Lesson Note on Osmosis
Subject: Biology
Class: Grade 11
Duration: 45 Minutes
Curriculum: Nigerian Secondary School Curriculum (Integrated Curriculum)
Topic: Osmosis
Lesson Objectives
By the end of this lesson, students should be able to:
Define osmosis in terms of its processes and conditions.
Describe the methods used to demonstrate osmosis through experiments.
Analyze the effects of osmosis in plant and animal cells.
Discuss the practical applications of osmosis in real-world contexts.
Class Notes
1. Introduction to Osmosis
Definition Recap: Osmosis is a special type of diffusion that involves the movement of water molecules
from an area of lower solute concentration to an area of higher solute concentration through a selectively
permeable membrane.
Importance of Osmosis: It is essential for maintaining cell turgor in plants and regulates hydration in animal
cells.
2. Conditions for Osmosis
Selectively Permeable Membrane: The presence of a membrane that allows only certain molecules (like
water) to pass through while restricting others (like solutes).
Concentration Gradient: The difference in solute concentration between two sides of a membrane is crucial
for osmosis to occur.
3. Experiment: Demonstrating Osmosis
Materials Needed:
Dialysis tubing (or a semi-permeable membrane)
Beakers (2)
Distilled water
Salt solution (concentration can vary)
Weighing scale
Ruler
Timer
Iodine solution (optional for starch test)
Procedures:
Preparation of Dialysis Tubing: Soak the dialysis tubing in distilled water to make it pliable.
Filling the Dialysis Tubing:
Fill one piece of dialysis tubing with a concentrated salt solution and tie the ends securely.
Optionally, you can fill another piece with water to serve as a control.
Setting Up the Experiment:
Place the filled dialysis tubing into two separate beakers: one with distilled water and the other with a
concentrated saline solution.
Ensure that the beakers are labeled accordingly.
Observation:
Allow the setup to sit for at least 30 minutes.
Observe the changes in the appearance of the dialysis tubing versus the environment (beaker).
Data Recording:
Measure the initial and final mass of the dialysis tubing to quantify the amount of osmosis that occurred.
Note any visible changes in size, color, or texture.
Discussion:
Discuss the movement of water into and out of the dialysis tubing depending on the concentration of solutes
on either side.
Relate findings to the concept of osmosis.
4. Effects of Osmosis on Cells
In Plant Cells:
Turgidity: Osmosis helps maintain the plant's rigidity when cells take in water, creating turgor pressure.
Plasmolysis: When plant cells are placed in a hypertonic solution, water leaves the cell, causing it to shrink
away from the cell wall.
In Animal Cells:
Crenation: In hypertonic solutions, animal cells lose water and shrink.
Lysis: In hypotonic solutions, animal cells may take in too much water and burst.
5. Applications of Osmosis
Biological Processes: Essential for kidney functions, nutrient absorption in the intestines, and overall
cellular functions.
Industrial Applications: Use in food preservation (e.g., salting meat), water purification through reverse
osmosis, and in the medical field (IV solutions).
Conclusion
Review the key takeaways of the lesson, emphasizing the importance of osmosis in both biological systems
and various industries.
Encourage students to consider how osmosis affects everyday life and nature.
Assignment
Write a short essay on the impact of osmosis in maintaining the health of plant species.
Conduct a mini-research project on how osmotic processes are applied in agriculture.
Reference Resources
Biology textbooks (Nigerian Curriculum related)
Online resources on osmosis and its applications
Relevant articles from scientific journals
Teacher’s Notes
Assess student understanding through questions and answers during the experiment.
Adjust the complexity of the experiment based on students’ previous knowledge and engagement levels.
Ensure safety precautions are taken while conducting the experiment, especially when handling salt
solutions.
This lesson note provides a structured approach to understanding osmosis, integrating practical experi-
ments and theoretical concepts crucial for Grade 11 Biology according to the Nigerian curriculum.
