Presentation on theme: "TRANSPORT ACROSS CELL MEMBRANE-II"— Presentation transcript:
1 TRANSPORT ACROSS CELL MEMBRANE-II بسم الله الرحمن الرحيمTRANSPORT ACROSS CELL MEMBRANE-IIPrepared byDr.Mohammed Sharique Ahmed QuadriAssistant prof. PhysiologyAl Maarefa College
2 ObjectivesDescribe how energy from ATP hydrolysis is used to transport ions against their electrochemical concentration differencesExplain how energy from the Na+ and K+ electrochemical gradients across the plasma membrane can be used to drive the net “uphill” (against a gradient) movement of other solutes.Describe the characteristics of carrier-mediated transport, and distinguish between simple diffusion, facilitated diffusion, and active transportDescribe the process of vesicular transport
3 Active Transport Active transport Moves a substance against its concentration gradientRequires a carrier moleculeRequires energy
4 Types of Active Transport Protein PumpsPrimary active transportRequires direct use of ATPSecondary active transportDriven by an ion concentration gradient established by a primary active transport systemVesicular transportEndocytosisExocytosis
5 Primary Active Transport Movement against concentration gradientHydrolysis of ATP directly required for the function of the carriers.Molecule or ion binds to “recognition site” on one side of carrier protein.Carrier protein undergoes conformational change.Hinge-like motion releases transported molecules to opposite side of membrane.
7 Na+/K+ Pump Carrier protein has enzymes activity ( ATPase) Extrudes 3 Na+ and transports 2 K+ inward against concentration gradient.
8 Na+/K+ PumpSteep gradient created by this pump serves following functions:Provides energy for “coupled transport” of other molecules.Involvement in electrochemical impulses.Promotes osmotic flow.
9 Importance of Na+- K+ pump in intestinal epithelium High osmotic pressure created by movement of sodium causes water to move from intestinal lumen to interstitial spaceProtein and glucose r transported actively by cotransport with sodiumChloride passively follow the electrical gradient created by sodium
10 Secondary Active Transport Transport of two or more solutes are Coupled .Energy needed for “uphill” movement obtained from “downhill” transport of Na+.Hydrolysis of ATP by Na+/K+ pump required indirectly to maintain [Na+] gradient.
11 Secondary Active Transport Cotransport (symport):Molecule or ion moving in the same direction as Na+.Countertransport (antiport):Molecule or ion moving in the opposite direction of Na+.
14 Counter transport Molecule or ion moving in the opposite direction E.g. Na+-Ca2+ exchangeAs with cotransport it also uses Na gradient established by the Na+- K+ ATPase as an energy sourceNa+ moves downhill & Ca2+ moves uphill
15 Vesicular transport across membrane ExocytoseEndocytosis
16 Types of Active Transport Endocytosis: taking bulky material into a cellUses energyCell membrane in-folds around food particle“cell eating”forms food vacuole & digests foodThis is how white blood cells eat bacteria!
17 Types of Active Transport 3. Exocytosis: Forces material out of cell in bulkmembrane surrounding the material fuses with cell membraneCell changes shape – requires energyEX: Hormones or wastes released from cell
18 Vesicle-mediated transport Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the cell.