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What Is Facilitated Diffusion - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET

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Facilitated Diffusion
  • The cell membrane is made up of lipids and proteins. 
  • Particles that are soluble in lipids, that is, lipophilic particles find it easier to diffuse across the plasma membrane.
  • Their diffusion is said to be simple diffusion, which is entirely driven by the concentration gradient.
  • Hydrophobic substances like mineral ions, glucose, water, etc. face a repulsion by the lipid bilayer.
  • These substances need a facility to diffuse across the membrane despite have a concentration gradient.
  • Their diffusion is therefore called facilitated diffusion.
  • Facilitated diffusion does not require energy (ATP utilization) because the movement of particles occurs down the concentration gradient.
  • Some specialised proteins called porins and channels are used to facilitate the movement of hydrophilic substances across the plasma membrane down their concentration gradient.
  • Facilitated diffusion never causes a net movement of particles from the region of their lower concentration to the region of their higher concentration.
  • Transport rate reaches a maximum when all the protein transporters are saturated.
  • Some channel proteins are always open, such as aquaporins for water transport.
  • Other channel proteins can be controlled.
  • Porins are pore-forming proteins present in the outer membranes of plastids, mitochondria and some bacteria.
  • Porins allow large molecules to pass through the cell membrane.


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