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Chapter 3

Chapter 3. Cell size and structures. http://www.cellsalive.com/cells/bactcell.htm. Internal structures Nucleoid, DNA and ribosomes, endospores Surface structures Glycocalyx –substance that surrounds the cell Cell wall, plasma membrane, outer membrane and capsule/slime layer Appendages

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Chapter 3

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  1. Chapter 3 Cell size and structures

  2. http://www.cellsalive.com/cells/bactcell.htm • Internal structures • Nucleoid, DNA and ribosomes, endospores • Surface structures • Glycocalyx –substance that surrounds the cell • Cell wall, plasma membrane, outer membrane and capsule/slime layer • Appendages • Flagella, Pili

  3. Functions (will look at in more detail later) • Nucleoid • DNA • Ribosomes • Endospores • Cell wall • Periplasmic space • Outer membrane • Plasma membrane • Capsule • Flagella • Pili • Fimbriae • Glycocalyx • Capsule • Slime layer

  4. Cells come in all sizes and shapes • Smallest cells = mycoplasmas • 0.1 – 1 uM • Largest cells = bird eggs • Longest cells = nerve or muscle cells • The general size for prokaryotes is 1-3 μm; viruses are smaller – in the nm range

  5. Cell Morphology • Morphology = cell shape • Major cell morphologies • Coccus (pl. cocci): spherical or ovoid • Rod: cylindrical shape • Spirilla: spiral shape

  6. Cell Morphologies of Prokaryotes

  7. Cell Morphologies of Prokaryotes

  8. Size: Surface-to-Volume Ratios • There are advantages to being small • Small cells contain more surface area relative to cell volume than large cells (i.e., higher S/V) • support greater nutrient exchange per unit cell volume • tend to grow faster than larger cells

  9. Surface Area • Smaller cells have more surface area for their volume

  10. SA to Volume Ratio

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