chapter seven part two

Passive Transport

• Definition: Passive transport is the movement of molecules across cell membranes without the need for energy.
• Facilitated Diffusion:
  • Definition: A form of passive transport using transport proteins to speed up the movement of molecules.
  • Mechanism:
  • Diffusion: Movement of molecules from high to low concentration.
  • Transport Proteins:
  • Two types: Channel proteins and carrier proteins.

Channel Proteins

• Definition: Membrane proteins that form tunnels or corridors, allowing specific molecules to cross the membrane.
  • Examples:
  • Aquaporins:
    • Function: Facilitate the diffusion of water.
    • Locations: Found in kidneys, assisting in the movement of water.
    • Etymology: "Aqua" refers to water, "pore" indicates a channel.
  • Ion Channels:
    • Function: Facilitate the transport of ions (charged particles).
    • Gated Channels:
    • Definition: Channels that open or close in response to a stimulus.
    • Example: In nerve cells, channels open with an electrical stimulus.
    • Action in the heart: Ion channels open in response to electrical activity, initiating a heartbeat.