3Membrane Transport: Active ProcessesActive TransportPrimary Active TransportSlide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Secondary Active TransportSlide 15Slide 16Slide 17Slide 18Vesicular TransportSlide 20Endocytosis and TranscytosisSlide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28EndocytosisSlide 30Slide 31Slide 32Slide 33Slide 34ExocytosisSlide 36Summary of Active ProcessesCells: The Living Units: Part BTwo types of active processes:◦Active transport◦Vesicular transportBoth use ATP to move solutes across a living plasma membraneRequires carrier proteins (solute pumps)Moves solutes against a concentration gradientTypes of active transport:◦Primary active transport◦Secondary active transportEnergy from hydrolysis of ATP causes shape change in transport protein so that bound solutes (ions) are “pumped” across the membraneSodium-potassium pump (Na+-K+ ATPase)◦Located in all plasma membranes◦Involved in primary and secondary active transport of nutrients and ions◦Maintains electrochemical gradients essential for functions of muscle and nerve tissuesCopyright © 2010 Pearson Education, Inc.Figure 3.10Extracellular fluid K+ is released from the pump proteinand Na+ sites are ready to bind Na+ again.The cycle repeats. Binding of Na+ promotesphosphorylation of the protein by ATP.Cytoplasmic Na+ binds to pump protein.Na+Na+-K+ pumpK+ releasedATP-binding siteNa+ boundCytoplasmATPADPPK+ K+ binding triggers release of thephosphate. Pump protein returns to itsoriginal conformation. Phosphorylation causes the protein tochange shape, expelling Na+ to the outside.Extracellular K+ binds to pump protein.Na+ releasedK+ boundPK+PPi123456Copyright © 2010 Pearson Education, Inc.Figure 3.10 step 1Extracellular fluidCytoplasmic Na+ binds to pump protein.Na+Na+-K+ pumpATP-binding siteCytoplasmK+1Copyright © 2010 Pearson Education, Inc.Figure 3.10 step 2 Binding of Na+ promotesphosphorylation of the protein by ATP.Na+ boundATPADPP2Copyright © 2010 Pearson Education, Inc.Figure 3.10 step 3 Phosphorylation causes the protein tochange shape, expelling Na+ to the outside.Na+ releasedP3Copyright © 2010 Pearson Education, Inc.Figure 3.10 step 4Extracellular K+ binds to pump protein.PK+4Copyright © 2010 Pearson Education, Inc.Figure 3.10 step 5 K+ binding triggers release of thephosphate. Pump protein returns to itsoriginal conformation.K+ boundPi5Copyright © 2010 Pearson Education, Inc.Figure 3.10 step 6 K+ is released from the pump proteinand Na+ sites are ready to bind Na+ again.The cycle repeats.K+ released6Copyright © 2010 Pearson Education, Inc.Figure 3.10Extracellular fluid K+ is released from the pump proteinand Na+ sites are ready to bind Na+ again.The cycle repeats. Binding of Na+ promotesphosphorylation of the protein by ATP.Cytoplasmic Na+ binds to pump protein.Na+Na+-K+ pumpK+ releasedATP-binding siteNa+ boundCytoplasmATPADPPK+ K+ binding triggers release of thephosphate. Pump protein returns to itsoriginal conformation. Phosphorylation causes the protein tochange shape, expelling Na+ to the outside.Extracellular K+ binds to pump protein.Na+ releasedK+ boundPK+PPi123456Depends on an ion gradient created by primary active transportEnergy stored in ionic gradients is used indirectly to drive transport of other solutesCotransport—always transports more than one substance at a time◦Symport system: Two substances transported in same direction◦Antiport system: Two substances transported in opposite directionsCopyright © 2010 Pearson Education, Inc.Figure 3.11 The ATP-driven Na+-K+ pump stores energy by creating a steep concentration gradient for Na+ entry into the cell. As Na+ diffuses back across the membrane through a membrane cotransporter protein, it drives glucose against its concentration gradientinto the cell. (ECF = extracellular fluid)Na+-glucosesymporttransporterloadingglucose fromECFNa+-glucosesymport transporterreleasing glucoseinto the cytoplasmGlucoseNa+-K+pumpCytoplasmExtracellular fluid1 2Copyright © 2010 Pearson Education, Inc.Figure 3.11 step 1 The ATP-driven Na+-K+ pump stores energy by creating a steep concentration gradient for Na+ entry into the cell.Na+-K+pumpCytoplasmExtracellular fluid1Copyright © 2010 Pearson Education, Inc.Figure 3.11 step 2 The ATP-driven Na+-K+ pump stores energy by creating a steep concentration gradient for Na+ entry into the cell. As Na+ diffuses back across the membrane through a membrane cotransporter protein, it drives glucose against its concentration gradientinto the cell. (ECF = extracellular fluid)Na+-glucosesymporttransporterloadingglucose fromECFNa+-glucosesymport transporterreleasing glucoseinto the cytoplasmGlucoseNa+-K+pumpCytoplasmExtracellular fluid1 2Transport of large particles, macromolecules, and fluids across plasma membranesRequires cellular energy (e.g., ATP)Functions:◦Exocytosis — transport out of cell ◦Endocytosis — transport into cell◦Transcytosis — transport into, across, and then out of cell◦Substance (vesicular) trafficking—transport from one area or organelle in cell to anotherInvolve formation of protein-coated vesiclesOften receptor mediated, therefore very selectiveCopyright © 2010 Pearson Education, Inc.Figure 3.12 Coated pit ingestssubstance.Protein-coatedvesicledetaches. Coat proteins detachand are recycled toplasma membrane. Uncoated vesicle fuseswith a sorting vesiclecalled an endosome. Transportvesicle containingmembrane componentsmoves to the plasmamembrane for recycling.Fused vesicle may (a) fusewith lysosome for digestionof its contents, or (b) deliverits contents to the plasmamembrane on theopposite side of the cell(transcytosis).Protein coat(typicallyclathrin)Extracellular fluidPlasmamembraneEndosomeLysosomeTransportvesicle(b)(a)Uncoatedendocytic vesicleCytoplasm123456Copyright © 2010 Pearson Education, Inc.Figure 3.12 step 1 Coated pit ingestssubstance.Protein coat(typicallyclathrin)Extracellular fluidPlasmamembraneCytoplasm1Copyright © 2010 Pearson Education, Inc.Figure 3.12 step 2 Coated pit ingestssubstance.Protein-coatedvesicledetaches.Protein coat(typicallyclathrin)Extracellular fluidPlasmamembraneCytoplasm12Copyright © 2010 Pearson Education, Inc.Figure 3.12 step 3 Coated pit ingestssubstance.Protein-coatedvesicledetaches. Coat proteins detachand are recycled toplasma