Introduction to Osmosis and Diffusion

This page delves deeper into the mechanisms of osmosis and diffusion, explaining their differences and the role of cell membranes.

Definition: A selectively permeable cell membrane allows certain materials to pass through while keeping others out.

The page explains that water constantly passes through the cell membrane, and when the movement of water molecules in and out of a cell occurs at the same rate, a state of equilibrium is reached.

Vocabulary:

• Osmosis: The movement of water molecules from an area of high concentration to low concentration. Only the solvent (water) moves.
• Diffusion: The movement of molecules from high concentration to low concentration. Both solvent and solute move.

Example: A diagram illustrates the process of osmosis, showing water molecules moving through a semipermeable membrane from an area of low solute concentration to high solute concentration.

Highlight: The key difference between osmosis and diffusion is that in osmosis, only the solvent (water) moves, while in diffusion, both solvent and solute molecules move.

The page concludes with a visual representation of diffusion, showing how molecules eventually become evenly distributed across a membrane.

Tonicity and Osmosis

This page introduces the concept of tonicity and osmosis, focusing on the movement of water through cell membranes.

Definition: Osmosis is the process by which water moves from an area of high concentration to low concentration.

The page outlines three osmotic states:

1. Isotonic Solution: Equal concentration of water inside and outside the cell membrane. Water moves in and out at the same rate.

2. Hypotonic Solution: Less solute and more water outside the cell. Water moves into the cell through osmosis, causing it to expand or burst.

3. Hypertonic Solution: More solute and less water outside the cell. Water moves out of the cell through osmosis, causing it to shrink.

Example: A diagram illustrates the difference between hypotonic and hypertonic solutions, showing 90% water and 10% solute on both sides, but with different concentrations.

Highlight: The direction of water movement in osmosis depends on the relative concentrations of solutes inside and outside the cell.