The Cell in Its Environment

Mrs. Brunner

Chapter 1: 4

7th Grade

• I. The Cell in Its Environment– A. Cell Membrane – Gatekeeper

• 1. Selective Permeability – • 2. what does the cell want to let in?• 3. 3 ways materials move into and out of cells…

– a.– b.– c.

– B. Diffusion – Molecules in Motion• 1. process by which molecules move from areas…• 2. main method • 3. Remember the demonstrations? • 4. when molecules move they bump into each other• 5. over time…

– C. Osmosis – Diffusion of Water

– C. Osmosis• a. diffusion of water• b. important because all chemical reactions

take place in water• c. if too much water moves into the cells…• d. if too much water moves out of the cell…

– D. Active Transport• a. materials move into the cell

(diffusion/osmosis) without using energy – this is passive transport

• b. materials that move from inside the cell to the outside of the cell takes energy – this is active transport

• c. in other words…active transport takes materials from areas of less concentration to areas of greater concentration

– d. main difference…– e. 2 types of active transport

• 1. transport proteins – proteins in cell membrane that actually ‘pick up’ substances and carry them

• 2. engulfing – cell surrounds a material, absorbs and forms a vacuole around the substance

• E. Why are cells so small?– a. materials inside cell travel on a ‘stream’

of cytoplasm– b. if the cell was too big, the materials

would have too far to travel and cell would probably die