facilitated diffusion
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Dr.Waqas Nawaz PMAS arid agriculture university rawalpindiTRANSCRIPT
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Facilitated diffusion
BIOCHEMISTRY-101
Facilitated diffusion Large polar molecules such as
glucose and amino acids, cannot diffuse across the phospholipid bilayer. Also ions such as Na+ or Cl- cannot pass.
These molecules pass through protein channels instead. Diffusion through these channels is called FACILITATED DIFFUSION.
Movement of molecules is still PASSIVE just like ordinary diffusion, the only difference is, the molecules go through a protein channel instead of passing between the phospholipids.
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Gas exchange at the alveoli — oxygen from air to
blood, carbon dioxide from blood to air. Gas exchange for photosynthesis — carbon dioxide
from air to leaf, oxygen from leaf to air. Gas exchange for respiration — oxygen from blood to
tissue cells, carbon dioxide in opposite direction. Transfer of transmitter substance — acetylcholine
from presynaptic to postsynaptic membrane at a synapse.
Osmosis — diffusion of water through a semipermeable membrane.
Major Examples Of Diffusion
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Facilitated Diffusion through a membrane
Cell membrane
Inside cell Outside cell
Protein channel
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Facilitated Diffusion through a membrane
Cell membrane
Inside cell Outside cell
Protein channel
diffusion
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Facilitated Diffusion through a membrane
Cell membrane
Inside cell Outside cell
Protein channel
diffusion
EQUILIBRIUM
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Facilitated Diffusion:Molecules will randomly move through the opening like pore, by diffusion. This requires no energy, it is a PASSIVE process. Molecules move from an area of high concentration to an area of low conc.
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Facilitated Diffusion
Two major groups of integral membrane proteins are involved in facilitated diffusion;
Carrier proteins
Ion Channels
Ion channels allow currents to be carried across the membrane and are thus of particular importance in the physiology of excitable cells like neurons
Bind a specific type of solute Discharges the solute
Certain of the hexose transporters, which transport glucose and similar monosaccharides into and out of cells
Carrier protein
Not really bind the solute Faster than by carrier proteins Contain a "gate" which is functions to
control the channel's permiability
Ion Channels
Facilitated Diffusion of Glucose
