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Passive Transport. Section 5-1. Objectives. Understand what a cell membrane, cell wall, and vacuole do for a cell Be able to explain the movement of substances and water across a membrane Differentiate between passive diffusion and active diffusion. Vocabulary. Carrier protein
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Passive Transport Section 5-1
Objectives • Understand what a cell membrane, cell wall, and vacuole do for a cell • Be able to explain the movement of substances and water across a membrane • Differentiate between passive diffusion and active diffusion
Vocabulary • Carrier protein • Concentration gradient • Contractile vacuole • Cytolysis • Diffusion • Equilibrium • Facilitated diffusion • Hypertonic • Hypotonic • Ion channel • Isotonic • Osmosis • Passive transport • Plasmolysis • Turgor pressure
Diffusion • Diffusion is movement from high concentrations to low • Driven by the kinetic energy of the molecules • Passive transport doesn’t use energy • Concentration gradient is the difference in the concentration across space
Equilibrium • Concentration is the same throughout • Solutions move to equilibrium • Even at equilibrium, molecules are still moving • Movement in many directions balances
Diffusion Across Membranes • Some molecules can move from high concentration to low • Depends on size, shape, and nature • Molecules that dissolve in lipids can move across the membrane • Molecules that don’t must move through the pores
Osmosis • Water moving across a membrane • Hypotonic is when the concentration outside is lower (water moves in) • Hypertonic is when the concentration of solute is higher outside (water moves out) • Isotonic is when concentrations are equal
Osmosis in Cells • Hypotonic environment • Contractile vacuole- collects water and pumps out • Plants use cell wall- holds up against turgor pressure (the pressure water exerts) • Cytolysis (bursting) in red blood cells • Hypertonic environment • Pumps solutes out of cytosol • Plant cell membrane shrinks against cell wall (plasmolysis), plant wilts • Red blood cells shrink and shrivel
Plants Hypotonic environment Hypertonic environment
Facilitated Diffusion • Carrier proteins help some molecules • Still diffusion because moving from high to low • Molecule binds to protein, shields it from the hydrophobic cell membrane, and releases to other side of the cell • Carrier molecule is specific to molecule • Example: glucose
Ion Channels • Provide passage for ions that can’t diffuse on their own (not soluble) • Specific to each ion • Some are always open but some have gates that respond to: • Stretching of cell membrane • Electrical signals • Chemicals in cytosol or environment
Active Transport Section 5-2
Vocabulary • Active transport • Endocytosis • Exocytosis • Phagocyte • Phagocytosis • Pinocytosis • Sodium-potassium pump • Vesicle
Sodium Potassium Pump • Same as passive transport but from low to high • NA+ binds to a carrier protein from inside • Phosphate from ATP changes shape of the protein • New shape allows K+ to bind to protein (outside) and phosphate leaves • Loss of phosphate changes shape again and K+ is released into the cell • Inside becomes negative while outside becomes positive- • conducts electrical impulses
Endocytosis • Cells ingest external fluid, macromolecules, and large cells • Materials enclosed by cell and pinched off into a vesicle • Can fuse with organelles and digested • Pinocytosis is fluid • Phagocytosis is large particles • Phagocytes ingest bacteria and viruses ( • destroyed by lysozymes
Exocytosis • The reverse of endocytosis • Vesicles fuse with cell membrane and contents are released into the environment • Used to export large molecules such as proteins
