chapter 7
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Chapter 7. A Tour of the Cell. The Size Range of Cells. Prokaryote No membrane bound nucleus or organelles DNA is concentrated in a region called the nucleoid 1 – 10 μ m in diameter Include bacteria and archaea. Eukaryote Membrane-bound organelles - PowerPoint PPT PresentationTRANSCRIPT
The Size Range of Cells
A Tour of the CellProkaryote
• 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
A Tour of the Cell
Animal Cell
Plant Cell
Animal CellHave:
MitochondriaNucleusCell MembraneRough & Smooth ERRibosomesGolgi ApparatusCytoplasmCytoskeletonPeroxisomes
Also:LysosomesCentriolesFlagella and Cilia
Plant CellHave:
MitochondriaNucleusCell MembraneRough & Smooth ERRibosomesGolgi ApparatusCytoplasmCytoskeletonPeroxisomes
Also:ChloroplastsVacuolesCell WallPlasmodesmata
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 Field of vision diameter
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?
Field of Vision
Field of Vision
• 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 MicroscopesElectron 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
TEM
• Transmission Electron Microscope
TEM• Beam of electrons pass through specimen
• Magnifies up to 500,000x
• 2-D image• Non-living
specimens only
TEM
Collagen Fibrils in the cornea
TEM• Plant Cell-22,500X
• C = ChloroplastER = Endoplasmic ReticulumG = Granum M = Mitochondrion S = Starch GrainT = Thylakoids V = Vacuole W = Wall
SEM
• Scanning Electron Microscope
• Electrons bounce off surface
• Specimen placed in vacuum chamber
SEM•
• Non-living specimens
• 3-D image• Magnifies up to
60,000x
SEM
• Technician monitors image on screen
SEM
Pollen Grain
Scanning Tunneling Microscope
• Developed in 1980’s
• Can view atoms on surface of objects
• Non-living• 3-D image• Magnifies up to
100 million x
STM
• Barium, Copper, and Oxygen atoms
STM• Silica atoms
• A nanometer (nm) is one millionth of a millimeter