3.1,2&3- Analysis of cell components

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  • Created by: Megan2413
  • Created on: 22-11-16 17:58
What is magnification?
It's how much bigger the image is that the specimen
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What is the formula for magnification?
Magnification = image size/actual size
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What is resolution?
The minimum distance apart two objects can be in order for them to appear as two items
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What is the formula when dealing with scale bar calculations?
Actual size = image length/length of bar x value of scale bar
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What is a graticule?
A ruler used to measure the size of a cell on a microscope (in micrometres)
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What are the two main differences between how each microscope works?
The optical microscope uses a beam of light to form an image whereas the electron microscope uses a beam of electrons
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List 3 advantages of using a light microscope
- Cheaper - Produces colour images - Specimens can be living or dead
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List three disadvantages of using a light microscope
- Specimens have to be cut thinly for the light ot pass through - A stain needs to be used to make parts visible - Can't see single organelles as resoltuion is too low -
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List 3 advantages of using an electron microscope
- Electrons produce higher resolution image - As electrons are negatively charged electromagnets can be used to focus the beam onto the fluorescent screen - Higher magnifications can be used - 3D images produced - Doesn't need a thin sample
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List 3 disadvantages of using an electron microscope
- A lot more expensive - Only work in a vacuum - Specimens have to be dead (as it is being used in a vacuum) - Images generally are only in black and white
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Whcih type of microscope is used to observe plant and animal cells?
Light microscope
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Which microscope uses a glass lens for focusing?
Light microscope
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What type of microscope is used to observe cell organelles and 3D objects
Electron microscope
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Which microscope uses electromagnets to focus the image?
Electron microscope
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Which microscope uses the human lens as a detection source?
Light microscope
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Which microscope uses a fluorescent screen as a detection source?
Electron microscope
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What is the correlation between wavelength and the size of the organelle?
If the organelle is smaller than half the wavelength of light then it can't be seen under the microscope
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Which microscope gives a higher resolution? Why?
Electron microscope- An electron beam has a shorter wavelength than a light beam
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Which microscope could be used to look at single organelles?
Electron microscope
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What is the maximum useful magnification for a light microscope?
x1500
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What is the maximum useful magnification for an electron microscope?
x15 000 00
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How many mm is 1 micrometre?
0.001mm
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What does TEM stand for?
Transmission Electron Microscope
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What does SEM stand for?
Scanning Electron Microscope
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How does a TEM work?
They use electromagnets to focus a beam of electrons, which is then transmitted through the specimen
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How does an SEM work?
They scan a beam of electrons across the specimen, which knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image
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What is an advantage of using a TEM microscope?
They give high resolution images that can show single organelles
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What is a disadvantages of using a TEM microscope?
They can only be used on thin specimens
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What is an advantage of SEM microscopes?
They can be used with thick specimens
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What is a disadvantage of using an SEM microscope?
They give lower resolution images than TEMs
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What is a temporary mount?
The prepared slide put under the microscope
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What is cell fractionation?
The process by which cells are broken up and their contents separated out
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What are the three main stages, in order, of cell fractionation?
- Homogenisation - Filtration - Ultracentrifugation
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What occurs during homogenisation?
The tissue is broken up and the cell membranes are broken to release the organelles using a homogeniser or blender. This is done in certain conditions.
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What three conditions does homogenisation have to be done in?
- Cold - Maintained pH - Isotonic
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Why do these conditions have to be maintained during homogenisation?
- The homogenate has to prevent the activity of enzymes in organelles that could break it down - It has to be isotonic to prevent damage to the cells through osmosis - A buffer solution should be added to maintain a pH as nay change in pH could alter
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the structure of the organelles or the function of the enzymes in the organelles
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Why is the homogenate solution then filtered through a gauze?
To separate any large cell debris, like connective tissue, from the organelles. As the organelles are much smaller than the debris they pass through the gauze.
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What is homogenate?
The fluid mixture of organelles left after homogenisation
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What is ultracentrifugation?
The process by which fragments in the filtered homogenate are separated out in a centrifuge
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How is ultracentrifugation carried out?
The homogenate is placed in a test tube that is put into a centrifuge. The test tubes arer spun at low speed, then the supernatant is removed, leaving behind a pellet of organelles, and this supernatant is spun again in a centrifuge but at a higher
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-->
--> speed, this process is repeated until all the desired organelles are collected in pellets at the bottom of the test tubes
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How are different organelles separated out?
The higher the speed of the centrifuge the lighter organelles that can be collected. E.g. Nuclei can be collected first as they are the heaviest organelle, leaving a pellet of nuceli at the bottom of the tube, then the supernatant can be spun again
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-->
--> at a higher speed to filter out the mitochondria, and so on
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What is the supernatant
The liquid at the top of the tube, in which the organelles are mixed in and spun in in the centrifuge
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Order these organelles from densest to least dense: Chloroplasts, Lysosomes, nuclei, ER, mitochondria, ribosomes
Nuclei, Chloroplasts, Mitochondria, Lysosomes, ER, Ribosomes
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