Osmosis Flashcards
What is 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 type of membranes are selectively permeable?
Cell-surface membranes and other plasma membranes around organelles.
What is a solute?
Any substance that is dissolved in a solvent, for example, water.
What is water potential represented by?
The Greek letter psi (Ψ).
What is the water potential of pure water under standard conditions?
Zero.
What effect does adding a solute to pure water have on its water potential?
It lowers the water potential.
What is the water potential of a solution always?
Less than zero (a negative value).
How does the concentration of solute affect water potential?
The more solute that is added, the lower (more negative) its water potential.
In what direction does water move by osmosis?
From a region of higher (less negative) water potential to one of lower (more negative) water potential.
How can the water potential of cells or tissues be determined?
By placing them in a series of solutions of different water potentials until there is no net gain or loss of water.
What happens to animal cells when placed into pure water?
They may swell and potentially burst due to water influx.
What happens to plant cells when placed into pure water?
They become turgid as water enters, but the cell wall prevents bursting.
Fill in the blank: Osmosis is the movement of _______ molecules only.
water
True or False: Osmosis involves the movement of both solute and water molecules.
False.
What is the primary factor that drives osmosis?
The difference in water potential.
What is the relationship between kinetic energy and molecular movement in osmosis?
Both solute and water molecules are in random motion due to their kinetic energy.
What is the practical link mentioned for osmosis?
Production of a dilution series of a solute to produce a calibration curve for identifying the water potential of plant tissue.
What type of membrane is described as selectively permeable?
Plasma membrane
The selectively permeable plasma membrane allows certain molecules to pass while restricting others.
What molecules can cross the selectively permeable plasma membrane?
Water molecules
Solute molecules cannot pass through the selectively permeable plasma membrane.
From which side do water molecules diffuse across the plasma membrane?
From the side with higher water potential
Water molecules move to the side with lower water potential.
What is the term for the movement of water molecules from high to low water potential?
Diffusion
This movement occurs down a water potential gradient.
What occurs when the water potentials on either side of the plasma membrane are equal?
Dynamic equilibrium is established
At this point, there is no net movement of water.
Fill in the blank: Water molecules diffuse from the left-hand side, which has the higher water potential, to the right-hand side, which has the _______.
Lower water potential
True or False: The plasma membrane allows both water and solute molecules to cross.
False
The plasma membrane only permits water molecules to cross.
