Cells Flashcards
1
Q
Light microscopes?
A
- use light form an image
- max resolution = 0.2 micrometres
- can’t see organelles smaller than 0.2 e.g. ribosomes/the endoplasmic reticulum/lysosomes
- max useful magnification = x 16500
2
Q
Electron microscopes?
A
- use electrons to form an image
- more detailed image + more organelles
- max resolution = 0.0002 micrometres
- max useful magnification = x 1,500,000
- black and yt images produced
3
Q
Transmission electron microscopes (TEMs)?
A
- use electromagnets to focus beam of electron -> transmitted thru specimen
- denser parts of specimen absorb more electron so - look darker on image
- can only view in a vacuum so - no good for living organisms
4
Q
Scanning electron microscopes (SEMs)
A
- scan a beam of electrons across specimen - knocks off electrons from specimen -> electrons gathered in cathode ray tube - to form image
- image show surface of specimen
5
Q
Advantages of TEMs v SEMs
A
TEMs: give high resolution images so - shows small objects
SEMs: can be used on thick specimens
- can be 3D
6
Q
Disadvantages of of TEMs v SEMs
A
TEMs: only used on thin specimens
- only used on non-living specimens
SEMs: give lower resolution images than TEMs
- only used on non-living specimens
7
Q
Steps for preparing microscope slides?
A
- pipette small drop of water onto centre of slide
- use tweezers to place a thin section of your specimen on top of the water drop aka ‘temporary/wet mount’ (specimen needs to let light through to be able to see it clearly)
- Add a. drop of a stain. (used to highlight objects in a cell)
- add the cover slip (protects the specimen) - stand slip upright on the slide, next to the water droplet -> carefully tilt and lower it so it covers the specimen (no air bubbles under there - obstruct view of the specimen)
8
Q
Endomembrane system/organelles working together?
A
- mRNA copy of instructions (gene) for protein is made in nucleus
- mRNA leaves nucleus thru a nuclear pore
- mRNA attaches to a ribosome (attached to ER) - ribosome reads instructions to assemble protein
- protein molecules r pinched off in vesicles & travel towards Golgi apparatus
- vesicle fuses w Golgi apparatus
- apparatus processes & packages protein molecules ready for release
- packaged protein molecules r pinched off in vesicles from apparatus & move towards cell surface membrane
- vesicle fuses w cell surface membrane
- cell surface membrane opens to release protein molecules outside