Selectively Permeable Cell MembranePhospholipid bilayer Chapter 3 4
+ Selectively Permeable Cell Membrane(Phospholipid bilayer) Chapter 3. 4: “Diffusion and Osmosis” KEY CONCEPT Materials move across membranes because of concentration differences.
Chapter 3. 4: “Diffusion and Osmosis” Molecules can move across the cell membrane through passive transport. • Passive transport does not require energy input from a cell. • There are two types of passive transport: 1. Diffusion 2. Osmosis
Chapter 3. 4: “Diffusion and Osmosis” Diffusion and osmosis are types of passive transport. • Diffusion: molecules diffuse down a concentration gradient (high low) Diffusion High Concentration Equilibrium: No net movement (amount entering = amount leaving) Low Concentration
Chapter 3. 4: “Diffusion and Osmosis” Some molecules ( ie: glucose and sodium) cannot easily diffuse across the cell membrane • Some molecules can only diffuse through transport proteins. • Facilitated diffusion is diffusion through transport proteins (still doesn’t require energy) Channel Protein
Chapter 3. 4: “Diffusion and Osmosis” Diffusion and osmosis are types of passive transport. • Osmosis is the diffusion of water molecules across a semipermeable membrane. High Low Equilibrium
Chapter 3. 4: “Diffusion and Osmosis” Diffusion and osmosis are types of passive transport. • There are three types of solutions. 1. Isotonic: solution has same concentration of solutes as the cell 2. Hypertonic: has more solutes than the cell 3. Hypotonic: solution has fewer solutes than the cell
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