7'3 Passive Transport

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7.3Passive Transport
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Passive Transport

• Homeostasis is very important to a cells vitality
• Cells are going to need to move substances into /
  out of the cell
• Process called passive transport
• REQUIRES NO ENERGY

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Types of Passive Transport

• Diffusion
• Osmosis
• Facilitated Diffusion
• Diffusion through Ion Channels

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Diffusion

• Def The movement of molecules from an area of
  higher conc. (concentration) to an area of lower
  conc.
• Simplest type of passive transport
• The differences in the concentration is called
  the concentration gradient

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Diffusion-

• If there are no outside influences the solute
  will reach equilibrium
• Def when the concentration of molecules of a
  substance is the same throughout.

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Diffusion and the Cell Membrane

• The ability of a molecule to diffuse across a
  membrane depends on the size and type of the
  molecule and the chemical nature of the membrane
• ie hydrophobic and hydrophilic substances

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Osmosis-

• Def the process by which water molecules diffuse
  across a cell membrane from an area of high
  concentration to an area of lower concentration

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Direction of Osmosis

• When the concentration of the solute is Higher on
  the outside of the cell than in the cytoplasm the
  cells is said to be Hypertonic
• Water will rush out of the cell

• When concentration of solute is Lower on the
  outside of the cell than in the cytoplasm the
  cell is Hypotonic
• Water will rush into the cell

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Hypotonic, Hypertonic, Isotonic

• Hypotonic- water rushes into the cell
• Cell swells. If it swells too much it could
  explode
• Hypertonic water rushes out of the cell
• Cell shrinks and appears to have spikes
• Isotonic- the concentrations on both sides of the
  cell are equal thus there is no net movement
• Cell remain original shape

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Isotonic
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Hypotonic
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Hypertonic
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Turgor Pressure

• The pressure that water exerts on the cell walls
• In hypertonic solution there is little waterso
  there is little pressure exerted on the cell
  wallsplant wilts

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Turgor Pressure
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Facilitated Diffusion

• The process of substances moving down the
  concentration gradient with the assistance of a
  carrier protein
• Requires NO ENERGY and each carrier molecule is
  SPECIFIC for a certain molecule

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Ion Channels

• A membrane protein that provides a passageway
  across the cell membrane for ions to pass
  through. Each channel is for a certain ion only.

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Active Transport
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Active Transport

• Requires energy.
• Two types
• Cell Membrane Pumps
• Endo/Exocytosis

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Cell Membrane Pumps

• Moves substances up the conc. Gradient
• From an area of low to high
• Sodium-Potassium Pump
• Pumps Sodium out of the cell and (Na)
• Pumps Potassium into the cell (K)
• 3 Na ions pumped out with the use of ATP and on
  the return 2 K come into the cell
• As result electrical gradient is produced
• Example Muscles

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Exocytosis Endocytosis

• Some molecules are too large to enter
• Requires Energy
• Endo-into
• Exo- out of

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Endocytosis

• Cells ingest macromolecules
• The cell folds on itself and engulfs the
  substances the macromolecules are surrounded by
  membranes
• Pinocytosis- contains solutes or fluids
• Phagocytosis- contains large particles or cells

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Exocytosis

• Vesicles in the cytoplasm fuse with the cell
  membrane, releasing their contents into the
  cells external environment
• Usually wastes or proteins that were made on the
  cells ribosomes

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