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Chapter 11. Membranes: Transport Part 2. Learning Goals. To KNOW: mechanisms of molecular transport in and out of cells. transport kinetics (really easy after Chapter 6!)

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Chapter 11


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    1. Chapter 11 Membranes: Transport Part 2

    2. Learning Goals • To KNOW: • mechanisms of molecular transport in and out of cells. • transport kinetics (really easy after Chapter 6!) • specific transporters: Ca++ transporter, Na+/K+ transporter, glucose transport in gut epithelial cells, P,V and F-type ATPases, lactose transport in bacteria • aquaporins

    3. Membrane Transport

    4. Energetics of Diffusion Transport EOC Problem 15 is all about tryptophan and indole permeability, review their structure (Chapter 3) or you already know it !!

    5. Glut1 Transporter (Erythrocyte Glucose Transporter)

    6. Each α-helix has a Non Polar Side and Polar Side

    7. Polar Groups Define the Transporter Pore EOC Problem 11 deals with evidence on the location of membrane proteins. A good class activity.

    8. Transport Kinetics vo = Vmax [Sout] / (Kt + [Sout]) ktis the same as kcat…. and Ktis Km of transport

    9. Glucose Transport Model

    10. Tissues where Expressed Kt (mM) Role

    11. Insulin Increases Number of Glucose Transporters Related to this is membrane self-sealing: Check out EOC Problem 12

    12. Chloride Transporter Linked to CO2 Exchange

    13. Secondary Transporters Secondary Transporters = use a chemical gradient + electrical gradient.

    14. Two Types of Active Transport

    15. S1 is usually H+ or Na+ Therefore Outside Cell Membrane (Na+) or Mitochondria Membrane (H+) there is: high concentration of S1and lower in the cytoplasm or mitochondrial matrix. On the outside: higher chemical conc. + electrical charge …….these are 2 energetic components. This is called either the Proton Motive Force or Sodium Motive Force

    16. EOC Problem 10: Energetics of symports.

    17. Ca++ Transporter in Sarcoplasmic Reticulum

    18. Ca++ Transporter works like a little motor

    19. General Structure P-type ATPases

    20. P-type Na+K+ ATPase

    21. Inhibitor of P-type ATPases which become Phosphorylated in the Transport Cycle

    22. P-type Na+/K+ ATPase Maintains the Na+ - K+ disequilibrium If you add up just the sodium and potassium concentrations…it doesn’t seem right, but it is because the concentrations of Cl-, Mg++, Ca++ and all the other weak acids are all part of the overall electrochemical-gradient.

    23. Ouabain Binds to the Open - Outside form of Na+K+ATPase..and hold it there. Arrow Poison

    24. V-type and F-type ATPase

    25. F-type ATPase Is Reversible and Can Make ATP

    26. ABC Transporters in E. coli Nucleotide Binding Domains Lipid-a Flippase Vit-B12 Transporter

    27. CFTR (Chloride Transporter) Cystic Fibrosis Transmembrane conductance Regulator

    28. Cystic Fibrosis Patients Can’t Clear Bacteria in Bronchia-Trachea Cystic Fibrosis – Research at FIU in Dr. Kalai Mathee’s Lab

    29. CFTR In Action See Box 11-2 Page 415 For More

    30. Proton Motive Force

    31. Lactose Transporter in Two Forms 12 Transmembrane Helices Arg and Glu in Green, Lactose in Red

    32. Transporters Need to be at the Right Side of a Cell

    33. How Are Transporters Regulated? 1st Crystal Structure of the E. coli Methionine ABC Transporter Fig. 1. (A) ABC transporter MetNI consists of four subunits: two membrane-spanning MetI subunits (green and pink) and two MetN ABC subunits (purple and tan) Structure B is A in a 90o Turn TMD – transmembrane domain, NBD – Nucleotide binding domain, C-2 Methionine binding domain

    34. C-2 Domain of Met-Transporter Methoinine – gold structures. When bound, Met inhibits the NDB as an ATPase, Ki ~ 30 µM Ref: Kadaba, Kaiser, Johnson, Lee and Rees. 2008. The high affinity E. coli methionine ABC transporter: structure and allosteric regulation. SCIENCE 231:250-253

    35. Ionophores (Valinomycin) Disrupt Ion Gradients K+

    36. Discovered Aquaporins (AQP) – Water Transport

    37. Aquaporins

    38. EOC Problem 16 is a classic aquaporin water flow kinetics problem.

    39. Things to Know Membrane transport kinetics: KT and kt Amino acids in transmembrane domain of transporters. Primary and Secondary Transporters. Transporters as motors. PMF. Cell location of transporters: intestinal cell model. Transporter regulation Aquaporins EOC Problems : 10-13, 15, 16, 22 .

    40. Model for EOC Problem 22 Fill in the Amino Acids with Single Letter Code: What does it tell you? Val-Asp-Arg-Val-Phe-Ser-Asn-Val-Cys-Thr-His-Leu-Lys-Thr-Leu-Gln-Asp-Lys