Viruses, Microscopes And Cell Fractionation Flashcards
1
Q
Viruses are…..?
A
- acellular
- non-living
2
Q
Virus Structure?
A
- genetic material
- capsid
- attachment protein
3
Q
Types of Microscopes and how resolution is determined?
A
- Optical (light) microscope - resolution determined by wavelength of light
- Transmission electron microscope and Scanning Electron Microscope - resolution determined by wavelength of beam of electrons
4
Q
What is Magnification?
A
How many times larger an image is compared to the object
5
Q
What is Resolution?
A
Minimum distance between two objects in which they are still viewed as separate
6
Q
Characteristics of Optical Microscopes?
A
- beam of light condensed to create image
- poorer resolution due to longer wavelength
- lower magnification
- colour images
- can view living samples
7
Q
Characteristics of Electron Microscopes?
A
- beam of electrons condensed to create image - beam condensed by electromagnets
- higher resolution due to shorter wavelength
- higher magnification
- black and white images
- must be non-living
8
Q
Image Size, Actual Size and Magnification Equation
A
- Image size = Actual Size x Magnification (I=AM)
- Actual Size = Image Size/Magnification (A=I/M)
- Magnification = Image Size/Actual Size (M=I/A)
9
Q
What is the Eye Piece Graticule?
A
- Inside optical microscope
- scale on glass disc
- measures size of objects under microscope
10
Q
Cell Fractionation Key Points?
A
- Isolate different organelles to be studied
- enables individual organelle structure and function to be studied
- cells broken open to release contents and organelles then separated
11
Q
Why must cells be prepared in cold, isotonic and buffered solution?
A
- Cold - reduced enzyme activity
- Isotonic - same water potential to prevent osmosis as it could lead to cell shrivel or burst
- Buffered - solution has pH buffer to prevent damage to organelles
12
Q
Two steps of cell Fractionation?
A
- Homogenisation
- Ultracentrifugation
13
Q
What is Homogenisation?
A
- Cells broken open (homogenised) in blender - blended in cold, isotonic and buffered solution
14
Q
What is Ultracentrifugation?
A
- Filtered solution spun at different speeds in centrifuge
- Organelles separate according to their densities
15
Q
Differential Centrifugation?
A
- Low speed to high speeds
- Each time the supernatant (liquid) is removed, leaves behind a pellet of organelle
- Nucleus 2. Chloroplasts (if plant tissue) 3. Mitochondria 4. Lysosomes 5. ER 6. Ribosomes
