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WHEN/WHY DO CELLS DIVIDE?

WHEN/WHY DO CELLS DIVIDE?. BIGGER IS NOT BETTER!. IMPORTANCE OF CELL MEMBRANE Controls what goes into/out of a cell All cells possess a cell membrane Cells must have a membrane surface large enough for all necessary exchanges. O 2 , CO 2 , H 2 O. SURFACE AREA TO VOLUME RATIO.

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WHEN/WHY DO CELLS DIVIDE?

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  1. WHEN/WHY DO CELLS DIVIDE?

  2. BIGGER IS NOT BETTER! • IMPORTANCE OF CELL MEMBRANE • Controls what goes into/out of a cell • All cells possess a cell membrane • Cells must have a membrane surface large enough for all necessary exchanges. • O2, CO2, H2O

  3. SURFACE AREA TO VOLUME RATIO • Smaller cells have LARGER SA/V ratios! • Larger cells have SMALLER SA/V ratios!

  4. SURFACE AREA TO VOLUME RATIO • As cells increase in size, the volume increases more rapidly than does surface area. • This makes it more difficult for nutrients to diffuse into the center of a cell. • The nucleus of a cell is often a central structure!

  5. CARDS READY!! Here we go…

  6. Which cell would be more efficient at delivering Oxygen to the nucleus? • A 3 cm cell • A 2.5 cm cell • A 5 cm cell • Oxygen doesn’t diffuse into cells.

  7. Which type of cells need a plasma membrane? • Eukaryotic • Prokaryotic • Plant • All of the above

  8. Which of the following would have the lowest efficiency in ridding the cell of waste? • A cell with a 15 SA/V ratio • A cell with a 3 SA/V ratio • A cell with a 6 SA/V ratio • Not enough information to answer.

  9. Which of the following explains why cell need to remain small in order to be efficient? • Materials diffuse faster in a smaller cell • The nucleus does not have very far to travel in a smaller cell. • Materials have a shorter distance to travel to reach the nucleus. • None…the cell should remain bigger.

  10. Moving on….

  11. CELLS DIVIDE FOR: • GROWTH • As the number of cells increases, an organism grows. • Differentiation • REPAIR • Repair damaged tissue • Mending skin, bone, blood • Replacing old cells

  12. CELLS DIVIDE FOR: • REPRODUCTION • ASEXUAL • One organism produces an identical copy of itself • SEXUAL • Two organisms join genetic material to produce a unique individual

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