The Plasma Membrane -

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Aim How cell membrane organized?
HW 10 1. Complete the handout on the cell

• Do now You have 5 min.
• Explain how the following structures
• Nucleolus
• Ribosomes
• Endoplasmic reticulum
• cytoplasm

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The Plasma Membrane

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Photograph of a Cell Membrane

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I. Cell Membrane A. General

• 1. Flexible and allows a unicellular organism to
  move

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B. Function

• Maintain a high concentration of materials
• in the cell.

2. Keep harmful materials out.
3. Control the movement of materials into
and out of the cell.
4. Let the cell sense its environment.
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5. Protective barrier 6. Regulate transport in
out of cell (selectively permeable) 7. Allow
cell recognition 8. Provide anchoring sites for
filaments of cytoskeleton
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Membrane Components
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Proteins Are Critical to Membrane Function
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• 9. Provide a binding site for enzymes
• 10. Interlocking surfaces bind cells together
• 11. Contains the cytoplasm (fluid in cell)

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C. Maintains homeostasis

• Balanced internal condition of cells.
• Also called equilibrium
• Maintained by plasma membrane controlling what
  enters leaves the cell.

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• Review
• Explain what would happen to a cell if the cell
• membrane did not do its job properly.

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D. Structure of the Cell Membrane

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1. Membrane Components
Proteins (peripheral integral)
Phospholipids
Cholesterol
Carbohydrates (glucose)
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a. Phospholipids

• 1. Make up the cell membrane

a. Contains 2 fatty acid chains that are nonpolar
b. Head is polar contains a PO4 group

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FLUID MOSAIC MODEL

• 1. FLUID- because individual phospholipids and
  proteins can move around freely within the layer,
  like its a liquid.
• 2. MOSAIC- because of the pattern produced by the
  scattered protein molecules when the membrane is
  viewed from above.

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Cell Membrane
Polar heads are hydrophilic water loving
Nonpolar tails are hydrophobic water fearing
Makes membrane Selective in what crosses
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Cell Membrane
Hydrophobic molecules pass easily hydrophillic
DO NOT
The cell membrane is made of 2 layers of
phospholipids called the lipid bilayer
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Solubility

• Materials that are soluble in lipids can pass
  through the cell membrane easily

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Semipermeable Membrane
Small molecules and larger hydrophobic molecules
move through easily. e.g. O2, CO2, H2O

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Semipermeable Membrane
Ions, hydrophilic molecules larger than water,
and large molecules such as proteins do not move
through the membrane on their own.