3.1: The methods of studying cells Flashcards by Amy O'Rourke

The cell is the basic unit of life.
However, with a few exceptions, cells are not visible to the naked eye and their structure is only apparent when seen under a microscope.
What are microscopes?

Microscopes are instruments that produce a magnified image of an object

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A simple what can act as a magnifying glass?

A simple convex glass lens can act as a magnifying glass

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A simple convex glass lens can act as a magnifying glass, but such lenses work more effectively if they are what?

A simple convex glass lens can act as a magnifying glass, but such lenses work more effectively if they are used in pairs in a compound light microscope

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The relatively long wavelength of light rays means that a light microscope can only distinguish between 2 objects if they are:
1. 0.2 μm
Or,
2. Further
apart

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A simple convex glass lens can act as a magnifying glass, but such lenses work more effectively if they are used in pairs in a compound light microscope.
The relatively long wavelength of light rays means that a light microscope can only distinguish between 2 objects if they are 0.2 μm, or further, apart.
This limitation can be overcome by using beams of electrons rather than beams of light.
With their shorter wavelengths, the beam of electrons in the electron microscope can do what?

With their shorter wavelengths, the beam of electrons in the electron microscope can distinguish between 2 objects only 0.1 nm apart

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The object

The object is the material that is put under a microscope

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The object is the material that is put under a microscope.

The image is what?

The image is the appearance of this material when viewed under the microscope

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The magnification of an object is what?

The magnification of an object is how many times bigger the image is when compared to the object

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The equation for magnification

The equation for magnification is:

Magnification = Image size ÷ Real size

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The important thing to remember when calculating the magnification is to ensure that what?

The important thing to remember when calculating the magnification is to ensure that the units of length are the same for both the:

Object
Image

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The resolution, or resolving power, of a microscope

The:
1. Resolution
Or,
2. Resolving power
,of a microscope is the minimum distance apart that 2 objects can be in order for them to appear as separate items

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Whatever the type of microscope, the resolving power depends on the:
1. Wavelength
Or,
2. Form of radiation used

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The resolution, or resolving power, of a microscope is the minimum distance apart that 2 objects can be in order for them to appear as separate items.
Whatever the type of microscope, the resolving power depends on the wavelength, or form of radiation used.
In a light microscope it is about 0.2 μm.
Greater resolution means what?

Greater resolution means greater clarity

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This means that the image produced is:

Clearer
More precise

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Increasing the magnification increases the size of an image, but does not always increase the resolution

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Every microscope has a limit of resolution

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The resolution, or resolving power, of a microscope is the minimum distance apart that 2 objects can be in order for them to appear as separate items.
Greater resolution means greater clarity.
This means that the image produced is clearer and more precise.
Increasing the magnification increases the size of an image, but does not always increase the resolution.
Every microscope has a limit of resolution.
Up to this point increasing the magnification will reveal more detail, but beyond this point increasing the magnification will not do this.
The object, while appearing larger, will just be what?

The object, while appearing larger, will just be more blurred

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In order to study the structure and function of the various organelles that make up cells, it is necessary to obtain large numbers of isolated organelles.
Cell fractionation is what?

Cell fractionation is the process where:

Cells are broken up
The different organelles they contain are separated out

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Before cell fractionation can begin, the cut up tissue is placed in a cold, buffered solution of the same water potential as the tissue

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In order to study the structure and function of the various organelles that make up cells, it is necessary to obtain large numbers of isolated organelles.
Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out.
Before cell fractionation can begin, the cut up tissue is placed in a cold, buffered solution of the same water potential as the tissue.
The solution is cold to do what?

The solution is cold to reduce enzyme activity that might break down the organelles

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The solution is of the same water potential as the tissue to prevent organelles:
1. Bursting
Or,
2. Shrinking
as a result of osmotic gain, or loss of water

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The solution is buffered so that the pH does not fluctuate

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Any change in pH could:
1. Alter the structure of the organelles
Or,
2. Affect the functioning of enzymes

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There are 2 stages to cell fractionation:

Homogenation
Ultracentrifugation

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Homogenation is when cells are broken up by a homogeniser (blender)

This releases the organelles from the cell

Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out. There are 2 stages to cell fractionation, homogenation and ultracentrifugation. Homogenation is when cells are broken up by a homogeniser (blender). This releases the organelles from the cell. The resultant fluid, known as what, is then what?

The resultant fluid, known as homogenate, is then filtered

Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out. There are 2 stages to cell fractionation, homogenation and ultracentrifugation. Homogenation is when cells are broken up by a homogeniser (blender). This releases the organelles from the cell. The resultant fluid, known as homogenate, is then filtered to do what?

The resultant fluid, known as homogenate, is then filtered to remove any: 1. Complete cells 2. Large pieces of debris

Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out. There are 2 stages to cell fractionation, homogenation and ultracentrifugation. Homogenation is when cells are broken up by a homogeniser (blender). Ultracentrifugation is the process by which what?

