Cells - Cells The size of cells and their contents 20 nm 20...

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Unformatted text preview: Cells The size of cells and their contents 20 nm 20 m 20 mm 2 mm 0.2 mm 2 m 2 nm 0.2 nm 0.2 m Robert Hooke (1665) Examined a thin slice of cork tissue Observed honeycombed compartments he called cellulae (L, small rooms) The term became cells Matthias Schleiden and Theodor Schwann Proposed the first two statements of the cell theory in 1838-39 The Cell Theory In its modern form, the cell theory includes three principles The Cell Theory 1. All organisms are composed of one or more cells 2. Cells are the smallest living things 3. Cells arise only by division of a previously existing cell Cells range in size from a few micrometers to several centimeters Most cells are small because larger cells do not function efficiently It is advantageous to have a large surface- to-volume ratio As cell size increases, volume grows much faster than surface area Cell Size Surface-to-volume ratio Visualizing Cells Few cells can be see with the unaided eye A scale of visibility Visualizing Cells We cant see most cells because of the limited resolution of the human eye Resolution is the minimum distance two points can be apart and still be seen as two points Resolution of the human eye is 100 One way to increase resolution is to increase magnification, using microscopes There are two main types of microscopes Light Microscopes Use light as the illuminating source 2 8 .3 6 m 6 7 .7 4 m Light Microscopes Use light as the illuminating source 3 2 .8 1 m 2 6 .6 m Electron Microscopes Use a beam of electrons to produce the image 2 .5 6 m 6 .7 6 m The Plasma Membrane Encases all living cells Its basic structure is represented by the fluid-mosaic model Phospholipid bilayer with embedded proteins Phospholipid structure The Plasma Membrane...
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This note was uploaded on 04/02/2008 for the course BIO 110 taught by Professor N/a during the Fall '08 term at Cal Poly Pomona.

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Cells - Cells The size of cells and their contents 20 nm 20...

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