Cell Transport Mechanisms

Cell Transport

• Diffusion

  • Passive transport mechanism
  • Small nonpolar molecules (e.g., oxygen, carbon dioxide) pass directly through the cell membrane
  • Movement occurs from high to low concentration
  • No energy or proteins required

• Osmosis

  • Passive transport specifically for water
  • Water moves across the cell membrane from high to low concentration
  • Requires no energy or proteins

• Facilitated Diffusion

  • Passive transport helped by carrier proteins
  • Moves substances like polar molecules (e.g., water) and ions (e.g., salts) down their concentration gradient
  • Direction is from high to low concentration
  • Does not require energy, but proteins are necessary

• Protein Pump

  • Active transport via carrier proteins using energy
  • Moves substances against their concentration gradient from low to high concentration
  • Energy and proteins are required

• Receptor Mediated Endocytosis

  • Active transport mechanism involving receptor proteins
  • Specific substances bind to receptors, triggering endocytosis
  • Direction of movement from low to high concentration
  • Requires energy and proteins

• Phagocytosis

  • Active transport process also known as "cell-eating"
  • Cells engulf solid materials using vesicles
  • Movement is from low to high concentration
  • Energy required, but proteins are not needed

• Pinocytosis

  • Active transport process also known as "cell-drinking"
  • Cells take in liquids via vesicles
  • Direction of transport is from low to high concentration
  • Requires energy without the need for proteins

• Exocytosis

  • Active transport mechanism for expelling substances
  • Waste and hormones are secreted from the cell
  • Movement occurs from low to high concentration
  • Requires energy but no proteins are needed