Cell physiology: active transport — KCSE Biology

Active transport is a process that moves molecules against their concentration gradient, requiring energy, typically from ATP. In contrast, diffusion and osmosis are passive processes that do not need energy.

Key differences include:

• Energy Requirement: Active transport requires energy; diffusion and osmosis do not.
• Direction of Movement: Active transport moves substances from low to high concentration; diffusion moves from high to low, while osmosis specifically involves water.
• Transport Mechanism: Active transport often uses protein pumps; diffusion and osmosis rely on the natural movement of molecules.

Examples:

• Active Transport: Sodium-potassium pump moves Na+ ions out of cells and K+ ions in, maintaining cell potential.
• Diffusion: Oxygen diffuses from high concentration in the lungs to low concentration in the blood.
• Osmosis: Water moves from a dilute solution to a concentrated solution across a semipermeable membrane.

Active transport is a vital process in cell physiology that involves the movement of molecules against their concentration gradient, using energy in the form of ATP. This process is essential for maintaining homeostasis and enabling cells to uptake necessary substances. Key characteristics of active transport include:

• Energy Requirement: Active transport requires energy, unlike passive transport which does not.
• Transport Proteins: Specific proteins, known as pumps, facilitate this transport.
• Examples: Sodium-potassium pump and proton pump are common examples of active transport mechanisms.

The sodium-potassium pump, for instance, moves sodium ions out of the cell and potassium ions into the cell, both against their concentration gradients. This process is crucial for nerve impulse transmission and muscle contraction.

In summary, active transport is indispensable for cellular function and survival, allowing cells to absorb nutrients and expel waste efficiently.