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Chapter 5b

Chapter 5b. Membrane Dynamics. Energy Transfer in Living Cells. Glucose. Energy is imported into the cell as energy stored in chemical bonds of nutrients such as glucose. Glucose. Glycolysis. ATP. Pyruvate. Metabolism. The chemical bond energy is converted

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Chapter 5b

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  1. Chapter 5b Membrane Dynamics

  2. Energy Transfer in Living Cells Glucose Energy is imported into the cell as energy stored in chemical bonds of nutrients such as glucose. Glucose Glycolysis ATP Pyruvate Metabolism The chemical bond energy is converted into high-energy bonds of ATP through the process of metabolism. Heat CA cycle H2O ETS CO2 Primary active transport Na+ The energy in the high-energy phosphate bond of ATP is used to move K+ and Na+ against their concentration gradients. This creates potential energy stored in the ion concentration gradients. ATP K+ ATP O2 ADP+Pi High [K+] Low [K+] Low [Na+] High [Na+] Secondary active transport Na+ K+ The energy of the Na+ gradient can be used to move other molecules across the cell membrane against their concentration gradients. 2 Cl– KEY CA cycle ETS = Citric acid cycle = Electron transport system Figure 5-16

  3. Carrier-Mediated Transport • Specificity • Competition • Saturation • Transport maximum

  4. Carrier-Mediated Transport Competition Figure 5-17

  5. Carrier-Mediated Transport Competition Extracellular fluid Glucose Glucose Maltose GLUT transporter Intracellular fluid (b) Maltose (a) The GLUT transporter Figure 5-18

  6. Carrier-Mediated Transport Saturation Figure 5-19

  7. Vesicular Transport • Phagocytosis • Cell engulfs bacterium or other particle into phagosome • Endocytosis • Membrane surface indents and forms vesicles • Active process that can be nonselective (pinocytosis) or highly selective • Potocytosisuses caveolae • Receptor-mediated uses clathrin-coated pits

  8. Phagocytosis Bacterium 3 The phagosome containing the bacterium separates from the cell membrane and moves into the cytoplasm. Phagocyte Lysosome 4 The phagosome fuses with lysosomes containing digestive enzymes. 1 The phagocytic white blood cell encounters a bacterium that binds to the cell membrane. 5 The bacterium is killed and digested within the vesicle. 2 The phagocyte uses its cytoskeleton to push its cell membrane around the bacterium, creating a large vesicle, the phagosome. Figure 5-20

  9. Phagocytosis Bacterium Phagocyte Lysosome 1 The phagocytic white blood cell encounters a bacterium that binds to the cell membrane. Figure 5-20, step 1

  10. Phagocytosis Bacterium Phagocyte Lysosome 1 The phagocytic white blood cell encounters a bacterium that binds to the cell membrane. 2 The phagocyte uses its cytoskeleton to push its cell membrane around the bacterium, creating a large vesicle, the phagosome. Figure 5-20, steps 1–2

  11. Phagocytosis Bacterium 3 The phagosome containing the bacterium separates from the cell membrane and moves into the cytoplasm. Phagocyte Lysosome 1 The phagocytic white blood cell encounters a bacterium that binds to the cell membrane. 2 The phagocyte uses its cytoskeleton to push its cell membrane around the bacterium, creating a large vesicle, the phagosome. Figure 5-20, steps 1–3

  12. Phagocytosis Bacterium 3 The phagosome containing the bacterium separates from the cell membrane and moves into the cytoplasm. Phagocyte Lysosome 4 The phagosome fuses with lysosomes containing digestive enzymes. 1 The phagocytic white blood cell encounters a bacterium that binds to the cell membrane. 2 The phagocyte uses its cytoskeleton to push its cell membrane around the bacterium, creating a large vesicle, the phagosome. Figure 5-20, steps 1–4

  13. Phagocytosis Bacterium 3 The phagosome containing the bacterium separates from the cell membrane and moves into the cytoplasm. Phagocyte Lysosome 4 The phagosome fuses with lysosomes containing digestive enzymes. 1 The phagocytic white blood cell encounters a bacterium that binds to the cell membrane. 5 The bacterium is killed and digested within the vesicle. 2 The phagocyte uses its cytoskeleton to push its cell membrane around the bacterium, creating a large vesicle, the phagosome. Figure 5-20, steps 1–5

  14. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 9 Exocytosis 2 Receptor-ligand migrates to clathrin-coated pit. 8 Transport vesicle and cell membrane fuse (membrane recycling). Clathrin-coated pit 3 Endocytosis Receptor Clathrin 4 Vesicle loses clathrin coat. 7 Transport vesicle with receptors moves to the cell membrane. 5 Receptors and ligands separate. To lysosome or Golgi complex Intracellular fluid 6 Endosome Ligands go to lysosomes or Golgi for processing. Figure 5-21

  15. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid Receptor Intracellular fluid Figure 5-21, step 1

  16. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 2 Receptor-ligand migrates to clathrin-coated pit. Clathrin-coated pit Receptor Clathrin Intracellular fluid Figure 5-21, steps 1–2

