AS Biology Unit 1 - Cells and movement in and out of them

HideShow resource information
What is the material that is put under the microscope referred to as?
The object
1 of 23
What is the appearance of the object when viewed under a microscope called?
The image
2 of 23
What is magnification?
How many times bigger the image is when compared to the object
3 of 23
How do you work out magnification?
Size of image DIVIDED by size of object
4 of 23
Using manification, what is the equation to work out the size of the object?
Size of image DIVIDED by manification
5 of 23
What is important to remember when completing calculations around manifications?
That all the units are the same
6 of 23
What is resolution?
Minimum distance apart that two objects can be in order to appear seperate objects
7 of 23
What does resolution depend on?
The wavelength or form of radiation used
8 of 23
What will increasing the manification do?
Increase the size of the image but not always the resolution
9 of 23
What is the process where cells are broken up and the different organelles they contain are seperate out
Cell fractionation
10 of 23
What must happen to the tissue before cell fractionation?
It must be placed in a cold isotonic buffer solution
11 of 23
What does the cold, isotonic buffer solution do?
Cold - reduce enzyme activity that might break down organelles, isotonic - prevent organelles bursting or shrinking due to osmotic gain or loss of water (isotonic solution has same water potential as tissue) buffered - maintain constant pH
12 of 23
What is Homogenation?
Cells are broken up by a homogeniser (blender) which releases organelles from the cells
13 of 23
What is Ultracentrifugation?
Process by which the fragments in the filtered homogenate are sperated in machine called a ultracentrifuge
14 of 23
Explain the process of Ultracentrifugation
The tube of filtrate is placed in the untracentrifuge and spun at low speed, the heaviest organelles are forced to the bottom where they form a thin sediment, the supernatant (lightests) are transfered to another tube and that is spun again faster
15 of 23
Name the order of the heaviest organelles to the lightest in an animal cell
Heaviest - Nuclei, Mitochondria, Lysosome and Ribsosomes
16 of 23
Why do light microscopes have a poor resolution?
As they have long wavelengths of light
17 of 23
Name the two advantages of an electron microscope
Electron beam has a very short wavelength so has high resolution, electrons are negatively charged so can be focused using electromagnets
18 of 23
Name the two types of electron microscopes
TEM - Transmission electron microscope and SEM - Scanning electron microscope
19 of 23
Describe how a TEM works
Trasmission electron microscope - Electron beam passes trhough object which absorbs electrons and appears dark, other parts allow them to pass through so appear light
20 of 23
What are the limitations for a TEM?
Object cannot be living as has to be in a vacuum, image only in black and white due to staining, object must be thin to allow electrons through, images only in 2D
21 of 23
Describe how a SEM works
It directs a beam of electrons onto surface of object from above, the beam is then passed back and forth scanning the object and creating a 3D image
22 of 23
What is the difference between TEM and SEM in terms of resolution?
SEM has a lower resolution than TEM but still higher than a light microscope
23 of 23

Other cards in this set

Card 2

Front

What is the appearance of the object when viewed under a microscope called?

Back

The image

Card 3

Front

What is magnification?

Back

Preview of the front of card 3

Card 4

Front

How do you work out magnification?

Back

Preview of the front of card 4

Card 5

Front

Using manification, what is the equation to work out the size of the object?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »