The document discusses facilitated diffusion, a process where large polar molecules and ions pass through protein channels in the cell membrane rather than diffusing directly through the phospholipid bilayer. It notes that facilitated diffusion, like ordinary diffusion, is a passive process where molecules move from high to low concentration through protein channels. It also describes the two major types of integral membrane proteins involved - carrier proteins that bind and release specific solutes, and ion channels that contain gates to control permeability and allow ion currents across the membrane without binding.

2. SUBMITTED TO:
Dr. FEROZA WATTOO
SUBMITTED BY:
WAQAS NAWAZ 11-arid-975
ZAHID NAZIR 11-arid-976
ZEESHAN AHMED 11-arid-978

3. BIOCHEMISTRY-101

4.  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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5.  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.

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7. Cell membrane
Protein channel
Inside cell Outside cell
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Transport 7

8. Cell membrane
diffusion
Protein channel
Inside cell Outside cell
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Transport 8

9. Cell membrane
diffusion
Protein channel
Inside cell Outside cell
EQUILIBRIUM
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Transport 9

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Transport 10

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Transport 11

12. 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

13.  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

14.  Not really bind the solute
 Faster than by carrier proteins
 Contain a "gate" which is functions to control
the channel's permiability