Active Transport

Active Transport Overview

  • Movement of chemicals within a cell occurs in accordance with concentration gradients.
    • Process can involve moving substances from an area of low concentration to an area of high concentration.
    • This process is termed active transport, as it necessitates cellular energy (ATP) to proceed against the natural flow of particles, usually from high to low concentration.

Definition of Active Transport

  • Active Transport: A cellular process that utilizes energy to move substances across a membrane against their concentration gradient.
  • Movement occurs from the side where concentration is lower (low concentration) to the side where concentration is higher (high concentration).
  • Active transport requires effort and energy, specifically in the form of ATP (adenosine triphosphate).

Mechanism of Active Transport

  • In active transport, specific protein channels called pumps facilitate the movement of chemicals across the cell membrane.
  • Pumps: Specialized protein structures embedded in the cell membrane that aid in moving substances from low to high concentration.
    • Example: An active transport pump may move sodium ions (Na+Na^+) from inside the cell, where there is a higher concentration, to the outside, where there is lower concentration, using ATP as the energy source.

Types of Active Transport Processes

  • Active transport can involve various forms, including:
    • Endocytosis: The process through which a cell engulfs material from the outside environment by engulfing it with its membrane, forming a bubble (vesicle).
    • Types of endocytosis include:
    • Pinocytosis: A form of endocytosis where the cell takes in extracellular fluid (liquid) by forming small vesicles.
    • Phagocytosis: A type of endocytosis in which solid particles (e.g., food, pathogens) are engulfed by the cell and transported within a vesicle.
    • Exocytosis: The process whereby a cell expels material to the outside via vesicles formed from the membrane.
    • The prefix 'exo' means "outside," indicating that this process is centered on moving substances out of the cell.