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Transcript
The Cell and its Environment The cell membrane is like a Gatekeeper • The cell membrane is selectively permeable, which means that some substances can pass through it while others cannot Transport in Cells • Substances that can move into and out of a cell do so by one of two methods 1) Passive Transport 2) Active Transport What is Passive Transport?? • Driven by “diffusion” natural spread of particles from and area of high concentration to low concentration • Always travels “down a concentration gradient” • Not using energy (cell doesn’t have to do anything to make it happen) BrainPOP | Passive Transport What is diffusion ? • Diffusion is a special case of passive transport by which molecules tend to move from an area of higher concentration to a area of lower concentration BrainPOP | Diffusion What is Osmosis? • The diffusion of water molecules through a selectively permeable membrane from high to low concentration is osmosis. Osmosis • Because cells cannot function properly without adequate water, many cellular processes depend on osmosis. What is Active Transport? • Active transport is the movement of materials through a cell membrane using energy from low concentration to high concentration. BrainPOP | Active Transport Active Transport • Use transport proteins • Transport proteins in the cell membrane “pickup” molecules outside the cell and carry them in using energy. Transport by Engulfing Active Transport Process by Engulfing 1) First, the cell membrane surrounds and engulfs, or encloses, a particle. 2) Once the particle is engulfed, the cell membrane wraps around the particle and forms a vacuole within the cell. **The cell must use energy in this** process. Engulfing • The main difference between passive and active transport is that active transport requires the cell to use energy while passive transport does not. • Osmosis and Diffusion are both Passive transport