Transport Across the Plasma Membrane

Transport Across the Plasma Membrane

• Cells require a system to allow materials to enter and exit.
• Two main types: Passive Transport and Active Transport

Passive Transport

• No energy required
• Substances move down a concentration gradient, from an area of high concentration to an area of low concentration.
• Examples of Passive Transport:
  • Diffusion: The movement of molecules from an area of high concentration to an area of low concentration.
  • Facilitated Diffusion: The movement of molecules across a membrane with the help of transport proteins.
  • Osmosis: The movement of water across a semi-permeable membrane from an area of high water concentration to an area of low water concentration.

Active Transport

• Requires energy input
• Energy is in the form of ATP
• Moves ions against their concentration gradient
• Types of Active Transport
  • Primary Active Transport: Directly uses ATP to move substances across the membrane.
  • Secondary Active Transport: Uses the energy stored in the concentration gradient of one substance to move another substance across the membrane.
  • Bulk Transport: The movement of large molecules across the membrane by endocytosis or exocytosis.
    • Antiport: Two substances move across the membrane in opposite directions
    • Symport: Two substances move across the membrane in the same direction.