Difference between Active Transport and Passive Transport

Active transport and passive transport are two fundamental mechanisms by which substances move across cell membranes, but they operate in different ways:

 

1. Passive Transport:

   • Definition: Passive transport is the movement of substances across a cell membrane without the use of energy (ATP). It occurs spontaneously, driven by a concentration gradient.
   • Types:
     • Diffusion: The movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached. It can occur through the lipid bilayer (simple diffusion) or through protein channels (facilitated diffusion).
     • Osmosis: The diffusion of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.
   • Energy Requirement: No energy input is required.
   • Direction of Movement: From areas of high concentration to areas of low concentration (down the concentration gradient).

2. Active Transport:

   • Definition: Active transport is the movement of substances across a cell membrane against their concentration gradient, requiring the expenditure of energy (usually in the form of ATP).
   • Types:
     • Primary Active Transport: Involves the direct use of ATP to move molecules across a membrane, often against their concentration gradient. Examples include the sodium-potassium pump.
     • Secondary Active Transport: Utilizes the energy stored in the electrochemical gradient of one molecule (established by primary active transport) to drive the transport of another molecule against its concentration gradient. Examples include the sodium-glucose cotransporter.
   • Energy Requirement: Energy (ATP) is required.
   • Direction of Movement: From areas of low concentration to areas of high concentration (against the concentration gradient).

 

In summary, the key differences between active and passive transport lie in their energy requirements and the direction of movement relative to the concentration gradient. Passive transport occurs spontaneously, driven by the concentration gradient and without energy input, while active transport requires energy to move substances against their concentration gradient.

 

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