active transport

Active Transport Overview

• Active transport is a crucial mechanism in cellular physiology.

• It requires energy, typically in the form of adenosine triphosphate (ATP).

Types of Transport

Passive Transport

• Movement of substances across cell membranes without energy expenditure.

• Substances move from areas of high concentration to areas of low concentration (down their concentration gradient).

Active Transport

• Requires energy to move substances against their concentration gradient (from low to high concentration).

• Two key types:

  • Primary Active Transport: Directly uses ATP to transport molecules.

  • Secondary Active Transport (Cotransport): Utilizes the energy created by the primary active transport of other ions.

Comparison of Transport Mechanisms

• Passive Transport:

  • Does not require energy.

  • Movement is spontaneous and follows the concentration gradient.

• Active Transport:

  • Requires energy input (ATP).

  • Movement is against the concentration gradient.

Example in Physiology

Facilitated Diffusion

• A specific example of facilitated movement into the cell.

• Involves the use of carrier proteins to help molecules that cannot directly diffuse across the membrane due to size or polarity.

• Example: The transport of glucose into cells via glucose transporters (GLUT) which help to facilitate and ensure efficient cellular uptake.

Everyday Analogy for Active Transport

• An analogy for understanding active transport:

  • Imagine a water wheel where water is being elevated against gravity. This illustrates how active transport requires work (energy) to move molecules against their natural tendency to flow down gradients.