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7-3 Movement through the Membrane A. The cell membrane is semipermeable - only certain molecules can get through B. Passive transport: no energy required.

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Presentation on theme: "7-3 Movement through the Membrane A. The cell membrane is semipermeable - only certain molecules can get through B. Passive transport: no energy required."— Presentation transcript:

1 7-3 Movement through the Membrane A. The cell membrane is semipermeable - only certain molecules can get through B. Passive transport: no energy required 1. Diffusion: the movement of molecules from a region of high concentration to a region of low concentration

2 - continues until equilibrium is reached (equal concentrations on both sides of membrane)

3 - temperature affects diffusion: higher = faster -size of particles affects diffusion: smaller = faster

4 2. Osmosis: the diffusion of water across a membrane from high water concentration to low water concentration Which way will the water move? 97% water 100% water

5 97% water 90% water Which way will the water move?

6 This solution is hypertonic - water diffuses out of the cell 95% water 90% water 95% water 98% water This solution is hypotonic - water diffuses into the cell

7 This solution is isotonic - no net change 95% water

8 3. Facilitated diffusion: uses protein channels to move molecules from high concentration to low concentration C. Active Transport: energy required 1. Carrier proteins may act as pumps -example: sodium-potassium pump a. Cells continually pump potassium ions into the cell, and sodium ions out

9 b. Important for muscle contraction and nerve impulse transmission Na + K+K+

10 2. Endocytosis: materials move into cell

11 a. Pinocytosis: membrane encloses a fluid droplet and brings it inside the cell b. Phagocytosis: membrane encloses a large particle and brings it inside the cell

12 3. Exocytosis: materials move outside the cell - wastes and cell products may leave the cell this way

13 7-4 The Diversity of Cellular Life Unicellular organisms –a cell is the entire organism –Do everything you would expect from a living things –prokaryotic include bacteria – eukaryotic include algae

14 Multicellular –Organisms that contain many cells –Cells are specialized to perform particular functions within the organism –Levels of organization Cells Tissues Organs Organ systems


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