Studying cells Flashcards
What is magnification?
The process of enlarging the physical appearance/ image of something.
What is resolution?
The ability to distinguish between two points as separate structures.
Advantages of an optical microscope?
Preparation of slides are not complex, images can be seen in colour, ability to view live specimens.
Disadvantages of an optical microscope?
Low maximum magnification of X1500, low resolution as the wavelength of light is too long.
What are the two types of electron microscope and how do they function?
Transmission electron microscope-> electrons pass through and around sample, creating a 2D image. Scanning electron microscope-> electrons reflect off of the sample to show outside of cell in 3D image.
Advantages of a TEM?
High resolution of 0.5nm as wavelength of electrons are short, great magnification of X500,000
What is the equation for magnification?
image size/actual size
Disadvantages of TEM?
Could be artefacts on samples, images cannot be seen in colour, complex slide preparation, cannot view live samples.
Advantages of SEM?
High resolution of 3*-10 as wavelength of electrons is short, great magnification of X100,000
What is cell fractionation?
Breaking up cells and separating out organelles
What is cell fractionation used for?
Help study organelle structure and function.
What are the stages of cell fractionation?
Homogenisation and ultracentrifugation
Describe homogenisation.
Breaking up cells from tissue sample. Place in cold, isotonic, buffered solution. Blend cells in homogeniser to form homogenate which contains organelles. Filter homogenate to remove whole cells and debris.
Why are tissue samples placed in a cold, isotonic, buffered solution?
Cold->reduce enzyme activity so organelles aren’t broken down.
Isotonic->maintains water concentration to prevent shrinkage or lysis due to osmotic changes.
Buffered->maintains a constant pH to stop enzymes or proteins from denaturing.
Describe ultracentrifugation.
Spin test tube filled with filtered homogenate in centrifuge. A pellet of organelles and supernatant will be formed. Remove the supernatant to spin again at a slighter higher speed. Repeat again until the desired pellet of organelles is obtained.
