Cell structure

Microscopes 

Light microscopes

max res= 0.2 micrometers

max magnification= x1500

Laser Scanning Confocal 

laser beam is focused through lens that is then split by a beam splitter, which causes some light to be directed on to the specimen. that laser forces the dyes to give off fluorescent light which is focused through a pinhole onto a detector. thsi then produces a image on a computer.

these can be used to at different depths of objects and can generate a 3D image.

TEM

use electromagnets to focus beam of electrons onto specimen. produces 2D images- denser part absorb more electrons. used to look at very small organelles+ internal structure. Have to be cut very thin.

max res=0.0002 micrometers

max magnification=x1000000

SEM

scan beam of electrons across specimen. this knocks of electrons which are collected in a cathode ray tube to form a 3D image

max res=0.002 micrometers

max magnification=x500000

Slide preparation

dry mount-cut specimen thinly use tweezer to put onn slide then cover with cover slip

wet mount- pipette a drop of water on slide and put specimen on top. put cover slip upright next to water then slowly lower over specimen. if want to add stain, then put a drop next to cover slip and put paper towel on oppsoite side and stain will be drawn under.

Setting up light microscope

1. clip slide onto stage

2. select lowest power objective lens

3. use coarse adjustment knob to move objective lens down

4. adjust focus with fine adjustment lens until you have clear image

Eyepiece graticule- fitted on eyepiece, is like a ruler with no units

Stage micrometer- placed on stage, microscope slide with scale, used to work out value of divisions on eyepiece at a particular magnification

Staining

stain is taken up some parts more than others…