KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

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• KEY CONCEPT The cell membrane is a barrier that
  separates a cell from the external environment.

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Phosopholipids- Have three parts.Charged part
phosphate and glycerol. This part is attracted to
charged molecules of water and cytoplasm.
The fatty acid chains. These are non-polar
molecules. Attracted to other non-polar
molecules. Together they form a sort of
sandwich With the chains together and the
phosphates on the outside. This is why they are
called a bilayer (or two layer)
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• Cell membranes are composed of two phospholipid
  layers.

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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane has two major functions.

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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane has two major functions.
• forms a boundary between inside and outside of
  the cell

outside cell
inside cell
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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane has two major functions.
• forms a boundary between inside and outside of
  the cell
• controls passage of materials
• Cell membranes are composed of two phospholipid
  layers.

outside cell
inside cell
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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane is made of a phospholipid
  bilayer.

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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane is made of a phospholipid
  bilayer.
• There are other molecules embedded in the
  membrane.

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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane is made of a phospholipid
  bilayer.
• There are other molecules embedded in the
  membrane.
• The fluid mosaic model describes the membrane.

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Fluid Mosaic Model-its flexible not rigid-the
proteins do not flip -variety of molecules
embedded make it appear like a mosaic.
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Fluid Mosaic Model continued

• Types of molecules that may be embedded in the
  membrane are
• Cholesterol to give it strength.
• Proteins to help certain materials pass though
  the membrane. Some proteins are part of the
  cytoskeleton and some are specific to the type of
  cell.
• Carbohydrates act as a tag to identification tags
  to differentiate one type of cell from another.

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• Cell membranes are composed of two phospholipid
  layers.

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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane is selectively permeable.

It also means that it can actively respond and
interact with the surrounding environment.
This means that it can be passed through by
CERTAIN things at CERTAIN times.
Some molecules can cross the membrane while
others cannot.
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• Cell membranes are composed of two phospholipid
  layers.
• The cell membrane is selectively permeable.

Some molecules can cross the membrane while
others cannot.
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• Chemical signals are transmitted across the cell
  membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.

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• Chemical signals are transmitted across the cell
  membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.
• intracellular receptor

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• Chemical signals are transmitted across the cell
  membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.
• intracellular receptor
• membrane receptor