Cell Theory Timeline

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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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How do cells carry out life processes?

• Regulates what enters and exits the cell 
• Helps the cell obtain and metabolize nutrients
  (ENERGY)
• Involved in growth and reproduction
• Involved in protein synthesis and
  modifying/shipping proteins
• Stores and digests nutrients/ digests harmful
  chemicals
• Provides structure for the cell and mobility

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How can we view cells?
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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
• Observes many single celled organisms, (like
  blood cells, animal sperm cells, bacteria from
  his own teeth! He called them animalcules )

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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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Light Microscope

• Uses light to produce enlarged image
• Light rays bend when passing through lens
• Simple microscope magnifying glass
• Compound microscope 2 lenses
• Multiply the magnification of each lens to get
  the total magnification.

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Onion Cells
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(No Transcript)
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Electron Microscope

• First microscope constructed in 1931
• Higher magnification (up to 2 million times)
• Scanning electron microscopy can create 3-D
  shapes
• Expensive and large
• Image is not in color
• Sample must be dry (cannot view living organisms)

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Fluorescent Microscopy

Principle of Fluorescence1. Energy is absorbed by the atom which becomes excited.2. The electron jumps to a higher energy level.3. Soon, the electron drops back to the ground state, emitting a photon (or a packet of light) - the atom is fluorescing.
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Cell Diversity

• Shape There are many cell shapes. The function
  of the cell influences the shape of the cell.
• For example, skin cells are flat, nerve cells
  have extensions.

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Skin Cells
Nerve cell
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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