Analysis Of Cell Components Flashcards
Why is magnification?
It’s how much bigger the image is than the specimen
What is resolution?
- it’s how detailed the image is
- it’s also how well a microscope distinguishes between two points that are close together
- if a microscope can’t separate two objects increasing magnification won’t help
What is an optical light microscope?
- they use light to form an image
- they have a maximum resolution of 0.2 micrometers
What is an electron microscope?
- electrons are used to form images
- they have a higher resolution than optical microscopes so are more detailed
- they have a maximum resolution of 0.0002 micrometers
- maximum magnification is x1,500,000
What is a transmutation electron microscope?
- TEM uses electromagnets to foci ur beams of electrons which is transmitted through a specimen
- denser parts of specimen absorb more electrons which make them look darker on the end image
- TEM have high resolutions
How does a scanning electron microscope work?
- SEM scans a beam of electrons across a specimen
- the beam of electrons knocks off electrons from the specimen which see gathered in the cathode ray tube to form an image
What is the first stage of preparing a temporary mount of a specimen on a slide?
- Pipette a small drop of water onto the slide
- use tweezers to place a thin section of your specimen on top of the water drop
What is Homogenisation?
vibrate the cells or grind the cells up in a blender to break up the plasma membrane and release organelles into the solution
What is filtration?
- the homogenised cell solution is filtered through a gauze to separate any large cell debris or tissue debris like connective tissue from the organelles
- the organelles are smaller than the debris so pass through the gauze
What is ultracentrifugation?
- After filtration you are left with a solution with a mixture of organelles
- use ultracentrifugation to separate a particular organelle from the others
What is the first stage of ultracentrifugation?
- The cell fragments are poured into a tube which is put into a centrifuge and spun at a low speed
- the heaviest organelles (nuclei) get flung to the bottom by the centrifuge
- they form a thick sediment at the bottom called a pellet the other organelle stay suspended in the fluid above called the supernatant
What is the second stage of ultracentrifugation?
- The supernatant is drained off, poured into another tube and spun in the centrifuge at a higher speed
- the heaviest organelles (mitochondria) forms a pellet at the bottom of the tube
- the supernatant is drained off and spun in the centrifuge at an even higher speed
What is the third stage of ultracentrifugation?
- This process is repeated at higher and higher speeds until all the organelles are separated out
- each time the pellet is made up of lighter and lighter organelles
What can you see with an optical microscope?
- you can barely make out mitochondria
- you can see the nucleus
What can’t you see with an optical microscope?
- ribosomes
- lysosomes
- endoplasmic reticulum
What can you see with TEM microscopes?
- The internal structure of organelles like chloroplasts
- they can only be used on thin specimens
What is the second stage of preparing a temporary mount of a specimen on a slide?
-add a drop of stain which highlights objects in the cell
What stains are used in preparing a slide?
- eosin is used to make cytoplasm show up
- iodine in potassium iodine is used to stain starch grains in plant cells
What is the third stage of preparing a temporary mount of a specimen on a slide?
- add a cover slip
- stand the slip upright on the slide next to the water droplet
- carefully tilt and lower it onto the specimen
- don’t let any air bubbles in
What is a coverslip?
A small square of plastic that protects the specimen
How should the solution be kept for homogenisation?
- The solution much be kept ice cold to reduce the activity of enzymes which break down organelles
- the solution should be kept isotonic to prevent damage to the organelles through osmosis
- a buffer solution should be added to maintain pH
What does isotonic mean?
A solution with the same concentration of chemicals as the cells being broken down
