Cell Transport

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Cell Transport
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Cell Transport

• Substances move in and out of cells by passive
  and active transport

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Passive Transport

• No energy required
• Diffusion, Osmosis, Net movement

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Diffusion

• The random movement of molecules from an area of
  high concentration to an area of low
  concentration.
• With the concentration gradient.
• Animation
• Animation2

Conc. Grad
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• Rate depends on
• 
  fast slow
• Size of molecules
• Temperature
• State of matter
• Concentration of chemicals

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Osmosis

• Net movement of water molecules from an area of
  high water concentration to an area of low water
  concentration, through a semi-permeable membrane.
• Animation Animation2
• Hypertonic more solute and less water
• Hypotonic less solute and more water
• Isotonic same conc. of solute and water

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Think (dont write)

• Most marine fish die if transferred to
  freshwater.
• When a drop of blood is mixed with distilled
  water, the blood cells burst.
• Living plant tissues that had lost water become
  firm when supplied with water.

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Net movement

• The overall movement
• e.g. When oxygen diffuses into a cell, some
  oxygen molecules are moving out of the cell, but
  more are moving inwards.

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Osmoregulation

• The control of water in a cell.
• Plasmolysis
• Water leaves cell and membrane shrinks from wall.
  
• Cell becomes flaccid.
• Full plasmolysis is irreversible.
• Animation

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• Turgor
• Water enters cell causing it to swell
• Cell becomes turgid
• Cell wall prevents rupture
• Animation

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Active Transport

• Energy (ATP) required
• Endocytosis (phago- and pino-), Exocytosis, Ion
  pumps
• E.g. reabsorption of glucose by kidney, salt
  uptake by the roots of plants, amino acid uptake
  by fungi

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• The movement of substances from an area of low
  concentration to an area of high concentration.
• Against the concentration gradient

Conc. Grad
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Endocytosis

• Movement in (enter)
• Phagocytosis cell eating forms a food
  vacuole. Lysomes fuse to enable digestion.
• Pinocytosis cell drinking forms a vesicle
• E.g.Amoeba and WBC pseudopodia
• Animation

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Exocytosis

• Movement out (exit)
• Vesicles bud off from golgi apparatus or ER,
  vacuole fuses with cell membrane and expels
  contents
• Secretions e.g. digestive enzymes released,
  glands
• Animation

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Ion Pumps

• Proteins in the cell membrane can actively
  accumulate specific ions on one side of the
  membrane to control the amount
• Animation
• Animation2

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Role of the cell membrane

• How the structure controls it