Ultracentrifugation is the process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge

This spins tubes of homogenate at very high speed in order to create a centrifugal force

For animal cells, the process is as the tube of filtrate is: 1. Placed in the centrifuge 2. Spun at a slow speed

The heaviest organelles, the nuclei, are forced to the bottom of the tube

The heaviest organelles, the nuclei, are forced to the bottom of the tube, where they form a thin: 1. Sediment Or, 2. Pellet

The fluid at the top of the tube, supernatant, is removed

Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out. There are 2 stages to cell fractionation, homogenation and ultracentrifugation. Ultracentrifugation is the process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge. This spins tubes of homogenate at very high speed in order to create a centrifugal force. For animal cells, the process is as the tube of filtrate is placed in the centrifuge and spun at a slow speed. The heaviest organelles, the nuclei, are forced to the bottom of the tube, where they form a thin sediment, or pellet. The fluid at the top of the tube, supernatant, is removed, leaving just what?

The fluid at the top of the tube, supernatant, is removed, leaving just the sediment of nuclei

Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out. There are 2 stages to cell fractionation, homogenation and ultracentrifugation. Ultracentrifugation is the process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge. This spins tubes of homogenate at very high speed in order to create a centrifugal force. For animal cells, the process is as the tube of filtrate is placed in the centrifuge and spun at a slow speed. The heaviest organelles, the nuclei, are forced to the bottom of the tube, where they form a thin sediment, or pellet. The fluid at the top of the tube, supernatant, is removed, leaving just the sediment of nuclei. The supernatant is what?

The supernatant is: 1. Transferred to another tube 2. Spun in the centrifuge at a faster speed than before

Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out. There are 2 stages to cell fractionation, homogenation and ultracentrifugation. Ultracentrifugation is the process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge. This spins tubes of homogenate at very high speed in order to create a centrifugal force. For animal cells, the process is as the tube of filtrate is placed in the centrifuge and spun at a slow speed. The heaviest organelles, the nuclei, are forced to the bottom of the tube, where they form a thin sediment, or pellet. The fluid at the top of the tube, supernatant, is removed, leaving just the sediment of nuclei. The supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before. The next heaviest organelles, the what, are what?

The next heaviest organelles, the mitochondria, are forced to the bottom of the tube

Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out. There are 2 stages to cell fractionation, homogenation and ultracentrifugation. Ultracentrifugation is the process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge. This spins tubes of homogenate at very high speed in order to create a centrifugal force. For animal cells, the process is as the tube of filtrate is placed in the centrifuge and spun at a slow speed. The heaviest organelles, the nuclei, are forced to the bottom of the tube, where they form a thin sediment, or pellet. The fluid at the top of the tube, supernatant, is removed, leaving just the sediment of nuclei. The supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before. The next heaviest organelles, the mitochondria, are forced to the bottom of the tube. The process is continued in this way so that, what?

The process is continued in this way so that, at each increase in speed, the next heaviest organelle is: 1. Sedimented 2. Separated out

An example of low speed in an ultracentrifuge is what?

An example of low speed in an ultracentrifuge is 1,000 x Gravity

An example of medium speed in an ultracentrifuge is what?

An example of medium speed in an ultracentrifuge is 3,500 x Gravity

An example of high speed in an ultracentrifuge is what?

An example of high speed in an ultracentrifuge is 16,500 x Gravity

The organelles to be separated out when the speed of centrifugation is 1,000 is what?

The organelles to be separated out when the speed of centrifugation is 1,000 is the nuclei

The organelles to be separated out when the speed of centrifugation is 3,500 is what?

The organelles to be separated out when the speed of centrifugation is 3,500 is the mitochondria

The organelles to be separated out when the speed of centrifugation is 16,500 is what?

The organelles to be separated out when the speed of centrifugation is 16,500 is the lysosomes

The techniques of cell fractionation and ultracentrifugation enabled what?

The techniques of: 1. Cell fractionation 2. Ultracentrifugation enabled considerable advances in biological knowledge

The techniques of cell fractionation and ultracentrifugation enabled considerable advances in biological knowledge. They allowed a detailed study of what?

The techniques of cell fractionation and ultracentrifugation allowed a detailed study of the: 1. Structure 2. Function of organelles

The techniques of cell fractionation and ultracentrifugation enabled considerable advances in biological knowledge. They allowed a detailed study of the structure and function of organelles, by showing what?

The techniques of cell fractionation and ultracentrifugation allowed a detailed study of the: 1. Structure 2. Function of organelles, by showing what isolated components do

The solution used during cell fractionation prevents what bursting or shrinking as a result of osmotic gain or loss of water?

The solution used during cell fractionation prevents organelles: 1. Bursting Or, 2. Shrinking as a result of osmotic gain or loss of water

The solution used during cell fractionation prevents organelles bursting or shrinking as a result of osmotic gain or loss of water, not what?

The solution used during cell fractionation prevents organelles: 1. Bursting Or, 2. Shrinking as a result of osmotic gain or loss of water, not cells

Why do we need microscopes?

We need microscopes to enable us to see microscopic: 1. Organisms 2. Cells

We need microscopes to enable us to see microscopic organisms and cells. For example, a pin head is how small?

