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Facilitated Diffusion

Facilitated Diffusion. “Downhill” movement e.g., glucose e.g., amino acids carrier protein similarities to enzyme function binding is specific process can be saturated There is a maximum transport rate (cf. v max ). . Fig. 3.18. Facilitated Diffusion of Glucose. Fig. 19.5 Ganong

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Facilitated Diffusion

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  1. FacilitatedDiffusion • “Downhill” movement • e.g., glucose • e.g., amino acids • carrier protein • similarities to enzyme function • binding is specific • process can be saturated There is a maximum transport rate (cf. vmax). Fig. 3.18

  2. Facilitated Diffusion of Glucose Fig. 19.5 Ganong See Table 19-5 Ganong. For example: Glut 4 transporter glucose transport into skeletal muscle and fat cells Glut 2 transporter glucose transport out of intestinal and renal cells

  3. Active Transport • “Uphill” movement • movement of a substance against its electrochemical gradient • therefore, REQUIRES ENERGY • Primary Active Transport • Secondary Active Transport

  4. Primary Active Transport ATP used directly in the process Fig. 3.19 “high” [Na+] “high” [K+] - 70 mv (for a neuron) The sodium pump = Na+-K+ ATPase = Na+-K+ pump All animal cells must have a sodium pump to prevent cell swelling. K+ chemical gradient: uphill electrical gradient: downhill electrochemical gradient: ? Na+ chemical gradient: uphill electrical gradient: uphill electrochemical gradient: uphill

  5. Secondary Active Transport no direct use of ATP Concentration gradients provide energy. ATP requirement is indirect. • Symport (“piggy-back,” same direction) • SGLT: sodium-dependent glucose transporters • into intestinal and renal cells • sodium-dependent amino acid transporters • into intestinal and renal cells • Antiport (“see-saw,” opposite directions) • Na+-Ca2+ exchanger • cardiac muscle • Na+-H+ exchanger • renal tubular cells Fig. 3.20

  6. Major Transporters of the Proximal Convoluted Tubule of the Kidneys Fig. 23.15

  7. Vesicular Transport Exo- and Endocytosis Topologically speaking, the inside of the inside is equivalent to the outside. Fig. 3.24 e.g., secretion e.g., phagocytosis, pinocytosis, receptor-mediated endocytosis Fig. 1-25 G

  8. More Detailed Views Fig. 3.22 Exocytosis Figs. 4-4 & 4-5 G receptor-mediated endocytosis release (exocytosis) of neurotransmitter from axon terminal

  9. Phagocytosis: Cell Eating Fig. 3.21

  10. Pinocytosis: Cell Drinking Fig. 3.23

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