Movement of Molecules: Passive Transport, Simple Diffusion, Facilitated Diffusion

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Passive Transport

• In Passive Transport, the transportation of molecules across the membrane is using a concentration gradient.

• Cellular energy is not required.

• The movement of biochemical is from higher to the lower concentration.

• Natural entropy is used for movement form higher to the lower concentration.

• At equilibrium there is no net transport of molecules.

• Using this process all the waste molecules using water and carbon dioxide get separated.

• This process occurs in the kidneys and the liver including the alveoli of the lungs during the exchange oxygen and carbon dioxide.

• Some of the examples of passive transport are Osmosis, diffusion and facilitated diffusion.

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Types of Passive Transport

Simple Diffusion

• There is a net movement of atoms, ions, and molecules.

• Movement is from a region of higher concentration to a region of lower concentration.

• Driven by a gradient in concentration.

• Simple diffusion is used by many non-polar molecules.

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Facilitated Diffusion

• Also known as facilitated transport or passive-mediated transport.

• Involves process of spontaneous passive transport.

• Doesn’t directly require chemical energy from ATP hydrolysis.

• The transportation is based on molecular binding.

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Osmosis

• Transportation of water and other molecules or substance.

• The transportation takes place through the selectively permeable cell membrane.

• Factors affecting this transportation:

  • Cell having less negative water potential.

  • Soluble potential of a molecule.

  • Pressure potential of a cell membrane.

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