diffusion
diffusion = passive transport
passive transport : it's means random molecular movement through the cell membrane or in combination with carrier protein from areas of high concentration to area of low concentration by the aid of the kinetic energy of molecules .
a molecule can diffuse through the membrane is :
1. lipid soluble e.g. oxygen and carbon dioxide .
2. small enough to pass through membrane channels .
3. assisted by a carrier molecule e.g. glucose and aminoacid .
Type Of Diffusion :
I. simple diffusion :
1. The Lipid bilayer Of The Cell membrane .
e.g. O2 , CO2 .
Fat solube vitamins .
Non-Polar .
Lipid Soluble .
2. Channel protein of the cell membrane .
e.g. water .
water-soluble substance .
They are Two Type :
1. Continuously opened ( Leak Channels ) .
2. Channels controlled By gates that can be opened or closed by various chemicals or electrical signals .
II. Facillitated diffuion : or called (carrier - mediated diffusion)
why ?
because the transported substance uses a specific carrier protein most probably lipo protein molecular .
a. Mechanism :
the substance at the outerside of the lipld membrane through the membrane . where it splits at its inner side .
The absorbed substance passed to ward The Cytoplasm and the carrier to ward the outer surface of the membrane .
b.What are The substance Can be transport by facilitated ?
1. Large sized molecular .
2. Lipid insoluble molecular .
3. Polar molecular such as sugars aminoacids .
why ?
because the transported substance uses a specific carrier protein most probably lipo protein molecular .
a. Mechanism :
the substance at the outerside of the lipld membrane through the membrane . where it splits at its inner side .
The absorbed substance passed to ward The Cytoplasm and the carrier to ward the outer surface of the membrane .
b.What are The substance Can be transport by facilitated ?
1. Large sized molecular .
2. Lipid insoluble molecular .
3. Polar molecular such as sugars aminoacids .
c. Facilitated diffusion depends on :
1. The availability of the Carrier .
2.High Concentration gradient of the substance through The membrane .
3. rapid combination and splitting of the carrier with the transported substance .
4. saturation of the carrier .
Factors affecting the rate of diffusion :
1. Surface area of the membrane: The greater the surface area of the membrane the higher the rate of diffusion.
2. Concentration gradient: Greater concentration difference of the substance on both sides of the membrane increases the rate of diffusion.
3. Pressure gradient : The higher the difference in pressure of the substance on both sides of the membrane, the more the rate of diffusion.
4. Electric gradient : lons pass from positively charged medium to negatively charged one even if there is no concentration difference.
5. Permeability of the membrane: the rate of diffusion increases by increasing the permeability of the membrane.
1. The availability of the Carrier .
2.High Concentration gradient of the substance through The membrane .
3. rapid combination and splitting of the carrier with the transported substance .
4. saturation of the carrier .
Factors affecting the rate of diffusion :
1. Surface area of the membrane: The greater the surface area of the membrane the higher the rate of diffusion.
2. Concentration gradient: Greater concentration difference of the substance on both sides of the membrane increases the rate of diffusion.
3. Pressure gradient : The higher the difference in pressure of the substance on both sides of the membrane, the more the rate of diffusion.
4. Electric gradient : lons pass from positively charged medium to negatively charged one even if there is no concentration difference.
5. Permeability of the membrane: the rate of diffusion increases by increasing the permeability of the membrane.
By : Supervised by :
Ammar Mohammed Dr. Mona Mostafa
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