chapter 3: cell structuresection 1: looking at cells 1 cell structure chapter 3
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Chapter 3: Cell Structure Section 1: Looking at Cells
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Cell Structure
Chapter 3
Chapter 3: Cell Structure Section 1: Looking at Cells
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Objectives
• Relate magnification and resolution in the use of microscopes
• Analyze how light microscopes function.
• Compare light microscopes with electron microscopes.
• Describe the scanning tunneling microscope.
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Microscopes allow scientists to see what cannot be seen with the unaided eye.
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Properties of Images
Magnification
Resolution
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Magnification = the apparent increase in the size of the image
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Resolution = the increase in visible details
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Types of Microscopes
Compound light microscopes
Electron microscopes
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Microscopes
Compound light microscopes use
1. Light reflected off of or passing through an object to produce an enlarged image.
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
2. Two kinds of lenses
• Ocular lens—lens set nearest the viewer’s eye
• Objective lenses—lenses nearest the specimen
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Lens magnification is indicated by a number followed by X.
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Microscopes
Total Magnification
• Calculated by multiplying the magnifications of the ocular and objective lenses.
Ocular magnification ……………10Xx Objective magnification………….40X Total magnification……………...400X
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Light microscopes have limited use, practical magnification is limited to 1000X.
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Microscopes
Electron microscopes
–Use a beam of electrons
–Produce images of very high magnification and resolution*
* up to 50 million X according to some sources
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Microscopes
Electron microscopes
–Both electron beam and the specimen must be placed in a vacuum chamber, so living cells cannot be viewed.
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Microscopes
Types of electron microscopes
Transmission (TEM)
Scanning (SEM)
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Microscopes
Transmission Electron Microscope (TEM)
Reveals the fine details of a cell’s internal structure.
Chapter 3: Cell Structure Section 1: Looking at Cells
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TEM micrograph
Chapter 3: Cell Structure Section 1: Looking at Cells
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Microscopes
Scanning Electron Microscope (SEM)
Produces three-dimensional images of cell surfaces
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SEM micrograph
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Guided Practice
1. What is the difference between magnification and resolution?– Magnification means to make an image larger,
while resolution refers to the sharpness of the image.
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Guided Practice
2. Compare the magnifying power of a light microscope with the magnifying power of an electron microscope.
– Light microscopes can magnify objects up to 1000X. Electron microscopes can magnify an object up to 200 000X.
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Guided Practice
3. What is the main advantage of the transmission electron microscope?– It shows a cell’s internal structure in fine detail.
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