What Is Facilitated Diffusion MCQ - Practice Questions & Answers

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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.