For example, a pin head is 2mm

We need microscopes to enable us to see microscopic organisms and cells. For example, a pin head is 2mm. Pollen is how small?

Pollen is 20 µm

We need microscopes to enable us to see microscopic organisms and cells. For example, a pin head is 2mm. Pollen is 20 µm. A lymphocyte is how small?

A lymphocyte is 4 µm

``` We need microscopes to enable us to see microscopic organisms and cells. For example, a pin head is 2mm. Pollen is 20 µm. A lymphocyte is 4 µm. A red blood cell is how small? ```

A red blood cell is 2 µm

``` We need microscopes to enable us to see microscopic organisms and cells. For example, a pin head is 2mm. Pollen is 20 µm. A lymphocyte is 4 µm. A red blood cell is 2 µm. The Ebola virus is how small? ```

The Ebola virus is 200 nm

Sectioning

``` Sectioning is cutting a piece of the specimen thin enough to allow: 1. Light Or, 2. Electrons to pass through ```

Fixing

Fixing is adding chemicals to the specimen to stop it from changing

With light (optical) microscopes, the specimens can be what?

With light (optical) microscopes, the specimens can be alive

With light (optical) microscopes, what can be used to aid vision?

With light (optical) microscopes, dyes can be used to aid vision

Electron microscopes generally cost more than what?

Electron microscopes generally cost more than £20,000

The specimens being observed on a transmission electron microscope (TEM) are called what?

The specimens being observed on a transmission electron microscope (TEM) are called sections

The specimens being observed on a transmission electron microscope (TEM) are called sections. The sections need to be what to allow electrons to pass through?

The sections need to be thin to allow electrons to pass through

The specimens being observed on a transmission electron microscope (TEM) are called sections. The sections need to be thin to allow electrons to pass through. The individual sections are placed where?

The individual sections are placed in a vacuum

The individual sections are placed in a vacuum, because air molecules deflect electrons

Property - Maximum resolving power: | For light microscopes, what is the maximum resolving power?

For light microscopes, the maximum resolving power is 200 nm

Property - Maximum resolving power: | For light microscopes, the maximum resolving power is 200 nm, limited by what?

For light microscopes, the maximum resolving power is 200 nm, limited by the wavelength of light

Property - Maximum resolving power: For light microscopes, the maximum resolving power is 200 nm, limited by the wavelength of light. What is the maximum resolving power of electron microscopes?

The maximum resolving power of electron microscopes is 2 nm

Property - Magnification: | For light microscopes, what is the magnification?

For light microscopes, the magnification is up to x2,000

Property - Magnification: | For light microscopes, the magnification is up to x2,000, whereas for electron microscopes, the magnification is what?

For: 1. Light microscopes, the magnification is up to x2,000 ,whereas 2. Electron microscopes, the magnification is up to x2,000,000 depending on the type

Property - Specimens: | With light microscopes, what can be observed directly?

With light microscopes, living specimens can be observed directly

Property - Specimens: | With light microscopes, living specimens can be observed directly and what are easily prepared?

With light microscopes: 1. Living specimens can be observed directly 2. Thin sections of tissue are easily prepared

Property - Specimens: With light microscopes, living specimens can be observed directly and thin sections of tissue are easily prepared. With electron microscopes, specimens must be what?

With electron microscopes, specimens must be dead

Property - Specimens: With light microscopes, living specimens can be observed directly and thin sections of tissue are easily prepared. With electron microscopes, specimens must be dead and viewed how?

With electron microscopes, specimens must be: 1. Dead 2. Viewed in a vacuum

With electron microscopes: 1. Specimens must be dead and viewed in a vacuum 2. A harsh preliminary treatment is needed

With electron microscopes: 1. Specimens must be dead and viewed in a vacuum 2. A harsh preliminary treatment is needed, which may cause distortions and artefacts

Property - Image: | With light microscopes, staining is what?

With light microscopes, staining is not always necessary

Property - Image: | With light microscopes, staining is not always necessary, so what?

With light microscopes, staining is not always necessary, so real colours can be observed

Property - Image: With light microscopes, staining is not always necessary, so real colours can be observed. The staining of what allows colour images?

The staining of thin sections allows colour images

With electron microscopes, staining using metal dyes is always necessary

Property - Image: With light microscopes, staining is not always necessary, so real colours can be observed. The staining of thin sections allows colour images. With electron microscopes, staining using metal dyes is always necessary and the images are what?

With electron microscopes: 1. Staining using metal dyes is always necessary 2. The images are black and white

With electron microscopes: 1. Staining using metal dyes is always necessary 2. The images are black and white (false colours may be added later by photographic techniques)

Property - Cost: | Light microscopes are within the budget of what?

Light microscopes are within the budget of: 1. Individuals 2. Schools

Property - Cost: Light microscopes are within the budget of individuals and schools, whereas electron microscopes are within the budget of what?

Light microscopes are within the budget of individuals and schools, whereas electron microscopes are within the budget of: 1. Universities 2. Research laboratories only

The result of a TEM is a flat, 2D image. | To get a 3D image, you must do what?

To get a 3D image, you must cut a series of sections to build up the image