Membrane Dynamics 5

Carrier-Mediated Transport Specificity Competition Saturation Transport maximum

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

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid To lysosome or Golgi complex Receptor-ligand migrates to clathrin-coated pit. Endocytosis Vesicle loses clathrin coat. Ligands go to lysosomes or Golgi for processing. Transport vesicle with receptors moves to the cell membrane. and cell membrane fuse (membrane recycling). Exocytosis Clathrin Endosome Receptors and ligands separate. Receptor 4 1 2 3 9 8 7 6 5 Figure 5-24

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Extracellular fluid Intracellular fluid Receptor 1 Figure 5-24, step 1

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid Receptor-ligand migrates to clathrin-coated pit. Clathrin Receptor 1 2 Figure 5-24, steps 1–2

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid Receptor-ligand migrates to clathrin-coated pit. Endocytosis Clathrin Receptor 1 2 3 Figure 5-24, steps 1–3

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid Receptor-ligand migrates to clathrin-coated pit. Endocytosis Vesicle loses clathrin coat. Clathrin Receptor 4 1 2 3 Figure 5-24, steps 1–4

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid Receptor-ligand migrates to clathrin-coated pit. Endocytosis Vesicle loses clathrin coat. Clathrin Endosome Receptors and ligands separate. Receptor 4 1 2 3 5 Figure 5-24, steps 1–5

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid To lysosome or Golgi complex Receptor-ligand migrates to clathrin-coated pit. Endocytosis Vesicle loses clathrin coat. Ligands go to lysosomes or Golgi for processing. Clathrin Endosome Receptors and ligands separate. Receptor 4 1 2 3 6 5 Figure 5-24, steps 1–6

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid To lysosome or Golgi complex Receptor-ligand migrates to clathrin-coated pit. Endocytosis Vesicle loses clathrin coat. Ligands go to lysosomes or Golgi for processing. Transport vesicle with receptors moves to the cell membrane. Clathrin Endosome Receptors and ligands separate. Receptor 4 1 2 3 7 6 5 Figure 5-24, steps 1–7

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid To lysosome or Golgi complex Receptor-ligand migrates to clathrin-coated pit. Endocytosis Vesicle loses clathrin coat. Ligands go to lysosomes or Golgi for processing. Transport vesicle with receptors moves to the cell membrane. and cell membrane fuse (membrane recycling). Clathrin Endosome Receptors and ligands separate. Receptor 4 1 2 3 8 7 6 5 Figure 5-24, steps 1–8

Receptor-Mediated Endocytosis and Exocytosis Ligand binds to membrane receptor. Clathrin- coated pit Extracellular fluid Intracellular fluid To lysosome or Golgi complex Receptor-ligand migrates to clathrin-coated pit. Endocytosis Vesicle loses clathrin coat. Ligands go to lysosomes or Golgi for processing. Transport vesicle with receptors moves to the cell membrane. and cell membrane fuse (membrane recycling). Exocytosis Clathrin Endosome Receptors and ligands separate. Receptor 4 1 2 3 9 8 7 6 5 Exocytosis is the opposite of endocytosis Figure 5-24, steps 1–9

Transepithelial Transport Polarized cells of transporting epithelia Figure 5-25

Transepithelial Transport of Glucose [Glucose] low [Glucose] high [Na+] high Na+ Apical membrane Glu Na+ [Na+] high Na+ [Na+] low Na+ K+ Basolateral Extracellular fluid Lumen of kidney or intestine GLUT transporter transfers glucose to ECF by facilitated diffusion. Na+ -K+- ATPase pumps Na+ out of the cell, keeping ICF Na+ concentration low. Na+ glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient. ATP Epithelial cell 1 2 3 Figure 5-26

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

Transepithelial Transport of Glucose [Glucose] low [Glucose] high Apical membrane Glu Na+ [Na+] high Na+ [Na+] low Basolateral Extracellular fluid Lumen of kidney or intestine GLUT transporter transfers glucose to ECF by facilitated diffusion. Na+ glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient. Epithelial cell 1 2 Figure 5-26, steps 1–2

Transepithelial Transport of Glucose [Glucose] low [Glucose] high [Na+] high Na+ Apical membrane Glu Na+ [Na+] high Na+ [Na+] low Na+ K+ Basolateral Extracellular fluid Lumen of kidney or intestine GLUT transporter transfers glucose to ECF by facilitated diffusion. Na+ -K+- ATPase pumps Na+ out of the cell, keeping ICF Na+ concentration low. Na+ glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient. ATP Epithelial cell 1 2 3 Figure 5-26, steps 1–3

Transcytosis across the Capillary Endothelium Figure 5-27

Transcytosis across the Capillary Endothelium Figure 5-27 (1 of 3)

Transcytosis across the Capillary Endothelium Figure 5-27 (2 of 3)

Transcytosis across the Capillary Endothelium Figure 5-27 (3 of 3)

Transcytosis across the Capillary Endothelium Figure 5-27