A Tour of the Cell Prokaryote No membrane bound nucleus or organelles DNA is concentrated in a region called the nucleoid 1 – 10 μm in diameter Include bacteria and archaea Eukaryote Membrane-bound organelles True nucleus (w/DNA) enclosed in a nuclear envelope 10 – 100 μm in diameter Include protists, plants, fungi and animal cells
Microscopes Transmission Electron Microscope (TEM) Scanning Electron Microscope (SEM)
The Compound Light Microscope Magnifies up to 1500x Living and non-living specimens 3-D image Image produced using 2 lenses Light must be able to pass through specimen
Parts of the Microscope Objectives Left- Scanning- 4x Middle-Low power-10x Right-High power-40x
Magnification - the ratio of an object’s image to its real size Total magnification = eyepiece x objective X
Resolving Power The ability of a microscope to distinguish clearly between objects close together under a microscope Low resolution High resolution
Field of Vision Amount of area visible under each objective
Measuring the field of vision 1 millimeter (mm) = 1000 micrometer (μm) How large is the field of vision pictured in mm? In μm? Suppose you estimate 13 microorganisms could fit across this field of vision? How large is one microorganism in μm?
Field of Vision Observe the next three slides. What is happening to the field of vision as the magnification increases?
What happened to the field of vision as you change from scanning to low to high power objective? How would the object’s apparent size change?
The Stereoscope Also called dissecting microscope Can view large opaque objects Living and non-living specimens Magnifies up to 100x 3-D image
Electron Microscopes Electron Microscopes – Electron beam focused through the specimen or onto its surface (electron beams have wavelengths much shorter than visible light) Two types –Transmission Electron Microscope (TEM) – internal or ultrastructure –Scanning Electron Microscope (SEM) – surface of the specimen –Scanning Tunneling Microscope (STM) - views molecules at atom level