1. Chapter 3b Transport Mechanisms

2. The next series of slides describes how various types of substances move across the plasma membrane – either into a cell…or out of a cell.

3. Passive transport (no ATP needed) Diffusion ( hi [ ] to lo [ ]) Osmosis ( hi [ ] to lo [ ]) Filtration ( hi P to lo P ) ex: kidney Carrier-mediated transport (special membrane proteins needed) facilitated transport ( hi [ ] to lo [ ]) Active Transport (ATP needed) ion pumps (ATP needed) Vesicular (“little bubble”) transport endocytosis (ex: phagocytosis, pinocytosis) exocytosis (ex: secretion of hormones) Transport Mechanisms - Overview

4. The Movement of Water - Osmosis Figure 3-7 Osmotic Flow across a Cell Membrane. (only H 2 O) Water crosses the plasma membrane thru special pores (“aquaporins”)

5. The Cell Membrane Membrane Transport Selective permeability (membrane acts like a“traffic cop.” Lets certain substances in/out as needed.) What determines permeability of a substance? Molecular size Electrical charge Shape of molecule Lipid solubility (ability to dissolve in the interior of the phospholipid bilayer.) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

6. The Cell Membrane Filtration Hydrostatic (=liquid) pressure pushes on fluid (ex. blood) Fluid crosses membrane Small solutes follow water. Large solutes (ex: proteins) stay in blood. Ex: filtration starts urine formation in the kidney Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

7. The Cell Membrane Carrier-Mediated Transport Membrane proteins act as “carriers” Facilitated diffusion (no ATP required because movement is down concentration gradient (“downhill”) Active Transport (ATP required) Molecules move against concentration gradient (“uphill”) Ion pumps (e.g., Na-K pump) (Note: ATP is the chemical in cells that provides immediate energy for all cell processes) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

8. The Cell Membrane Facilitated Diffusion Figure 3-8 Membrane Transport: Facilitated Diffusion PLAY

9. The Cell Membrane Figure 3-9 PLAY Membrane Transport: Active Transport The Sodium- Potassium Exchange Pump uses ATP energy moves ions from lower to higher [ ]

10. The Cell Membrane Vesicular (“little bubble”) Transport Materials enclosed in membranous vesicles Transport can be either in or out of cell Endocytosis Movement into cell pinocytosis (“cell drinking”) phagocytosis (“cell eating”) Exocytosis (think “exit”) Movement out of cell Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

11. Figure 3-11 2 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID CYTOPLASM Foreign object Cell membrane of phagocytic cell

12. Figure 3-11 3 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell membrane of phagocytic cell Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID CYTOPLASM Foreign object The pseudopodia approach one another and fuse to trap the material within the vesicle.

13. Figure 3-11 4 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell membrane of phagocytic cell Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID CYTOPLASM Foreign object Vesicle The pseudopodia approach one another and fuse to trap the material within the vesicle. The vesicle moves into the cytoplasm. Play Neutrophil Chasing Bacterium Play Ameba Capturing Small Protozoan

14. Figure 3-14 Endoplasmic reticulum Transport vesicle Golgi apparatus (a) Membrane renewal vesicles Secretory vesicles Lysosomes CYTOSOL EXTRACELLULAR FLUID Cell membrane Vesicle Incorporation in cell membrane (b)Exocytosis Secretion (ex. of exocytosis) ex: This is how hormones such as insulin and glucagon are secreted from pancreatic beta and alpha islet cells respectively. Play Endocytosis Animation Review of Endo- Exocytosis (Animation)

15. Other “Must Know” Organelles You must be able to identify the following organelles in sketch from your text nucleus, nuclear envelope, nuclear pore mitochondrion (-ia) lysosome cilia

16. The “Mighty” Mitochondrion (-ia) Key Note – “Mighty” Mitochondria Mitochondria provide nearly all the chemical energy (ATP) needed to keep your cells (and you!) alive. Mitochondria consume oxygen and organic substrates, and they generate carbon dioxide and ATP. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings