Key Concepts
compare What is the difference between
passive and active transport?

Passive Transport:

1. Energy Requirement: Does not require energy (ATP) to move substances.
2. Concentration Gradient: Moves substances down their concentration gradient (from an area of higher concentration to an area of lower concentration).
3. Types: Includes simple diffusion, facilitated diffusion, and osmosis.
4. Examples:
   • Simple Diffusion: Movement of small, nonpolar molecules (e.g., oxygen, carbon dioxide) directly through the lipid bilayer.
   • Facilitated Diffusion: Movement of larger or polar molecules (e.g., glucose, ions) through specific transport proteins.
   • Osmosis: The diffusion of water across a selectively permeable membrane.

Active Transport:

1. Energy Requirement: Requires energy (usually in the form of ATP) to move substances.
2. Concentration Gradient: Moves substances against their concentration gradient (from an area of lower concentration to an area of higher concentration).
3. Types: Includes primary active transport and secondary active transport.
4. Examples:
   • Primary Active Transport: Direct use of ATP to transport molecules (e.g., sodium-potassium pump).
   • Secondary Active Transport: Uses the energy from the movement of one substance down its gradient to drive the movement of another substance against its gradient (e.g., glucose-sodium symporter).

Summary:

• Passive transport is energy-free and moves substances down their concentration gradient, while active transport requires energy and moves substances against their concentration gradient.