Microscopes

light microscope

• light passed through

• focussed by glass lenses

• image formed on human retina

• max magnification - 1000x

• resolution - 0.2 mm

• Measure living cells

confocal fluorescence microscope

• multicolor straining

• labeling of structures within cells

• measurement of the physiological state of a cell

• studying the dynamic behavior exhibited in live-cell imaging

• Maximum Magnification: 2000x

• Resolution: 250 nm

• Both living and dead cells

Transmission electron microscope

• Electrons passed through specimen

• Focused by magnetic lenses

• Image formed on fluorescent screen like TV screen

• Image is then photographed

• Maximum Magnification: 1 000 000’s x

• Resolution: 0.00002 mm

• Dead cells

scanning electron microscope

• Specimen sprayed with thin coat of metal

• Electron beam scanned across surface of specimen

• Metal emits secondary electrons.

• Emitted electrons focused by magnetic lenses

• Image formed on fluorescent screen like TV screen

• Image is then photographed

• Maximum Magnification: 10 – 3 000 000 x

• Resolution: 1 – 20 nm

• Dead cells

scanning probe microscope

• sharp probes that are passed over the surface of the specimen and interact with it directly

• Maximum Magnification: 100–100 000 000x or more

• Resolution: 100 nm

• Living and dead cells

light microscope parts

• objective

• specimen

• condenser lens

• light source

magnifiaction

• how many times bigger the image of specimen is compared to actual size

• decreas in field of view, increase in magnification

light microscope magnification

• ocular lens (eyepiece) (often has magnifcation of 10x)

• objective lens (series of usually 3 objective lenses with different magnifications)

magnification formula

• M = I/A

• magnification = image size/actual size

• magnification = (ocular) x (objective)

measurements

1 m = 1000 mm (millimeter)

1 mm = 1000 µm (micrometer)

1 µm = 1000 nm (nanometer)

resolution

ability to distinguish between two seperate points (if cannot be ressolved, observed as one point)

light microscope resolution

• low resolution

• limited by wavelength of light

• light passing through specimen diffracts

• longer wavelength, more light diffracted, more overlap as points get closer

electron microscope resolution

• high resolution

• electrons have small wavelengths

• be closer before diffracted beams overlap

light vs electron microscope

• light is simple but has less resolution and magnification

• electron is complicated but has high resolution and magnification

straining

• penetrate cell walls and highlight cell components

• distinguish live and dead cells

• count number of cells of a particular type in a certain biomass

totipotent stem cell

differenciate into any cell type, including any that make up embryo or placenta

pluripotent embryo stem cell

differentiate into any cell type in developing embryo but not into stem cell that make placenta

multipotent adult stem cell

differenciate into a limited range of cell types

cell research

• cell therapy

• cure diseases

• grow human embryos

• repair damaged organs

• differenciate into specialized cells