3.2.1.3 Methods of Studying Cells Flashcards
The 2 main categories for microscopes are…and…
Optical
Electron
The 2 main types of electron microscopes are… and…
Scanning
Transmission
True or false, you can view living specimen with electron microscopes
False
(You can only view non- living specimen however you can view living specimen with the optical microscope)
The 2 types of microscope that produce a 2D image of the specimen are the…and…microscope
Optical
Transmission
(Think Oti is 2D)
The …microscope produces a 3D image of the specimen
Scanning electron microscope
Sometimes when you are looking at a prepared sample under the microscope you can see things that aren’t actually part of the specimen e.g dust/ air bubbles/ fingerprints. These are known as…
Artefacts
Artefacts occur during the…of the sample
Preparation
The occurrence of artefacts can be decreased by more…preparation of the sample
Careful
Artefacts are common in the…microscope due to the lengthy treatment required to prepare samples
Transmission electron
Artefacts are common in the electron transmission microscope due to…
The lengthy treatment required to prepare samples
A longer wavelength leads to a …resolution
Lower
(Which is why optical microscopes have a lower resolution as the wavelength of light is relatively long)
Resolving power is the same thing as…
Resolution
Resolution is the same thing as…
Resolving power
An advantage of electron microscopes (both scanning and transmission) over optical microscopes is that they have a very powerful/ high…
Resolution
Under electron microscopes specimen can sometimes be seen in colour due to…colour
False
Resolution is the…distance that points can be separated and still be seen as…items
Smallest
Separate
On an optical microscope which is higher out of the coarse focus and fine focus
Coarse focus= above
Fine focus= below
(As C comes before F in alphabet)
As well as microscopy, another method of studying cells is…
Fractionation
(Isolating individual organelles within the cell to study)
As well as microscopy, another method of studying cells is…
Fractionation
(Isolating individual organelles within the cell to study)
Cell fractionation is the process where cells are…
Broken up (lysed) and the different organelles within the cells are released then separated out
Before cell fractionation can begin, the tissue is placed into a cold, buffered solution with the same water potential as the tissue known as the…
Isolation medium
The isolation medium is cold so that…
enzyme activity is kept low to prevent hydrolytic enzymes from damaging organelles
The isolation medium is cold to keep enzyme activity low and to prevent…enzymes from damaging organelles
Hydrolytic
The isolation medium is buffered to keep the…stable to prevent the enzymes and proteins from becoming denatured or damaged
pH
The isolation medium has the same water potential as the tissue to make sure that…
Water doesn’t leave or enter the organelles by osmosis so the organelles don’t swell or shrink
The first stage of fractionation is…, the second stage is…and the 3rd stage is…
Homogenisation
Filtration
Ultracentrifugation
Homogenisation breaks up the cells within the tissue to release the organelles from the cells and is done with a ….
Blender/ homogeniser
(Or pestle and mortar)
The fluid (‘soup’) obtained from homogenisation is called the…
Homogenate
In fractionation after homogenisation the homogenate (fluid (‘soup’) obtained is filtered to remove any…
Debris (whole cells or large bits of remaining tissue)
Ultracentrifugation is where the fragments (organelles) in the filtered homogenate are…
Separated in a centrifuge at increasing speeds (based on their size, mass and density)
…. centrifugation means repeating the process of centrifugation but increasing the speed each time
Differential
Centrifugation separates cell components based on … and…
Size
Density
In centrifugation the larger and denser components/ organelles form a…at the bottom of the tube
Pellet
In centrifugation, the smaller and less dense components/ organelles remain in suspension above the pellet (denser and larger components/ organelles) which is known as the…
Supernatant
The stage micrometer is used to c…the eyepiece graticule
Calibrate
Optical microscopes use…to form an image
Light
Electron microscopes (both scanning and transmission) use…to form an image
Beams of electrons
Which organelles can be viewed under an optical microscope
Nucleus, cell-surface membrane, cell wall, vacuole, chloroplasts
Cytoplasm (although not technically an organelle)
(Sometimes mitochondria can be seen but not always)
Which organelles can’t be viewed under an optical microscope as they’re too small
Ribosomes
Lysosomes
Endoplasmic reticulum
(These are the key ones but sometimes other organelles can’t be seen either)
What unit do we mostly use to measure plant and animal cells with
Micrometers
(Always convert to this when calculating the length of the cell unless the question says otherwise)
For transmission electron microscopes, what do darker parts of the image mean
The specimen is denser in this area so more electrons are absorbed and the image appears darker here
For an image produced by a transmission electron microscope, how can you tell which parts of the cell are denser
They’re darker as more electrons are absorbed
How were the first scientists to use electron microscopes able to distinguish between artefacts and organelles
They repeatedly prepared the specimen in different ways
If an object could be seen with one preparation technique but not another then it was more likely to be an artefact than an organelle
Resolution is…
The smallest distance that points can be separated and still be seen as separate items
Magnification is…
How much bigger the image is compared to the actual size of the object
A difference between optical microscopes and electron microscopes is that with…microscopes the image is viewed in colour but in… microscopes the image is viewed in black and white
Optical= colour
Electron (both transmission and scanning)= black and white
A difference between optical microscopes and electron microscopes is that …microscopes can be used to view living specimen but…microscopes can only be used to view non living specimen
Optical= living
Electron (both scanning and transmission)= non living (because the specimen is placed in a vacuum)
With electron microscopes (both transmission and scanning) you can only view non living specimen as the specimen is placed in a…
Vacuum
True or false, both optical microscopes, transmission electron microscopes and scanning electron microscopes need thin specimen
False
Scanning electron microscopes don’t require a thin specimen (but the other 2 do)
Which has a higher resolution out of TEMs or SEMS
TEMs
(But both types of electron microscopes still have a higher resolution than optical microscopes)
Which has a higher resolution out of TEMs or SEMS
TEMs
(But both types of electron microscopes still have a higher resolution than optical microscopes)
The tube containing the homogenate has been placed in the centrifuge at a low speed to form the pellet with the supernatant on top. Which out of the pellet and supernatant gets removed from the tube so that it can be placed at the centrifuge at an even higher speed than before
Supernatant
(The supernatant is drained off and poured into another tube to then be placed in the centrifuge at a faster speed so that the pellet containing the denser/ larger organelles stays in the tube)
When placing the homogenate in the centrifuge containing plant cells, what order would you expect the organelles to separate out in. (Remember, the first pellet formed contains the most dense and largest organelles)
Nuclei, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, ribosomes,
(Naughty Clever Monkeys Like Eating Raspberries)
Stages for preparing temporary mount for a piece of plant tissue
1) Use pipette to add one drop of water to the slide
2) Cut thin specimen of plant tissue using scalpel and place on top of water on slide
3) Add drop of potassium in potassium iodide to stain the starch granules blue/ black
4) Use a mounted needle to carefully lower the cover slip onto the specimen
When calibrating the eyepiece graticule using the stage micrometer, they both need to be at the same…
Objective lens power
