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
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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