(7 th ) Chapter 3-4 Cornell Notes The Cell in its Environment

Chapter 3-4: Key Questions: How do most small molecules cross the cell membrane? Answer 1: Diffusion is the main method by which small molecules move across the cell membrane. Why is osmosis important to cells? Answer 1: Because cells cannot function properly without adequate water, many cellular processes depend on osmosis. What is the difference between passive transport and active transport? Answer 1: Active transport requires the cell to use its own energy, while passive transport does not.

Chapter 3-4: Key Terms selectively permeable- diffusion- osmosis- passive transport- active transport-

Chapter 3-4 Part 1 selectively permeable: some things pass through, some don’t; examples: oxygen, food particles, waste products; 3 methods to pass through: diffusion, osmosis, active transport.

Chapter 3-4 Part 2 diffusion: major method passing through; substances move from higher concentration area to a lower concentration area; caused by molecules colliding; goes into cell if more outside cell than inside.

Chapter 3-4 Part 3 very important for cells; osmosis: diffusion of water through selectively permeable membrane; water moves in if cells dehydrated.

Osmosis

Chapter 3-4 Part 4 passive transport: movement through membrane w/out using E; active transport: movement through membrane using E; case where higher concentration inside than outside cell; 1 st method: transport proteins “pick up” molecules outside and bring them in; 2 nd method: “engulfing” where cell membrane wraps or engulfs around a molecule into a vacuole.

Chapter 3-4 Part 5 most cells very small; all materials move in/out through cell membrane; cytoplasm streams carries materials inside cell; larger the cell/further to travel; that’s why cells are small.