Cells - Transport across membranes: Osmosis Flashcards
Define osmosis
The passage of water from a region where it has a higher water potential to a region where it has a lower water potential through a selectively permeable membrane.
What kind of transport is osmosis?
Passive transport
What is a solute?
Any substance that is dissolved in a solvent.
An example of a solvent
Water
What do a solvent and a solute form?
A solution
What letter is osmosis represented by?
psi (looks like a trident)
What is water potential?
The pressure created by water molecules
Units of water potential
kPa (kilo Pascals)
What is the water potential of pure water?
Zero
How will the addition of a solute to pure water affect its water potential?
It will lower the water potential.
How does the concentration of a solution affect its water potential?
The more concentrated solution, the lower the water potential.
How can you find the water potential of cells or tissues?
By placing them in a series of solutions of different water potentials. Where there is no net gain or loss of water from the cells or tissues, the water potential must be the same as that of the external solution.
What will happen if an animal cell is placed in pure water?
They will absorb is by osmosis due to having a lower water potential.
What will happen to an animal cell if it is placed in a solution with a higher water potential?
The cell membranes will break, busting the cell and releasing its contents.
Why do cell surface membranes break when the cell absorbs water?
Cell surface membranes are very thin and cannot stretch to a great extent.
