1. THE CELL IN ITS ENVIRONMENT
Week 3 Notes
Ch. 1, Sect 4 Page 32 – 37

2. I. The Cell in it’s Environment
1. All __CELLS__ are surrounded by a __CELL MEMBRANE__
2. The Cell Membrane is __SELECTIVELY PERMEABLE__, which means that __SOME__ substances can __PASS__ through the membrane while other cannot.
3. __OXYGEN__ and __FOOD__ must __ENTER__ the cell,
4. __WASTE__ must __LEAVE__ the cell

3. A. 3 ways to enter the cell: __DIFFUSION__, __OSMOSIS__, or __ACTIVE TRANSPORT__

4. II. DIFFUSION
1. __DIFFUSION__ is the __MAIN__ method by which small __MOLECULES__ move __ACROSS__ the cell membrane.
2. Diffusion is the process by which molecules __MOVE__ from an area of __HIGHER CONCENTRATION__ to an area of __LOWER__ concentration.

5. A. What Causes Diffusion
1. __MOLECULES__ are always moving.
2. The __MORE__ molecules the __MORE__ collisions
3. The __COLLISIONS__ cause molecules to push away from one another until they are spread out __EVENLY__
BrainPop – Diffusion (3:10)

6. III. OSMOSIS
1. __OSMOSIS__ is the __DIFFUSION__ of __WATER__ molecules through a selectively permeable membrane.
A. Effects of Osmosis
1. __NORMAL__ blood Cell __CONCENTRATION__ of water inside the cell is the __SAME__ outside
2. __LOW__ water concentration outside of cell __WATER__ moves out of the __CELL__ during __OSMOSIS__
3. __HIGH__ water concentration outside cell during __OSMOSIS__, __WATER__ moves into the cell
BrainPop: Passive Transport (3:03)

7. IV. ACTIVE TRANSFER
1. __OSMOSIS__ and __DIFFUSION__ does __NOT__ take __ENERGY__ from the cell 2. Movement of materials through a __CELL MEMBRANE__ without using cellular __ENERGY__ is called __PASSIVE TRANSPORT__ 3. __ACTIVE TRANSPORT__ is the movement of materials through a cell membrane __USING__ cellular __ENERGY__.

8. A. Transport Proteins
1. __TRANSPORT__ proteins in the cell membrane “__PICK UP__” molecules outside the cell and __CARRY__ them into the cell using __ENERGY__

9. B. Transport by Engulfing
1. The Cell Membrane __SURROUNDS__ and engulfs, or __ENCLOSES__, a particle. Once the particle is __ENGULFED__, the cell membrane ___WRAPS__ around the particle and __CREATES__ a __VACOULE__ within the cell.
Brain Pop – Active Transport (3:04)

10. C. Why Cells are Small
1. What prevents cells from growing very large?