Do Now 1. How are the molecules of water vapor different than the molecules of liquid water? 2. How are they different than ice? 3. What does concentration mean? Is there another definition for concentration?

Movement Chemical bonds Distance

Cell Membrane “The Cell and Its Environment”

The cell membrane is selectively permeable. This means that some substances can pass through while others cannot. It does not mean that the cell membrane has complete control.

Two ways molecules can move across the cell membrane. – Passive Transport is the movement of substances across the cell membrane without using cellular energy. Ex) diffusion, osmosis – Active Transport is the movement of substances across the cell membrane using cellular energy. Ex) transport proteins, engulfing

Passive Transport Diffusion is the process by which molecules move from an area of high concentration to an area of low concentration. Diffusion is the main method by which small molecules move across the cell membrane. Diffusion happens when molecules bump into each other and then move in opposite directions.

Think about it In which states of matter (solid, liquid and gas) would diffusion take place?

Think about it How might diffusion be related to wind or temperature of the air? Draw a quick sketch with your shoulder partner to illustrate the concept.

Osmosis is the diffusion of water through a selectively permeable membrane. – The cell membrane cannot control osmosis. – Because of osmosis, the concentration of water inside a cell will be the same as the concentration of water outside the cell.

Think about it What would happen to a cell if the concentration of water in the outside environment became much higher than the concentration of water inside the cell?

Active Transport Transport proteins are proteins in the cell membrane that use energy to move molecules in or out of the cell. Different types of transport proteins move different types of molecules.

Some cells, like an amoeba, can “engulf” substances. When this happens the substance is pushed through the cell membrane. Once inside, a vacuole will quickly form around the substance protecting the inside environment from potential harm. Enzymes can be added to turn the vacuole into a lysosome.

Think about it Why would an amoeba want to add enzymes with an engulfed substance?