Diffusion Lesson

​What is the largest cell on Earth?

We'll find out at the end of class!

​Engage

​Recall that the particles in matter are in constant motion. The higher the temperature of a substance, the faster the particles move.

The matter found inside the cells of living things also constantly moves. All of the molecules inside of your body are moving right now.

​Recall that the particles in matter are in constant motion. The higher the temperature of a substance, the faster the particles move.

The matter found inside the cells of living things also constantly moves. All of the molecules inside of your body are moving right now.

​The movement of molecules causes the phenomenon that you will study in today's lesson. Continue on to learn about diffusion.

​Diffusion

​All of the particles spread from where they were the most concentrated to where they were least concentrated.

​Concentration Gradient

​How Does Diffusion Occur In Cells?

​Diffusion can happen in an open container. It can also occur through a cell membrane. Some substances can pass directly through the phospholipid bilayer. Substances can also pass through proteins in the plasma membrane that work like doorways. Continue on to learn how water moves across the cell membrane.

​Osmosis

​Osmosis is the movement of water across a cell membrane. Some of the water moves directly through the phospholipid bilayer. Osmosis through the bilayer is relatively slow because of the water-fearing tails on the phospholipids.

​Solutions

The water in your cells is not pure water. Many substances are dissolved in the water. There are three important terms to learn that relate to substances dissolved in the cell:

• solution;

• solvent; and

• solute.

​Water is the main solvent present in cells. Water moves across the cell membrane through osmosis, but many of the solutes in the water do not. When you think about osmosis, remember that osmosis involves the movement of the water, not the substances dissolved in the water.

​Osmosis plays an important role in organisms. It maintains plant cell structure, facilitates nutrient and waste exchange in all organisms, and regulates blood pressure and nutrient absorption.

​The Biological Role of Osmosis

​Osmosis in Eggs?!