Biology The Microscope. May 20 1:19 PM. Using a Microscope to Explore the Cell

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Oswin Brown
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1 Biology The Microscope Using a Microscope to Explore the Cell Resolution or Resolving power The ability of the eye, or other instrument, to distinguish between two objects that are close together High resolution Low resolution 1

Early Use of Microscopes Tendency to look at the known

microscopes had 2 lenses doubling the distortion of the

in is single lens scopes achieve magnifications as high

2 Early Use of Microscopes Tendency to look at the known world Magnified up to 50x the actual size Most microscopes had 2 lenses doubling the distortion of the poor quality lenses Van Leeuwenhoek mastered lens craft in is single lens scopes achieve magnifications as high as 500x with little distortion Van Leeuwenhoek s microscope 2

3 Types of Microscopes: Light microscopes Uses light to view a specimen Include simple (one lens) and compound (more than one lens) Can see most but not all cells, and cell structures Resolution limited to about 0.2 µm Resolving power is limiting, so the light source must be changed to accommodate this Types of Microscopes (cont ) Electron microscopes Very high magnifications Very expensive Use a beam of electrons instead of light to magnify objects Use electromagnets to focus beams instead of lenses 3

Modern Light Microscopes Compound light microscopes today have drastically improved how we see the world New glassmaking technology has removed the distortions from lenses,

4 Modern Light Microscopes Compound light microscopes today have drastically improved how we see the world New glassmaking technology has removed the distortions from lenses, allowing scientists to focus more sharply on the images they were observing Magnifications up to 5000x Resolutions as fine as mm Compound Light Microscope Parts Condenser lens 4

5 The Compound Microscope The modern compound light microscope usually has two lenses; one in the eyepiece and one or more objective lenses Parts: eyepiece contains the ocular lens. Usually magnifies 10x Parts of a compound light microscope (cont ) body tube separates the eyepiece and objective lenses and keeps them in place revolving nose piece holds the objective lenses and allows them to be changed objectives lenses help magnify the object. Low power 4x Medium power 10x High power 40x 5

6 Parts of a compound light microscope (cont ) Stage a platform to hold the slide Coarse adjustment knob helps to focus the object. Used under low power Fine adjustment knob helps focus the object. Used under medium and high powers Parts of a compound light microscope (cont ) Arm connects body tube and base. Allows for transport of the microscope Condenser lens directs light into the object Diaphragm controls the amount of light that goes through the slide Light source provide light to view the specimen Base supports the microscope 6

7 Plant parasitic nematode DIC Epithelial cell in anaphase Confocal Microscope 7

Polychaete nematode Darkfield 2 Types Electron Microscopes

built in 1938 at U of Toronto achieving magnifications of

8 Polychaete nematode Darkfield 2 Types Electron Microscopes Transmission electron microscope (TEM) Magnifications up 750,000 times Resolutions as low as µm Electrons are transmitted through the specimen First built in 1938 at U of Toronto achieving magnifications of 7000X First observed cell structures See page 20 for figure Mitochondrion Rough ER notice the ribosomes 8

Mitochondrial DNA and RNA Scanning Electron Microscope

005 µm lower than TEM Specimen is sprayed with a gold

electron detector produces a 3 dimensional image of the

9 Mitochondrial DNA and RNA Scanning Electron Microscope (SEM) Magnification s over 500,000 times Resolutions µm lower than TEM Specimen is sprayed with a gold coating and scanned with a narrow beam of electrons An electron detector produces a 3 dimensional image of the specimen on a TV screen See page 20 for figure Sea urchin sperm Diatom 9

10 Mitochondria in human liver cell 10

STRUCTURE OF THE MICROSCOPE

STRUCTURE OF THE MICROSCOPE Use the word list to label the microscope below: Light Source Coarse adjustment knob Diaphragm Stage Clips Objectives Fine Adjustment Knob Base Stage Stage Clips Arm Revolving