Osmosis Flashcards
What is osmosis?
Osmosis is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane.
High water potential
A solution with many water molecules has a high water potential.
Low water potential
A solution with few water molecules has a low water potential.
What is a solution?
The biochemical processes in living cells always take place in a solution. A solution is a homogeneous mixture of one or more solutes dissolved in a solvent.
What is a solvent?
The substance in which the solute dissolves.
What is a solute?
The substance which dissolves in the solvent.
What is osmosis in terms of diffusion?
Osmosis is just a special case of diffusion and is specifically the diffusion of water molecules.
What is water concentration?
The amount of water, as compared to other molecules
What is concentration?
The proportion of solvent: solute
What is an isotonic solution?
An isotonic solution is equal. Iso=equal. Tonic= strength
What is a hypertonic solution?
Hyper=Above, Tonic=strength
Higher concentration of solvent inside the cell so it travels out of the cell.
What is a hypotonic solution?
Hypo= Below
Higher concentration of solute inside the cell so solvent flow into the cell.
Cells and osmosis
If a cell is placed in a solution of lower water potential, water leaves the cell by osmosis. If the cell is placed in a solution of higher water potential, water enters by osmosis.
What happens if water enters a plant cell?
If water enters a plant cell by osmosis the cytoplasm will swell, but only until it pushes against the cellulose wall.
Can the entry of water damage a plant cell?
A plant cell will not be permanently damaged by the entry of water.
What happens if water leaves a plant cell?
If water leaves a plant cell by osmosis the cytoplasm will shrink, but the cellulose cell wall will continue to give some support.
Can the loss of water damage a plant cell?
Plant cells rarely suffer damage by the loss of water.
What happens when the cell is in a solution of lower water potential than cell contents?
Water leaves by osmosis. The cytoplasm pulls away from the cell wall and the cell becomes flaccid.
Flaccid
Floppy
Cell in solution of equal water potential
No net movement of water, cytoplasm presses against cell wall
What happens when a cell is in a solution with higher water potential?
Water enters by osmosis. The cytoplasm pushes hard against the cell wall and the cell becomes turgid.
Turgid
Firm
Can osmosis damage animal cells?
Osmosis is potentially damaging to animal cells, and animals have mechanisms to keep blood plasma and the body fluids at the same water potential as the cytoplasm of cells. In mammals the kidney plays a vital part in this process of osmoregulation.
Red blood cell in a solution of lower water potential.
The cell loses water, shrinks and becomes crenated.
Crenation
The formation of uneven notched corners on cells caused by osmosis water loss
Red blood cell in a solution of the same water potential
The cell is in equilibrium.
Equilibrium
Equilibrium is the state in which all forces acting on the body are balanced with an equal and opposite force
Red blood cell in a solution of high water potential
The cell takes in water, swells and bursts. (Hemolysis)
Ghost of red blood cell
Membrane left behind
Plasmolysis
Plasmolysis is the process in which cells lose water when they are placed in a hypertonic solution.
Key points: Osmosis defintion
Osmosis is the diffusion of water from a region of higher concentration to a region of lower concentration of water through a partially permeable membrane.
Key points: types of solutions
In comparing two solutions of unequal solute concentration, the solution with the higher solute concentration is hypertonic, and the solution with the lower concentration is hypotonic. Solutions of eequal solute concentration are isotonic.
