lect21_euks

lect21_euks - Bacterial vs Eukaryotic Cells 5 m Have you...

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1 Bacterial vs Eukaryotic Cells Biology 2A: Chapter 21 5 μm Figure 6.32 ± An estimated 5 x 10 30 bacteria (and archaea) are alive today ± Bacteria contain 50% of the carbon and 90% of the nitrogen and phosphorous found in organisms ± Bacteria run some of the earth’s major ecosystem functions (e.g., the carbon and nitrogen cycles) ± Bacteria are the dominant life-form on our planet (numerically, by volume, by mass, and by ecosystem-function!) Have you underestimated bacteria? Bacterial colonies Bacteria and You ± “In every person’s body, there are 10 times as many microbial cells as there are human cells.” Science News 2007 ± “In any one human, there are a hundred times as many microbial genes as there are human genes” David Relman, Stanford, Science News 2007 ± An estimated 10 12 bacteria live on your skin. An additional 10 14 bacteria and archaea live in your gut. (You consist of 10 13 cells) “Where’s the Lysol!?!” ± Are there benefits to having bacteria on and in you? – Immune system function, vs. allergies • Hygiene hypothesis – Gut function, vitamins, nutrition – Protective role (against colonization) – Distinctive body scent (also related to certain immune system proteins) Why are cells so small? ± Propose a hypothesis to your neighbor.
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Cell size is restricted by: ± The total amount of a materials transported across the membrane per second ± The total energy requirements per unit mass ± The speed with which materials are distributed throughout the cell volume Complete the table above. How do you calculate surface area? ± Size of a face in cube 1: 4mm x 4mm ± # of faces: 6 SA = 4mm x 4mm x 6 = 96 mm 2 ± Size of a face in cube 3: 1mm x 1mm ± # of faces: 6 ± SA = 1mm x 1mm x 6 x 64 cubes = 384 mm 2 How do you calculate volume? ± Volume of cube 1: 4mm x 4mm x 4mm Volume = (4mm) 3 = 64 mm 3 ± Volume of cube 3: (1mm) 3 x 64 ‘cells’ = 64 mm 3 How do you calculate SA / volume ratio? ± SA of cube 1 / Volume of cube 1: 96 mm 2 / 64 mm 3 = 1.5 =1.5 to 1 ± SA of cube 1 / Volume of cube 3: 384mm 2 / 64 mm 3 = 6 = 6 to 1 Each part of the cell needs nutrients to stay alive. What problem does this create for the 3 sizes of
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lect21_euks - Bacterial vs Eukaryotic Cells 5 m Have you...

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