#activestrasport #biolody #textbook #igcse

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Active transport:

• Energy Requirement: Active transport requires energy (usually ATP) because it moves substances against their natural concentration gradient.

• Transport Proteins: It relies on specialized proteins embedded in the cell membrane, such as pumps and carrier proteins, that facilitate the movement of specific molecules.

• Examples:

  • Sodium-Potassium Pump: This pump moves sodium ions (Na⁺) out of the cell and potassium ions (K⁺) into the cell, both against their concentration gradients, helping maintain proper ion balance and cell function.

  • Calcium Pump: Actively moves calcium ions (Ca²⁺) into storage compartments within cells, crucial for muscle contractions and cell signaling.

Types of active transport:

Active transport can be divided into two main types:

• Primary Active Transport: Uses energy directly from ATP to move molecules across a membrane. An example is the sodium-potassium pump, where ATP hydrolysis provides the energy to move ions against their gradients.

• Secondary Active Transport (Cotransport): Uses the energy generated from moving one molecule down its concentration gradient to drive another molecule against its gradient. For example, glucose and sodium ions can be cotransported into cells, with sodium moving along its gradient to power glucose uptake against its gradient.

Difference with diffusion:

• Energy Use: The primary difference is that active transport needs cellular energy (ATP) because it moves molecules "uphill," or from lower to higher concentration. Diffusion, on the other hand, is passive and does not require energy, as molecules naturally move "downhill" from higher to lower concentration.

• Movement Direction: In diffusion, molecules move freely from an area of high concentration to low concentration. In active transport, the cell moves molecules in the opposite direction, from low to high concentration, allowing cells to absorb needed nutrients or expel waste even against gradients.

• Protein Involvement: Active transport always involves specific proteins like pumps or carriers to move molecules, whereas diffusion may not involve proteins (e.g., simple diffusion of gases) unless it's facilitated diffusion, which still does not require ATP.

Importance of active transport:

Active transport is essential for maintaining concentration gradients of ions and molecules within cells, crucial for physiological functions such as:

• Nerve Function: The sodium-potassium pump helps maintain the electrochemical gradient required for nerve impulse transmission.

• Muscle Contraction: Calcium ions are pumped into muscle cells, allowing for regulated contraction and relaxation.

• Nutrient Absorption: In the intestines, active transport absorbs glucose and amino acids against their concentration gradients, ensuring adequate nutrient uptake.

active transport is a process that allows cells to maintain necessary concentrations of ions and molecules against gradients by using energy, while diffusion is a passive process that balances concentrations by moving molecules along their gradients without energy input. Both processes are vital to cellular function and homeostasis in the body.