Cells Flashcards
What is a microscope?
An instruments that produces a magnified image of an object
What type of lenses are in compound light microscopes?
Convex glass lenses
What is the resolution of most light microscopes?
0.2 micrometers
Which has a high resolution: light or electron microscopes?
Electron
Why do electron microscopes have higher resolutions than light microscopes?
Beams of electrons have shorter wavelengths than beams of light
What is magnification?
How many times bigger the image is compared the object.
Magnification = image size / object size
What is 1km in metres?
1 * 10^3 m
What is 1mm in metres?
1 * 10^-3 m
What is 1μm in metres?
1 * 10^-6 m
What is 1nm in metres?
1 * 10^-9m
What does μm stand for?
micrometre
What does nm stand for?
nanometre
What is meant by resolving power?
The ability of a microscope to distinguish between two close objects
What does the resolving power of a microscope depend on?
The wavelength and form of radiation used
What is meant by the resolution limit?
The point where increasing the magnification will not also increase the detail
What is Cell Fractionation?
The process in which cells are broken up into different organelles and the organelles are separated out
Why do we need cell fractionation?
So we can isolate organelles and study the structure and function of them
What are the features of the solution the sample placed in before cell fractionation?
Cold isotonic buffered solution
What are three properties of cell fractionation buffer solution and why?
- Cold to reduce enzyme activity that may break down organelles
- Same water potential as the sample to prevent organelles bursting/shrinking as a result of osmotic water gain/gain
- Buffered so the pH doesn’t fluctuate and alter organelle structure and/or functioning enzyme activity
What is meant by a buffer solution?
One that can resist pH change upon the addition of an acidic or basic components
What are the two steps to cell fractionation?
- Homogenation
- Ultracentrifugation
What is homogenation?
The process by which cells are broken up in a homogeniser, releasing organelles from the cell. The resultant fluid, the supernatant, is filtered to remove complete cells and debris
What is a homogenate?
The fluid left after a sample is put through a homogeniser
What is Ultracentrifugation?
Process by which the fragments in the filtered homogenate are separated in a centrifuge.