Plasma Membrane

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Plasma Membrane

• Structure and Function

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Plasma Membrane

• Made of a Lipid Bi-layer (two parts)
• Phospholipid heads are hydrophilic (water loving)
• Phospholipid tails are hydrophobic (water
  fearing)
• Described as a Fluid-mosaic.
• Proteins, glycolipids, carbohydrates, and
  cholesterol are embedded in the bi-layer.

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Fluid Mosiac Model?

• This refers to the property of the bi-layer which
  can move sideways in relation to each other.
• Cells are flexible/pliable due to this property.
• Also, the bi-layer is studded with several
  different types of proteins.
• Each protein has a different function.

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Proteins found in bi-layer

• Channel Proteins substance can move freely
  through.
• Carrier Proteins using a substrate to help move
  substances across the membrane.
• Receptor protein has a shape that allows a
  specific molecule to bind to it, causing protein
  to react.
• Enzymatic protein carry out metabolic reactions.

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Passive Transport

• Diffusion movement of molecules from an area of
  high concentration to an area of low
  concentration.
• Osmosis the movement of WATER molecules from an
  area of high concentration to an area of low
  concentration.
• Facilitated transport movement of molecules
  (like diffusion) using a transport proteins.
• NONE OF THESE MECHANISMS USE ENERGY.

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Facilitated Diffusion of glucose from liver cells.
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Active Transport
These mechanisms require energy to move molecules.

• Ion pumps
• Molecules can be positively or negatively
  charged.
• Must use ATP to move ions against a concentration
  electrical gradient.
• Cotransport
• Uses the element Hydrogen to assist in the uptake
  of molecules.
• Endocytosis/Exocytosis
• The cell literally taking something
  inside/outside by engulfing or receptor
  mediation/expulsion.

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Ion Pump
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Active Transport (cont.)

• Exocytosis the expulsion of materials from a
  cell by the fusion of a vesicle with the plasma
  membrane.
• http//www.linkpublishing.com/Videos/transport/par
  a_exo.wmv

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Tonicity?

• Cells are continually adjusting the composition
  of liquids inside and outside of the cells.
• The different mixtures are categorized due to
  their effects on a cell.
• Hypertonic solutions
• Hypotonic solutions
• Isotonic solutions
• http//www.linkpublishing.com/Videos/transport/elo
  dea_hyper.wmv

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Hypotonic Solution

• http//www.linkpublishing.com/Videos/transport/elo
  dea_hypo.wmv
• A is a cell in a hypertonic solution while B
  is a cell in a hypotonic solution.

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Isotonic Solution

• http//www.linkpublishing.com/Videos/transport/blo
  od_isotonic.wmv

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What does Tonicity do?

• Cells can regulate the amount of specific
  dissolved substances within them, thereby
  regulating the amount of water entering or
  leaving the cell through osmosis.
• Plant cells use the principle of tonicity to draw
  water from the soil to the leaves. The series of
  cells along the chosen path of water adjust their
  tonicity to move water throughout the entire
  plant.

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Tonicity cont.

• Medical use in I.V. fluids.
• I.V. fluids are usually hypotonic. Why?
• What advantage would there be for an isotonic
  I.V. solution?
• What is the make up of a sports drink?