Osmosis and Its Effects on Cells

Introduction

• Goals: By the end of this lesson, you should be able to:
  • Describe what is meant by osmosis.
  • Describe the effects of osmosis on animal and plant cells.
• Previous Topic Recap: Diffusion
  • Net movement of particles from higher concentration to lower concentration.
  • Example: Oxygen diffuses into a cell.

Definition of Osmosis

• Osmosis: Diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
• Key Points:
  • Partially permeable membrane allows some molecules (e.g., water) to pass but not others (e.g., sugar).
  • Dilute solution: High concentration of water.
  • Concentrated solution: Low concentration of water.

Basic Concepts

• Dilute Sugar Solution:
  • Contains many water molecules.
  • Scientists describe it as having a high concentration of water.
• Concentrated Sugar Solution:
  • Contains fewer water molecules.
  • Scientists describe it as having a low concentration of water.
• Water Movement:
  • Water moves from high concentration (dilute solution) to low concentration (concentrated solution) through osmosis.

Effects of Osmosis on Cells

Animal Cells

• Cytoplasm: Relatively concentrated solution (low concentration of water).
• Cell in Water:
  • Water moves into the cell by osmosis.
  • Cell expands and may burst.
• Cell in Concentrated Solution:
  • Water moves out of the cell by osmosis.
  • Cell shrinks.

Plant Cells

• Cell in Water:
  • Water moves into the cell by osmosis.
  • Cell expands but does not burst due to the cell wall.
  • The cell becomes turgid.
• Cell in Concentrated Solution:
  • Water moves out of the cell by osmosis.
  • Cell shrinks and becomes flaccid.

Conclusion

• Review the key concepts of osmosis and its effects on cells.
• Additional Resources: Practice questions available in the revision workbook linked above.