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

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

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

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.

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)

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)

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__.

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

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)

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