transport in cells

• Diffusion


  The spreading out of particles from an area of higher concentration to an area of lower concentration
• Diffusion


  • Only very small molecules (e.g. oxygen, glucose) can diffuse through cell membranes
• Osmosis


  The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• Net movement of water molecules is from higher to lower water concentration
• Factors that increase rate of diffusion

  • High concentration gradient
  • High temperature
  • Large surface area
• Active transport


  The movement of a substance against the concentration gradient, requiring energy from respiration
• Active transport allows


  • Mineral ions (for plant growth) to be absorbed from the soil into root hair cells
  • Glucose (for cell respiration) to be absorbed into the bloodstream from the gut