movement of cell

• Diffusion


  The net movement of particles from a region of their higher concentration to a region of their lower concentration, down a concentration gradient, as a result of their random movement
• Diffusion


  • How molecules move in and out of cells through the cell membrane
  • Molecules that cells need move into the cell for use in metabolic reactions and storage
  • Waste products that need to be disposed of move out of the cell into the blood to be excreted
• Diffusion occurs


  Until the number of nutrients inside and outside the cell are balanced
• Factors influencing diffusion


  • Surface area
  • Temperature
  • Concentration gradient
  • Distance
• Osmosis

  The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane
• Role of water


  • Acts as a solvent
  • Allows transport of dissolved substances
  • Needed for digestion
  • Needed for excretion
• Water potential


  A measure of the tendency of water to move from one area to another by osmosis
• Osmosis experiment using dialysis tubing

  1. Dialysis tubing filled with concentrated sucrose solution suspended in distilled water

  2. Water moves from higher water potential (distilled water) to lower water potential (sucrose solution) through the partially permeable membrane

  3. Water level outside the tubing decreases as water moves into the tubing
• Effects of osmosis on plant and animal cells

  • In dilute solution, water moves into the cell, causing it to become turgid (swollen)
  • In concentrated solution, water moves out of the cell, causing it to become flaccid (shrunken)
  • Plant cells can become plasmolysed if too much water is lost
• Turgor pressure


  The pressure on the cell wall from the cell membrane pushing upon it
• Importance of osmosis in plants

  • Plants obtain water by osmosis through their roots
  • Water transports minerals and nitrate ions
  • Water maintains cell turgidity, providing support and strength
• Active transport


  The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, against a concentration gradient, using energy from respiration
• Active transport


  • Used when diffusion or osmosis cannot be relied upon
  • Protein carriers in the cell membrane capture molecules on one side and transport them to the other side, using energy from respiration