Moving Materials Across The Cell Membrane

1
Moving Materials Across The Cell Membrane

• Two ways
• 1. Passive Transport (PT)
• Requires no cellular energy
• 2. Active Transport (AT)
• Requires cellular energy (ATP)

2
Three Types of PT

• Diffusion
• Osmosis
• 3. Facilitated Diffusion

3
Diffusion

• Molecules move from an area of high concentration
  to an area of low until Equilibrium is
  reached where levels are equal.

4
Diffusion

• Small molecules like O2 and CO2 can diffuse
  across the plasma membrane. Large molecules (ex.
  Glucose) or ions (an ion is a charged particle)
  cant pass through by diffusion.

5
Osmosis

• Special type of diffusion involving water passing
  through a selectively permeable membrane.
• Water always move from an area of high to an
  area of low .

6
How Osmosis Works
Dilute sugar solution (Water more concentrated)
Concentrated sugar solution (Water less
concentrated)
Sugar molecules
Movement of water
Selectively permeable membrane
7
Osmosis Cellular Environments

• Hypotonic water outside cell is greater
  than water inside cell.
• Hypertonic water outside is less than water
  inside.
• Isotonic water outside equals water
  inside.

8
Animal Cell

• Hypotonic Solution
• high H2O
• outside , H2O flows into cell , pressure
  builds up , cell bursts which is called cytolysis.

9
Animal Cell

• Hypertonic Solution
• low H2O outside , H2O flows out of cell
  pressure drops , cell becomes dehydrated and
  shrivels up.

10
Animal Cell

• Isotonic Solution
• The H2O outside the cell equals the H2O
  inside the cell. NO change in cell. H2O moves in
  and out at the same rate.

11
Plant Cell

• Hypotonic Solution
• high H2O outside the cell , H2O flows in ,
  pressure builds up , cytoplasm pushes against
  cell membrane wall. This pressure is Turgor
  Pressure. The cell looks stiff or Turgid.

12
Plant Cell

• Hypertonic Solution
• low H2O outside cell , H2O flows out ,
  pressure drops, plasma membrane may collapse
  which is called plasmolysis. The cell is referred
  to as being wilted or flaccid.

13
Plant Cell

• Isotonic Solution
• The H2O outside the cell equals the H2O
  inside the cell. NO change in the cell. H2O moves
  inside outside at the same rate.

14
Facilitated Diffusion

• Form of PT (no ATP)
• Uses Carrier Channel Proteins in cell membrane to
  transport large molecules or ions across cell
  membrane.
• These channel proteins act as ports , shielding
  these molecules from the cell membrane.
• Still moving from an area of high to an area
  of low .

15
Glucose molecules
Protein channel