Osmosis | Forum

I've been learning plasma membrane for the pass few classes of biology.
Today learned about osmosis.

Osmosis is the movement of water molecules from a region of high water potential to a region of low water potential through a partially permeable membrane.

What is Water Potential,Ѱ? Water potential uses the symbol Ѱ. (read as 'psi')
Water potential is the measurement of free kinetic energy of water molecules.
When we have a pure water in standard temperature(25*C) and pressure(1atm) which has no impurity inside, the Ѱ is 0kPa.(Ѱ can be 0 or less than 0 only, it cant be +ve)
When we add solute(impurity) inside a pure water, the water potential will decrease to a negative value depending of the value of Solute potential Ѱ(s).[always negative]
Solute potential, Ѱ(s) is the lowering of Ѱ due to the present of solute inside the water molecules.
Therefore, Ѱ=Ѱ(s).
Why the Ѱ will be lowered when a solute is added in?
This is because the water molecules is used to dissolve the solute particles and therefore there is less free kinetic energy in the water molecules.So, Ѱ decreases.

Next, is about Pressure Potential Ѱ(p).
Ѱ(p) exist in plant cells only cause only plant cells have cell wall, which exert pressure on the water molecules when the plant cell is turgid. When a plant cell is turgid, the cytoplasm will press against the cell wall and the cell wall will press back the cytoplasm to counter it. The pressing back of the cell wall to the cytoplasm exert Ѱ(p).(This part i think i miss out something, but cant think of what is it..swt)

Ѱ, Ѱ(s) and Ѱ(p) is related by an equation : Ѱ=Ѱ(s)+Ѱ(p).
This is important in calculating Ѱ at equilibrium and to see the net water movement of one cell to the another.

Another new thing is incipient plasmolysis. We know that plasmolysis is the shrinking away of cytoplasm from the cell wall when there is lack of water in the plant cell. The plant will becomes flaccid and eventually wilt. But what is incipient plasmolysis?
Incipient plasmolysis is the point when cytoplasm starts to pull away from plant cell wall.
In other words, when the cell wall started to exert no Ѱ(p) to the cytoplasm, incipient plasmolysis is occurred. Full plasmolysis is reach when cytoplasm is completely withdrawn from the cell wall.
Besides, today I only know that where is the inside of cell. Plasma membrane is the real boundary of a cell, not the cell wall! So, inside a cell is referring to everything inside the plasma membrane. The region between the plasma membrane and the cell wall (if the cell is plasmolysed) is not considered as the inside of cell.

Next, active transport.
Active transport is the movement of ions/polar molecules through a carrier/channel protein against their concentration gradient by using energy in the form of ATP.
I forgot the detail already, cause half way learning this Mr Low came in the class and given a 'speech' to us. After the speech no time to finish the explaination so I also forgot already..but will continue next week. Haha..so active transport for next week ba.~!
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Just now created another new forum for Boon Oong. Actually last time create forum before with wei lun de, but after some time it just dead~.. This time Boon Oong will be the admin for the forum and I'll be the vice admin to help him out. The forum is under construction, but after it is done then I'll post the forum address here, in my msn personal message, friendste...haha.. And hope everyone can join to support this forum!