  17. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 2 Receptor-ligand migrates to clathrin-coated pit. Clathrin-coated pit 3 Endocytosis Receptor Clathrin Intracellular fluid Figure 5-21, steps 1–3

  18. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 2 Receptor-ligand migrates to clathrin-coated pit. Clathrin-coated pit 3 Endocytosis Receptor Clathrin 4 Vesicle loses clathrin coat. Intracellular fluid Figure 5-21, steps 1–4

  19. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 2 Receptor-ligand migrates to clathrin-coated pit. Clathrin-coated pit 3 Endocytosis Receptor Clathrin 4 Vesicle loses clathrin coat. 5 Receptors and ligands separate. Intracellular fluid Endosome Figure 5-21, steps 1–5

  20. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 2 Receptor-ligand migrates to clathrin-coated pit. Clathrin-coated pit 3 Endocytosis Receptor Clathrin 4 Vesicle loses clathrin coat. 5 Receptors and ligands separate. To lysosome or Golgi complex Intracellular fluid 6 Endosome Ligands go to lysosomes or Golgi for processing. Figure 5-21, steps 1–6

  21. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 2 Receptor-ligand migrates to clathrin-coated pit. Clathrin-coated pit 3 Endocytosis Receptor Clathrin 4 Vesicle loses clathrin coat. 7 Transport vesicle with receptors moves to the cell membrane. 5 Receptors and ligands separate. To lysosome or Golgi complex Intracellular fluid 6 Endosome Ligands go to lysosomes or Golgi for processing. Figure 5-21, steps 1–7

  22. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 2 Receptor-ligand migrates to clathrin-coated pit. 8 Transport vesicle and cell membrane fuse (membrane recycling). Clathrin-coated pit 3 Endocytosis Receptor Clathrin 4 Vesicle loses clathrin coat. 7 Transport vesicle with receptors moves to the cell membrane. 5 Receptors and ligands separate. To lysosome or Golgi complex Intracellular fluid 6 Endosome Ligands go to lysosomes or Golgi for processing. Figure 5-21, steps 1–8

  23. Receptor-Mediated Endocytosis and Exocytosis 1 Ligand binds to membrane receptor. Extracellular fluid 9 Exocytosis 2 Receptor-ligand migrates to clathrin-coated pit. 8 Transport vesicle and cell membrane fuse (membrane recycling). Clathrin-coated pit 3 Endocytosis Receptor Clathrin 4 Vesicle loses clathrin coat. 7 Transport vesicle with receptors moves to the cell membrane. 5 Receptors and ligands separate. To lysosome or Golgi complex Intracellular fluid 6 Endosome Ligands go to lysosomes or Golgi for processing. Figure 5-21, steps 1–9

  24. Transepithelial Transport • Polarized cells of transporting epithelia Lumen of intestine or kidney Apical membrane Tight junction Transporting epithelial cell Basolateral membrane Extracellular fluid Transport proteins Figure 5-22

  25. Transepithelial Transport of Glucose [Glucose] low [Na+] high Lumen of kidney or intestine 1 Na+-glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient. 1 Apical membrane 2 GLUT transporter transfers glucose to ECF by facilitated diffusion. [Glucose] high [Na+] low 3 Na+-K+- ATPase pumps Na+ out of the cell, keeping ICF Na+ concentration low. Epithelial cell Basolateral membrane 2 3 Extracellular fluid [Glucose] low [Na+] high Figure 5-23

  26. Transepithelial Transport of Glucose [Glucose] low [Na+] high Lumen of kidney or intestine 1 Na+-glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient. 1 Apical membrane [Glucose] high [Na+] low Epithelial cell Basolateral membrane Extracellular fluid Figure 5-23, step 1

  27. Transepithelial Transport of Glucose [Glucose] low [Na+] high Lumen of kidney or intestine 1 Na+-glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient. 1 Apical membrane 2 GLUT transporter transfers glucose to ECF by facilitated diffusion. [Glucose] high [Na+] low Epithelial cell Basolateral membrane 2 Extracellular fluid [Glucose] low Figure 5-23, steps 1–2

  28. Transepithelial Transport of Glucose [Glucose] low [Na+] high Lumen of kidney or intestine 1 Na+-glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient. 1 Apical membrane 2 GLUT transporter transfers glucose to ECF by facilitated diffusion. [Glucose] high [Na+] low 3 Na+-K+- ATPase pumps Na+ out of the cell, keeping ICF Na+ concentration low. Epithelial cell Basolateral membrane 2 3 Extracellular fluid [Glucose] low [Na+] high Figure 5-23, steps 1–3

  29. Transcytosis Across the Capillary Endothelium Red blood cell Plasma proteins 1 Plasma proteins are concentrated in caveolae, which then undergo endocytosis and form vesicles. Caveolae Endocytosis 1 Capillary endothelium 2 2 Vesicles cross the cell with help from the cytoskeleton. Vesicular transport 3 3 Vesicle contents are released into interstitial fluid by exocytosis. Exocytosis Interstitial fluid Figure 5-24

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