Diffusion

Diffusion

Learners can:

• describe how small molecules move within and between cells

• compare and contrast diffusion and osmosis

• use a model to illustrate how substances move into and out of cells

Vocabulary: diffusion, osmosis, solute, solution, solvent

Draw

Draw what you are most excited for over winter break!

​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.

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

​Diffusion

​Is there diffusion occuring here?

​Will Diffusion happen here?

Multiple Choice

How do particles move during diffusion?

• Particles spread away from each other.

  
  

• Particles travel together in a tight clump.

  
  

• Particles move closer together.

  
  

• Particles do not move in a predictable pattern.

  
  

​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.

Multiple Choice

A semipermeable membrane separates two solutions. Which of the choices shows the direction that the water will move during osmosis?

​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.

Why diffusion is important

Diffusion helps cells:

-Get oxygen and nutrients

-Remove waste

-Stay alive without using extra energy

​The Biological Role of Osmosis

​Osmosis in Eggs?!