UNIT 4: Cells

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UNIT 4 Cells

• BIG IDEA There are different levels of
  organization in organisms, with cells being the
  basis of all life.

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Cell Theory Timeline
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What is a cell?

• The basic unit of structure and function of life.

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1665 Robert Hooke

• Builds compound microscopes and first to observe
  cork cells.

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Late1600s Anton van Leeuwenhoek

• Builds simple, powerful microscopes and 1st to
  see living cells
• Observes blood cells, animal sperm cells,
  bacteria from his own teeth! He called them
  animalcules

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Cell Theory

• The observations about cells from the past 150
  years is becoming more organized in the 1800s
• Schleiden, Schwann and Virchow are the scientists
  who contribute to developing a unifying cell
  theory

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• 1838 Matthias Schleiden Concludes all plants
  are made of cells
• 1839 Theodor Schwann Concludes all animals are
  made of cells.

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• 1855 Virchow
• Concludes that all cells come from pre-existing
  cells

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Cell Theory

1. All organisms are composed of one or more cells.
2. Cells are the basic units of structure and
   function in an organism.
3. Cells come only from the reproduction of existing
   cells.

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Cell Diversity

• Shape There are many cell shapes. The function
  of the cell influences the shape of the cell.
• Size Different types of cells have different
  sizes.
• 0.1 µm 100 µm
• The size of a cell is limited by the surface
  area-to volume ratio.

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Surface area-to-volume Ratio
larger

• As the cell gets ______, the surface-area-to-volum
  e ratio gets _________.
• If the cell grows beyond a certain limit, not
  enough material will be able to cross the
  membrane fast enough to provide for the increased
  volume.

smaller
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Surface area-to-volume ratio
Length of side Surface Area Volume Surface Area/ Volume
1
2
4
6
1
6
8
3
24
96
64
3/2 1.5
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Surface area-to-volume ratio

• Materials must enter through the surface.
• The bigger the cell, the smaller the surface
  area-to-volume ratio.
• If a cell is too large, there is not enough
  surface area to allow materials to pass through
  quickly enough.

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Types of Cells

• Prokaryotic vs. Eukaryotic

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Prokaryotic Cells
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• Very simple cell
• Generally smaller
• NO membrane-bound organelles (compartments)
• No true nucleus.
• DNA is found in the nucleoid region and is NOT
  separated by a membrane.
• Example is bacteria.

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Eukaryotic Cell
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• More complex cells
• Generally bigger
• Contains membrane-bound organelles
• Has a true nucleus
• Region of where DNA is stored and is separated by
  a membrane.
• Examples are animals plants

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Pop Quiz!

1. Who is credited for first seeing cells?
2. According to the Cell Theory, where do all cells
   come from?
3. Which cells are simpler Prokaryotic or
   Eukaryotic?
4. Which cells contain membrane-bound organelles?
5. Which type of cells do you have?