Concept of Diffusion, Osmosis and Water Potential Flashcards
What is diffusion?
Diffusion is the movement of molecules from an area where they have a high concentration to an area where they have a low concentration down a concentration gradient.
What are semi-permeable membranes?
Membranes form the outer covering of cells and cell organelles. These membranes are termed semi-permeable membranes because only small molecules can pass through them while large molecules can’t. Semi-permeable membranes enable cells to control the exit and entry of molecules.
What is osmosis?
Osmosis is the movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient through a semi-permeable membrane.
What is water potential?
Water potential refers to the potential energy water molecules have for movement. We say that water molecules move from an area of high water potential to and area of lower water potential through a semi-permeable membrane down a water potential gradient by the process of osmosis.
What defines a high water potential?
Pure water has the highest possible water potential while water containing any dissolved substances always has a lower water potential. For example a cell contains water and dissolved substances (for example glucose sugar) and therefore has a lower water potential than that of the water surrounding the cell.
How do roots absorb water?
Soil water has a higher water potential than the water within the root hairs of the root and therefore moves into (is absorbed by) the root hair cells by the process of osmosis.
The water moves from an area of high water potential in the soil through the semi-permeable cell membrane of the root hair cell into an area of lower water potential down a water potential gradient by the process of osmosis.
What happens once the roots absorb the water?
Once inside the root hair cell, the water moves across the root cells within the root (always from an area of higher water potential to an area of lower water potential) to the centre of the root where it enters the xylem transporting tissue which transports the absorbed water to all the different parts of the plant.
What does it mean when we speak about a high concentration of molecules or ions in a solution?
A high concentration equals a high number of a particular molecule/ ion.
