Download 1.1 Cell Theory and the Microscope - Hutchison

1.1 Cell Theory
Pages 7-10
Characteristics of Living Things
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Try to maintain a constant internal environment
Reproduce
Made up of cells
Moves
They make their own food or feed on another living thing
Consumes gas and releases gas
Senses/responds to changes in their environment
Cell Theory
• All living things are composed of one or more
cells
• Cells are the basic structural and functional
units of life
• All cells arise from the division of other cells
Observing Cells
• The simple light microscope
Observing Cells
• Compound Light Microscope
Brightfield
• The image is viewed against a bright
background
Darkfield
Bright image against a dark background.
Compound Light Microscope
Magnification
• Multiply ocular lens magnification by objective
lens magnification
• 10X x 40X = 400X magnification
Resolution
Good resolution produces a clean, sharp image
Phase Contrast Microscope
• Takes advantage of the slight differences in a
specimen’s capacity to bend light rays,
enhancing light and dark regions
• You can observe living specimens
• Magnification up to 1500X. Resolution
• Images must be photographed or displayed on
a monitor.
Phase Contrast Specimen
• Comparing brightfield with Phase Contrast
Paramecium
Observing Cells
The Transmission Electron Microscope (TEM)
Aims a beam of electrons through a thin slice of
specimen.
Cell must be dead, coated in plastic and shaved
1 000 000X magnification. 0.2nm resolution
Greater resolution and magnification.
Image must be photographed or showed on a
monitor
Images using TEM
• Embryo of C. elegans (1mm long nematode)
• A mitochondria in a mammalian lung cell
Observing Cells
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The Scanning Electron Microscope (SEM)
Reflects electrons from the surface of the specimen
Thicker samples can be used
Use magnets to focus the beam of electrons
3-D image, 300 000X magnification, resolution 10nm
Greater contrast and depth
SEM must be photographed or viewed on a monitor
SEM images
• Spider
• pollen