The%20Smallest%20Units%20of%20Life

1
The Smallest Units of Life

• Cells

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What are Cells?

• Cells are the smallest unit that can carry out
  life functions
• All cells have a cell membrane and cytoplasm
• The shape of a cell helps its function
• ex. Red blood cells are circular
• They are prokaryotic (no nucleus) or
• eukaryotic (nucleus)
• Cells can stand alone or work together in
  multi-cell organisms
• cells tissues organs
  organ system organism

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What kinds of cells are there?

• Plant
• have cell walls
• have a definite shape
• have no lysosomes
• have chloroplasts
• large central vacuole

• Animal
• have no cell walls
• can be any shape
• have no chloroplasts
• have lysosomes
• small vacuoles
• have a cytoskeleton

4
The Cell Theory

• With the invention of the microscope in the
  1600s people were able to explore the world that
  they could not see
• They looked at blood, tartar, pond water, plants
  and animals
• 3 men contributed to the cell theory Schleiden,
  Schwann and Virchow

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Cell Theory Continued

• Schleidens contribution was to state that all
  plants are made up of cells
• Schwanns contribution was to state that all
  animals are made up of cells
• Virchows contribution was to state that all
  cells come from other cells
• Their ideas combined to create the cell theory
• All organisms are made up of one or more cells
• The cell is the basic unit of all life
• All cells come from other cells

6
Cell Processes-How cells move things across the
membrane

• The cell membrane determines what goes in and out
  of the cell
• It is selectively permeable
• this means that materials that can get through
  easily will and those that are larger must get
  in on their own
• Materials move in and out of cells in 3 ways

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Cell Processes-How cells move things across the
membrane cont.

1. Osmosis-movement of water from an area where
   there is a lot to where there is a little
2. Diffusion-movement of molecules from where there
   is a lot to where there is a little
3. Active Transport-when energy is required to move
   material across the membrane