facilitated diffusion Flashcards
What is facilitated diffusion?
Facilitated diffusion is a type of passive transport where ions and polar molecules move across the cell membrane through channel proteins without requiring energy.
Why can’t ions and polar molecules easily pass through the phospholipid bilayer?
Ions and polar molecules cannot easily pass through the phospholipid bilayer because the interior of the bilayer is hydrophobic, which repels hydrophilic (water-attracting) particles.
How do channel proteins facilitate diffusion?
Channel proteins are integral, transmembrane proteins with a pore that connects the cytoplasm to the outside of the cell. The diameter and chemical properties of the channels ensure that only specific particles (e.g., Na+ or K+) can pass through.
In which direction do particles move during facilitated diffusion?
Particles move from an area of higher concentration to an area of lower concentration across the membrane, which is consistent with the principles of diffusion.
Is energy required for facilitated diffusion?
No, facilitated diffusion is a passive process, meaning no energy is required for the movement of particles across the membrane.
How do cells control which substances can enter or exit through facilitated diffusion?
Cells can control which hydrophilic substances diffuse in and out by the types of channel proteins that are synthesized and placed in the plasma membrane.
Can the permeability of the cell membrane be changed during facilitated diffusion?
Yes, some channel proteins can be opened and closed, allowing the cell to temporarily change its permeability when necessary.
What is the main difference between facilitated diffusion and simple diffusion?
The main difference is that facilitated diffusion requires channel proteins to help ions and polar molecules pass through the membrane, while simple diffusion occurs directly through the phospholipid bilayer.
