CH 6 A Tour of the Cell

CH 6 A Tour of the Cell - CHAPTER 6 A TOUR OF THE CELL 10 m...

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CHAPTER 6 A TOUR OF THE CELL 10 µm
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A TOUR OF THE CELL The cell Microscope Cell Size Limits Prokaryotes vs Eukaryotes Endomembrane System The Cell and its Organelles The Cytoskeleton Intercellular Junction Outline:
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The Cell The organism’s basic unit of structure and function Single-celled organisms and Multicellular organisms To study cells, biologist use microscopes and the tools of biochemistry
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MICROSCOPY Microscope usefulness based on resolution. Ability to distinguish 2 points as separate Light Microscope (Fig. 6.3) Limited by “long” wavelength 1,000 times the size Electron Microscope (Fig. 6.4) Shorter wavelengths than visible light, finer resolution (special staining) Transmission electron microscopes ( TEM ) to study the internal ultrastructure of cells. Scanning electron microscopes ( SEM ) to study surface structures. Unaided eye
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Surface are to volume at the cellular level Surface area to volume ratios were (or for some of you will be) a major focus of Bio 115. In general, you should know that as cells or organs or anything else get bigger in size, the SA:Vol ratio gets smaller With size increase, volume increases faster than surface area. What implications does this have for exchange and storage?
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Cell Size Limits Metabolic requirements also set an upper limit to the size of a single cell. As a cell increases in size its volume increases faster than its surface area. Smaller objects have a greater ratio of surface area to volume facilitates exchange of materials in and out of cell Surface area increases while total volume remains constant 5 1 1 Total surface area (height × width × number of sides × number of boxes) Total volume (height × width × length × number of boxes) Surface-to-volume ratio (surface area ÷ volume) 6 1 6 150 125 12 750 125 6 Figure 6.7
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Lacks a true nucleus (nucleoid) No membrane-enclosed organelles 0.1 – 10 μ m in diameter ( Escherichia coli is typical at 0.3 μ m or 300nm) Has a true nucleus Contains membrane-enclosed organelles surrounded by a cell membrane 7 – 100 μ m in diameter (10 μ m is a typical cell diameter) Prokaryotic and Eukaryotic Cells Differ in Size and Complexity
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Prokaryotic cells
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Prokaryotes: bacteria (Monera) Eubacteria (“true bacteria) Gram negative Gram positive (there are exceptions: some bacteria lack cell walls entirely, e.g. Mycoplasma ) Archaea (Archaebacteria )-often associated with extreme environments
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Prokaryotes Overview: They’re (Almost) Everywhere! Most prokaryotes are microscopic
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CH 6 A Tour of the Cell - CHAPTER 6 A TOUR OF THE CELL 10 m...

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