CELL TRANSPORT

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CELL TRANSPORT

• p. 97

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• Molecules are in constant motion
• Molecules move randomly

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PASSIVE TRANSPORT

• Movement of substances across plasma membrane NOT
  requiring energy input

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FORMS OF PASSIVE TRANSPORT

• DIFFUSION
• OSMOSIS
• FACILITATED DIFFUSION
• ION CHANNELS

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DIFFUSION

• Simplest form of passive transport
• Molecules move from HIGH concentration to areas
  of LOW concentration
• HIGH LOW

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CONCENTRATION GRADIENT

• Difference in the concentration of molecules
  across a distance

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EQUILIBRIUM

• Occurs when concentration is the same throughout
• Movement of molecules still occurring
• Movement in and out is at equal rates
• IN OUT
• IN OUT

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OSMOSIS

• Movement of WATER molecules from HIGH
  concentration to LOW concentration
• Diffusion of water
• All osmosis is diffusion BUT not all diffusion is
  osmosis.

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TURGOR PRESSURE

• Pressure exerted by water molecules against cell
  wall
• Osmotic pressure (water pressure)
• Turgidity state of being swollen

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THREE TYPES OF SOLUTIONSp. 99

• HYPOTONIC
• HYPERTONIC
• ISOTONIC
• Prefixes refer to solute concentration of
  solution in relationship to concentration inside
  the cell

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HYPOTONIC SOLUTION outside the cell

• Example distilled water
• Solute concentration low
• Water (solvent) concentration high
• Water moves into the cell
• Turgor pressure INCREASES
• Final state if allowed to continue
• CYTOLYSIS
• p. 100

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CYTOLYSIS

• Cyto--- cell
• --lysis splitting of cell
• Bursting of cell due to too much turgor pressure

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CONTRACTILE VACUOLE

• Eliminates excess water from protiststo maintain
  homeostasis
• Paramecium / ameoba
• radial canal
• Collects excess H2O

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HYPERTONIC SOLUTION outside the cell

• Example SALT (ocean) water
• Solute concentration high
• Water (solvent) concentration low
• Water moves out of the cell
• Turgor pressure DECREASES
• Final state if allowed to continue
• PLASMOLYSIS

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PLASMOLYSIS

• Shrinking of cell due to lack of turgor pressure
• Vacuole no longer pushing against cell wall
• Plant wilts

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ISOTONIC SOLUTION
outside the cell

• Example TAP water
• Solute concentration equal to cell
• Water (solvent) concentration equal to cell
  Water moves into and out of the cell AT THE SAME
  RATE
• Turgor pressure STAYS THE SAME
• Final state if allowed to continue
• EQUILBRIUM

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FACILITATED DIFFUSION

• CARRIER PROTEINS
• Integral and peripheral proteins
• Help large molecule to enter cell

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ION CHANNELS

• FORM OF PASSIVE TRANSPORT
• Na Ca K Cl-
• Respond to
• Stretching of cell membrane
• Electrical signals
• Chemical signals

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ACTIVE TRANSPORT

• Movement of substances across plasma membrane
  requiring energy input
• Molecules move from LOW concentration to areas of
  HIGH concentration

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Forms of Active Transport

• Sodium-potassium pump
• Endocytosis
• pinocytosis
• phagocytosis
• Exocytosis

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SODIUM-POTASSIUM PUMP

• Uses specific type of protein
• Energy supplied by ATP
• Ions are required for nerve signaling

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ENDOCYTOSIS

• Engulfing (intake) of large molecule by plasma
  membrane
• Pinocytosis
• Engulfing (intake) of large liquid molecule
• Phagocytosis
• Engulfing (intake) of large food molecule

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EXOCYTOSIS

• RELEASING of large molecule outside of the cell
• Waste removal