Osmosis and Concentration Gradients

This page delves deeper into the concepts of diffusion and osmosis, focusing on concentration gradients and their effects.

The page begins by explaining how the concentration gradient affects diffusion rates. It emphasizes that diffusion occurs down the concentration gradient, from areas of high concentration to low concentration.

Highlight: The bigger the difference in concentration, the steeper the concentration gradient and the faster the rate of diffusion.

An example of diffusion in respiration is provided:

Example: Oxygen needed for respiration passes from the air in lungs into red blood cells through cell membranes by diffusion, moving down the concentration gradient from high to low oxygen concentration.

The page then transitions to discussing osmosis, introducing key terminology:

Vocabulary: A dilute solution contains a high concentration of solvent (e.g., water) and a low concentration of solute (e.g., sugar). A concentrated solution has the opposite composition.

The fundamental principle of osmosis is explained:

Definition: In osmosis, water moves from a dilute solution (high concentration of water molecules) to a concentrated solution (fewer water molecules in a given volume) across the membrane of a cell.

This information provides a solid foundation for understanding the mechanisms of diffusion and osmosis in cells.

Effects of Osmosis on Cells

This page explores the effects of osmosis on animal cells in different types of solutions. It introduces key terminology related to solution tonicity and illustrates the cellular responses.

Three types of solutions are defined:

Definition:

• Isotonic solution: The concentration of solutes outside the cell is the same as inside.
• Hypertonic solution: The concentration of solutes outside the cell is higher than inside.
• Hypotonic solution: The concentration of solutes outside the cell is lower than inside.

The page then describes how cells react in each type of solution:

1. In an isotonic solution, the cell remains normal.
2. In a hypertonic solution, water moves out of the cell by osmosis, causing it to shrivel.
3. In a hypotonic solution, water moves into the cell by osmosis, causing it to swell and potentially burst.

Highlight: If the solution outside the cell becomes much more concentrated (hypertonic) than the cell contents, water will move out of the cell by osmosis. The cytoplasm will become too concentrated, and the cell will shrink/shrivel up and can no longer survive.

This information is crucial for understanding how osmosis affects cells in different environments and is particularly relevant for topics like diffusion and osmosis in cells GCSE.

Diffusion and Osmosis Fundamentals

This page introduces the key concepts of diffusion and osmosis in biology.

Diffusion is defined as the movement of particles from an area of high concentration to low concentration. Osmosis specifically refers to the movement of water molecules across a semi-permeable membrane from high to low concentration areas. The page also mentions active transport, which uses energy to move particles against the concentration gradient.

Definition: Diffusion is the movement of particles from an area of high concentration to low concentration.

Definition: Osmosis is the movement of water particles from an area of high concentration to low concentration via a semi-permeable membrane.

The page provides examples of diffusion in biological systems:

Example: Diffusion examples in the human body include gas exchange in lungs and nutrient absorption in small intestines. In plants, diffusion of carbon dioxide into leaves occurs during photosynthesis.

Factors affecting the rate of diffusion are listed, including concentration gradient, temperature, distance, molecule size, and surface area. The concentration gradient is highlighted as a key factor.

Highlight: The difference between two areas of concentration is called the concentration gradient. The steeper the gradient, the faster the rate of diffusion.