Cell Membrane Permeability and Diffusion

This page explores the concepts of membrane permeability, diffusion, and osmosis, which are crucial for understanding cell structure and function.

Definition: Permeable means allowing something to pass through, like a sponge is permeable to water.

Vocabulary: Cell membranes are selectively permeable, meaning they allow only certain substances to pass through.

The text explains diffusion as the movement of particles from areas of high concentration to low concentration. It provides a formula for the rate of diffusion:

Rate of diffusion = (Surface area × Concentration) ÷ Thickness of membrane

Definition: Osmosis is defined as the diffusion of water across a selectively permeable membrane.

The guide introduces three important terms related to osmosis:

1. Isotonic: When the concentration of solutes around a cell is the same as inside the cell, no osmosis occurs.
2. Hypotonic: When the concentration of solutes around a cell is greater than inside the cell, water diffuses out of the cell.
3. Hypertonic: When the concentration of solutes around a cell is less than inside the cell, water diffuses into the cell.

These concepts are essential for understanding osmosis and diffusion in biology notes and are frequently tested in GCSE Biology microscopy exam questions.

Osmosis in Plant Cells

This final section focuses on the effects of osmosis in plant cells, providing a visual representation of the process.

The diagram illustrates how a plant cell responds to water absorption through osmosis:

1. The cell absorbs water by osmosis.
2. The cytoplasm and cell membrane expand.
3. The cell wall prevents further expansion, creating turgor pressure.

Highlight: The rigid cell wall of plant cells plays a crucial role in maintaining cell shape and preventing bursting when water enters the cell through osmosis.

This process of turgor pressure is essential for plant structure and function, helping plants maintain their upright posture and rigidity.

Understanding osmosis in plant cells is crucial for topics such as cell structure and function Notes and Understanding osmosis and diffusion in biology class 12. It also helps in comprehending the difference between osmosis and diffusion in tabular form, as it showcases a specific application of osmosis in biological systems.

This visual explanation complements the theoretical knowledge provided earlier, offering a comprehensive understanding of osmosis and its effects on plant cells.