Osmosis and Water Potential
Osmosis and Water Potential
Year 11
Emary Venter
INTRODUCTION:
The cell is the basic unit of living things, and is made up of multiple organelles. Organelles are membrane bound subdivisions, each specialised for a specific function. This experiment looks at the Plasma Membrane, which is a semipermeable layer surrounding the cell. It’s primary job is to control what goes in and out of the cell. Molecules can move across this membrane in either an active movement or a passive movement. Active being that which requires energy and only occurs when molecules are required to move against the concentration gradient. The concentration gradient refers to the difference in the amount of solutes in the solutions of two adjacent areas. This investigation looks more into passive movement rather than active movement and even further into osmosis rather than diffusion. Osmosis is the movement of water across a semipermeable membrane and can only occur when the solute (in this case salt) cannot pass through the membrane. The water molecules move from a region of high solute concentration to an area of low solute concentration, therefore moving down the concentration gradient (refer to Figure 1). The osmotic potential of a cell is it’s capacity to loose water molecules. When the amount of solute in each solution is the same and the amount of molecules moving in and out of a solution is the same, it is known as dynamic equilibrium. When a cell is placed in a solution that is more concentrated than the cell, the cell loses water and therefore has a high osmotic potential. When a cell is placed in a solution that is less concentrated than the cell, the cell gains water and therefore has a low osmotic potential. For example; when a sponge is placed in a cup of cordial solution, the sponge will soak up the solution. In this case, the sponge is acting as the semipermeable membrane and is letting the water molecules in. This happens because the sponge is less concentrated
Year 11
Emary Venter
INTRODUCTION:
The cell is the basic unit of living things, and is made up of multiple organelles. Organelles are membrane bound subdivisions, each specialised for a specific function. This experiment looks at the Plasma Membrane, which is a semipermeable layer surrounding the cell. It’s primary job is to control what goes in and out of the cell. Molecules can move across this membrane in either an active movement or a passive movement. Active being that which requires energy and only occurs when molecules are required to move against the concentration gradient. The concentration gradient refers to the difference in the amount of solutes in the solutions of two adjacent areas. This investigation looks more into passive movement rather than active movement and even further into osmosis rather than diffusion. Osmosis is the movement of water across a semipermeable membrane and can only occur when the solute (in this case salt) cannot pass through the membrane. The water molecules move from a region of high solute concentration to an area of low solute concentration, therefore moving down the concentration gradient (refer to Figure 1). The osmotic potential of a cell is it’s capacity to loose water molecules. When the amount of solute in each solution is the same and the amount of molecules moving in and out of a solution is the same, it is known as dynamic equilibrium. When a cell is placed in a solution that is more concentrated than the cell, the cell loses water and therefore has a high osmotic potential. When a cell is placed in a solution that is less concentrated than the cell, the cell gains water and therefore has a low osmotic potential. For example; when a sponge is placed in a cup of cordial solution, the sponge will soak up the solution. In this case, the sponge is acting as the semipermeable membrane and is letting the water molecules in. This happens because the sponge is less concentrated
References: Figure 1: Movement of water molecules from areas of high solute concentration to areas of low solute concentration BIBLIOGRAPHY: Homework Help, http://www.enotes.com/homework-help/osmosis-diffusion-101781, date viewed: 02/03/13 Living a Salty Life, http://www.lucasbrouwers.nl/blog/2009/11/living-a-salty-life/, date viewed: 10/03/13 Osmosis and The Water Potential of a Potato, http://biology.clemson.edu/bpc/bp/lab/110/osmosis.htm, Robert. J. Koninski, last update: October 2012, date viewed: 04/03/13 Potato in Osmosis Core, http://biology.clemson.edu/bpc/bp/Lab/110/handouts/Potato%20Osmosis%20OMP.pdf, date viewed: 02/03/13