The Plasma Membrane

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The Plasma Membrane
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Plasma Membrane

• Made of double layer of phospholipids
• Proteins, lipids, and carbohydrates scattered
  throughout
• Surrounds outside of ALL cells
• Controls what enters or leaves the cell
• Helps maintain homeostasis
• Selectively permeable allows some things into
  cell, while keeping other things out

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The Plasma Membrane
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The Plasma Membrane Structure

• Phospholipid Bilayer
• Barrier that only small, non polar substances can
  pass thru
• Proteins
• Helps transport molecules in and out of the cell
• Helps with flexibility
• Carbohydrates
• Extracellular (outside of cell)
• Used for identifying molecules and other cells

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Phospholipids

• Phosphate heads are hydrophilic (attract water)
• Fatty acid tails are hydrophobic (repel water)
• Make up a bilayer where tails point inward toward
  each other
• Can move laterally to allow passage of small
  molecules (O2, CO2, H2O)

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Cell Membrane Proteins

• Proteins help move large molecules or aid in cell
  recognition
• Peripheral proteins (red) are attached on the
  surface (inner or outer)
• Integral proteins (black) are embedded in the
  membrane

Integral proteins
Peripheral proteins
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Cell Membrane Carbohydrates

• Extracellular (outside of the cell)
• Used to recognize molecules and other cells

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Fluid Mosaic Model

• Fluid Properties
• Flexible membrane
• Molecules move around within the membrane
• Mosaic Properties
• Mosaic smaller parts make up whole
• Membrane is made of many kinds of smaller
  molecules