Cell Transport

Please take out your notes!

Explain the role of cell membranes as a highly selective barrier during passive and active transport.

• Diffusion

• Osmosis

Can you die from drinking too much water?

Cell Membrane: Semi-permeable barrier that regulates the movement of substances in and out of the cell.

Semi-Permeable: Only allows certain substances to pass through.

Cell Transport: Movement of substances in and out of the cell

• Requires energy (ATP energy)

• Molecules move from LOW to HIGH concentrations

  • Concentration means "amount of"

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Active TransPort

• Does NOT require energy

• Molecules move from HIGH to LOW concentrations

  • Concentration means "amount of"

Passive Transport

• Diffusion = Movement of molecules from high to low concentrations.

  • Ex. Salt or sugar

• Osmosis = Movement of WATER across the membrane from high to low. ONLY WATER!!

Diffusion and Osmosis

• How water moves in different solutions

• Water moves towards higher solute concentrations!

• All of these are PASSIVE transport!

• No net movement of water

• Concentration of solutes inside and outside the cell are the same

• Cell stays the same

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Isotonic

• Water moves out of the cell

• Higher concentration of solutes outside the cell than inside the cell

• Cell shrinks

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Hypertonic

• Water moves into the cell

• Higher concentration of solutes inside the cell than outside the cell.

• Cell swells/expands and can rupture.

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Hypotonic