Content Objective: Explore the effects of water movement in plant tissues exposed to hypotonic and hypertonic solutions, including the methods for measuring changes in tissue length and mass, and the impact of water movement on cells with and without cell walls, focusing on phenomena such as turgor pressure, plasmolysis, swelling, bursting, and crenation.
Language Objective: Conduct experiments to measure and analyze changes in plant tissue in different solutions, utilizing concepts of isotonic solute concentration, standard deviation, and standard error for data analysis, and describe the cellular responses to hypotonic and hypertonic environments, including the mechanisms cells employ to maintain homeostasis in varying osmotic conditions.
Syllabus Details:
B2.1.5 - Movement of water molecules across membranes by osmosis and the role of aquaporins - "Include an explanation in terms of random movement of particles, impermeability of membranes to solutes and differences in solute concentration."
D2.3.2—Water movement from less concentrated to more concentrated solutions - "Students should express the direction of movement in terms of solute concentration, not water concentration. Students should use the terms “hypertonic”, “hypotonic” and “isotonic” to compare concentration of solutions."
D2.3.3—Water movement by osmosis into or out of cells - "Students should be able to predict the direction of net movement of water if the environment of a cell is hypotonic or hypertonic. They should understand that in an isotonic environment there is dynamic equilibrium rather than no movement of water."
D2.3.4—Changes due to water movement in plant tissue bathed in hypotonic and hypertonic solutions - "Students should be able to measure changes in tissue length and mass, and analyse data to deduce isotonic solute concentration. Students should also be able to use standard deviation and standard error to help in the analysis of data. Students are not required to memorize formulae for calculating these statistics. Standard deviation and standard error could be determined for the results of this experiment if there are repeats for each concentration. This would allow the reliability of length and mass measurements to be compared. Standard error could be shown graphically as error bars."
D2.3.5—Effects of water movement on cells that lack a cell wall -"Include swelling and bursting in a hypotonic medium, and shrinkage and crenation in a hypertonic medium. Also include the need for removal of water by contractile vacuoles in freshwater unicellular organisms and the need to maintain isotonic tissue fluid in multicellular organisms to prevent harmful changes."
D2.3.6—Effects of water movement on cells with a cell wall - "Include the development of turgor pressure in a hypotonic medium and plasmolysis in a hypertonic medium."
D2.3.7—Medical applications of isotonic solutions - "Include intravenous fluids given as part of medical treatment and bathing of organs ready for transplantation as examples."
Activity 2 - Osmosis Notes
Activity 3 - Evaluation Practice
A. Strengthen Your Skills
B. Expand Your Knowledge