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Section 1 Passive Transport Section 2 Active Transport. Chapter 5. Homeostasis and Cell Transport. Table of Contents. Explain how an equilibrium is established as a result of diffusion. Distinguish between diffusion and osmosis.
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Section 1 Passive TransportSection 2 Active TransportChapter 5Homeostasis and Cell TransportTable of ContentsExplainhow an equilibrium is established as a result of diffusion.Distinguishbetween diffusion and osmosis.Explain how substances cross the cell membrane through facilitated diffusion.Explainhow ion channels assist the diffusion of ions across the cell membrane.Section 1 Passive TransportChapter 5ObjectivesPassive transport involves the movement of molecules across the cell membrane without an input of energy by the cell.Diffusionis the movement of molecules from an area of higher concentration to an area of lower concentration, driven by the molecules’ kinetic energy until equilibrium is reached.Section 1 Passive TransportChapter 5DiffusionSection 1 Passive TransportChapter 5Concentration GradientClick below to watch the Visual Concept.Visual ConceptDiffusion Across MembranesMolecules can diffuse across a cell membrane by dissolving in the phospholipid bilayer or by passing through pores in the membrane.Section 1 Passive TransportChapter 5Diffusion, continuedSection 1 Passive TransportChapter 5DiffusionOsmosisis the diffusion of water across a membrane. Section 1 Passive TransportChapter 5OsmosisSection 1 Passive TransportChapter 5OsmosisClick below to watch the Visual Concept.Visual ConceptDirection of OsmosisThe net direction of osmosis is determined by the relative solute concentrations on the two sides of the membrane.Section 1 Passive TransportChapter 5Osmosis, continuedDirection of OsmosisWhen the solute concentration outside the cell is higher than that in the cytosol, the solution outside ishypertonicto the cytosol, and water will diffuse out of the cell.When the solute concentration outside the cell is lower than that in the cytosol, the solution outside is hypotonic to the cytosol, and water will diffuse into the cell.Section 1 Passive TransportChapter 5Osmosis, continuedDirection of OsmosisWhen the solute concentrations outside and inside the cell are equal, the solution outside isisotonic, and there will be no net movement of water.Section 1 Passive TransportChapter 5Osmosis, continuedSection 1 Passive TransportChapter 5Hypertonic, Hypotonic, Isotonic SolutionsSection 1 Passive TransportChapter 5Comparing Hypertonic, Isotonic, and Hypotonic ConditionsClick below to watch the Visual Concept.Visual ConceptHow Cells Deal With OsmosisTo remain alive, cells must compensate for the water that enters the cell in hypotonic environments and leaves the cell in hypertonic environments.Contractile vacuoles are organelles that regulate water levels in paramecia.Section 1 Passive TransportChapter 5Osmosis, continuedIn facilitated diffusion, a molecule binds to a carrier protein on one side of the cell membrane. The carrier protein then changes its shape and transports the molecule down its concentration gradient to the other side of the membrane.Section 1 Passive TransportChapter 5Facilitated DiffusionSection 1 Passive TransportChapter 5Facilitated DiffusionIon channelsare proteins, or groups of proteins, that provide small passageways across the cell membrane through which specific ions can diffuse.Each ion channel is usually specific for 1 type of ion.Some ion channels are always open.Other have gates that allow them to open/close in response to stimuli:Stretching of cell membraneElectrical signalsChemicals in cytosol/external environmentStimuli control ability of specific ions to cross cell m.Section 1 Passive TransportChapter 5Diffusion Through Ion ChannelsSection 1 Passive TransportChapter 5Ion ChannelsSection 2 Active TransportChapter 5Objectives
  • Distinguish between passive transport and active transport.
  • Explainhow the sodium-potassium pump operates.
  • Compareendocytosis and exocytosis.
  • Section 2 Active TransportChapter 5Cell Membrane Pumps
  • Active transportmoves molecules across the cell membrane from an area of lower concentration to an area of higher concentration.
  • This is going against the concentration gradient.
  • Remember that passive transport goes with the concentration gradient.
  • Unlike passive transport, active transport requires cells to expend energy.
  • Section 2 Active TransportChapter 5Cell Membrane Pumps, continued
  • Some types of active transport are performed by carrier proteins called cell membrane pumps.
  • Section 2 Active TransportChapter 5Cell Membrane Pumps, continued
  • Sodium-Potassium Pump
  • The sodium-potassium pumpmoves three Na+ ions into the cell’s external environment for every two K+ ions it moves into the cytosol.
  • ATP supplies the energy that drives the pump.
  • The conduction of nerve impulses are made possible because of the sodium-potassium pump.
  • Section 2 Active TransportChapter 5Sodium-Potassium PumpSection 2 Active TransportChapter 5Movement in Vesicles
  • Endocytosis
  • In endocytosis, cells ingest external materials by folding around them and forming a pouch.
  • The pouch then pinches off and becomes a membrane-bound organelle called a vesicle.
  • Section 2 Active TransportChapter 5Movement in Vesicles, continued
  • Endocytosis
  • Endocytosis includespinocytosis, in which the vesicle contains solutes or fluids, and phagocytosis, in which the vesicle contains large particles or cells.
  • Section 2 Active TransportChapter 5EndocytosisClick below to watch the Visual Concept.Visual ConceptSection 2 Active TransportChapter 5Movement in Vesicles, continued
  • Exocytosis
  • In exocytosis, vesicles made by the cell fuse with the cell membrane, releasing their contents into the external environment.
  • Section 2 Active TransportChapter 5ExocytosisClick below to watch the Visual Concept.Visual ConceptSection 2 Active TransportChapter 5Endocytosis and Exocytosis
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