate filtrd 2 remove any complete cells & large debris.
- Untracentrifugation: procedd by which fragments in d filtrd Homogenate seperated in machine called
ultracentrifuge. spins tubes @ v high speed nd creates centrugal force. 4 Animal cells: Tube of filtrate placed in
Ucentrifuge. spun at low speed. Then heaviest organelled -nuclei forced 2 bottom of tube. fluid at d top
(supernatant) removed. D supernatant transferred 2 diff tube @ faster speed than b4. Nxt heaviest organelles -
mitochondria forced 2 bottom of d tube. Process carries on etc, so tht nect heaviest organelle left @ bottom of
tube.
- 1. Nuclei. 2. Mitochondria. 3. Lysosomes. 4.Ribosomes
- 1. Nuclei. 2. Mitochondria. 3. Lysosomes. 4.Ribosomes
- The tissue must be in a cold buffer solution b/c: Cold - reduction of enzyme activity. Isotonic - prevention of organelles bursting b/c of osmotic gain or loss of water. Buffered - constant pH.
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