Membrane Structure and Function Chapter 7 Membrane Structure and Function

Phospholipid bilayer Hydrophobic regions of protein Hydrophilic Fig. 7-3 What component of the cell membrane deals with the fluid part of the model? The mosaic part? Phospholipid bilayer Figure 7.3 The fluid mosaic model for membranes Hydrophobic regions of protein Hydrophilic regions of protein

Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails Fig. 7-5b How else can animal cells adjust the fluidity of the cell membrane? Fluid Viscous Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails Figure 7.5b The fluidity of membranes (b) Membrane fluidity

Membrane proteins Mixed proteins after 1 hour Mouse cell Human cell Fig. 7-6 If, after many hours, the protein distribution still looked like that in the third image above, would you be able to conclude that proteins don’t move within the membrane? What other explanation could there be? RESULTS Membrane proteins Mixed proteins after 1 hour Mouse cell Figure 7.6 Do membrane proteins move? Human cell Hybrid cell

EXTRACELLULAR N-terminus SIDE C-terminus CYTOPLASMIC SIDE  Helix Fig. 7-8 Why is this called a transmembrane protein? EXTRACELLULAR SIDE N-terminus Figure 7.8 The structure of a transmembrane protein C-terminus CYTOPLASMIC SIDE  Helix

(b) Enzymatic activity (c) Signal transduction Fig. 7-9 Some transmembrane proteins can bind to a particular ECM molecule and, when bound, transmit a signal into the cell. Use the proteins shown here to explain how this might occur. Signaling molecule Enzymes Receptor ATP Signal transduction (a) Transport (b) Enzymatic activity (c) Signal transduction Figure 7.9 Some functions of membrane proteins Glyco- protein (d) Cell-cell recognition (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM)

ER Transmembrane glycoproteins Secretory protein Glycolipid Golgi Fig. 7-10 Number the order of the protein pathway. ER Transmembrane glycoproteins Secretory protein Glycolipid Golgi apparatus Vesicle Figure 7.10 Synthesis of membrane components and their orientation on the resulting membrane Plasma membrane: Cytoplasmic face Extracellular face Transmembrane glycoprotein Secreted protein Membrane glycolipid

Animation: Membrane Selectivity Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment Animation: Membrane Selectivity Animation: Diffusion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Membrane (cross section) Fig. 7-11a Is the movement of the dye random? Explain your answer. Molecules of dye Membrane (cross section) WATER Figure 7.11a The diffusion of solutes across a membrane Net diffusion Net diffusion Equilibrium (a) Diffusion of one solute

(b) Diffusion of two solutes Fig. 7-11b True or False. Once a dye molecule moves to one side, it is impossible for it to move back to the original side it was on. Net diffusion Net diffusion Equilibrium Figure 7.11b The diffusion of solutes across a membrane Net diffusion Net diffusion Equilibrium (b) Diffusion of two solutes

Higher concentration Lower Same concentration concentration of sugar Fig. 7-12 If an orange dye capable of passing through the membrane was added to the left side of the tube above, how would it be distributed at the end of the process? Would the solution levels in the tube on the right be affected? Lower concentration of solute (sugar) Higher concentration of sugar Same concentration of sugar H2O Selectively permeable membrane Figure 7.12 Osmosis Osmosis

cell cell _________ solution _______ solution _________ solution H2O Fig. 7-13 Fill in the missing information. _________ solution _______ solution _________ solution H2O H2O H2O H2O (a)_______ cell ________________ Normal ___________________ H2O H2O H2O H2O Figure 7.13 The water balance of living cells (b) Plant cell _____________ ___________ _____________

(a) A contractile vacuole fills with fluid that enters from Fig. 7-14 How does the paramecium counteract osmosis? 50 µm Filling vacuole (a) A contractile vacuole fills with fluid that enters from a system of canals radiating throughout the cytoplasm. Contracting vacuole Figure 7.14 The contractile vacuole of Paramecium: an evolutionary adaptation for osmoregulation (b) When full, the vacuole and canals contract, expelling fluid from the cell.

Video: Plasmolysis Video: Turgid Elodea Animation: Osmosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Channel protein Solute (a) A channel protein Solute Carrier protein Fig. 7-15 Which protein deals with changing shape? EXTRACELLULAR FLUID Channel protein Solute CYTOPLASM (a) A channel protein Figure 7.15 Two types of transport proteins that carry out facilitated diffusion Solute Carrier protein (b) A carrier protein

The Need for Energy in Active Transport Animation: Active Transport Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

1 2 3 6 5 4 EXTRACELLULAR FLUID [Na+] high Na+ [K+] low Na+ Na+ Na+ Fig. 7-16-7 Summarize each of the 6 steps. EXTRACELLULAR FLUID [Na+] high Na+ [K+] low Na+ Na+ Na+ Na+ Na+ Na+ Na+ [Na+] low ATP P Na+ P CYTOPLASM [K+] high ADP 1 2 3 K+ Figure 7.16, 1–6 The sodium-potassium pump: a specific case of active transport K+ K+ K+ K+ P K+ P 6 5 4

Facilitated diffusion Fig. 7-17 How is passive transport similar to active transport? How are they different? Active transport Passive transport ATP Diffusion Facilitated diffusion Figure 7.17 Review: passive and active transport

– + H+ ATP H+ – + H+ H+ – + H+ H+ – + H+ H+ – + – + Diffusion of H+ Fig. 7-19 How does the cell produce and then maintain the proton gradient? – + H+ ATP H+ – + Proton pump H+ H+ – + H+ H+ – + H+ Diffusion of H+ Sucrose-H+ cotransporter Figure 7.19 Cotransport: active transport driven by a concentration gradient H+ – Sucrose + – + Sucrose

Animation: Exocytosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Animation: Exocytosis and Endocytosis Introduction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Animation: Phagocytosis For the Cell Biology Video Phagocytosis in Action, go to Animation and Video Files. Animation: Phagocytosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PHAGOCYTOSIS CYTOPLASM 1 µm EXTRACELLULAR FLUID Pseudopodium Fig. 7-20a How is the extracellular particle digested once inside the cell? PHAGOCYTOSIS EXTRACELLULAR FLUID CYTOPLASM 1 µm Pseudopodium Pseudopodium of amoeba “Food” or other particle Bacterium Food vacuole Figure 7.20 Endocytosis in animal cells—phagocytosis Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM)

Animation: Pinocytosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PINOCYTOSIS Plasma membrane Vesicle 0.5 µm Fig. 7-20b How is pinocytosis different from phagocytosis? PINOCYTOSIS 0.5 µm Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM) Vesicle Figure 7.20 Endocytosis in animal cells—pinocytosis

Animation: Receptor-Mediated Endocytosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit Fig. 7-20c How is receptor mediated endocytosis different from pinocytosis? RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit and a coated vesicle formed during receptor- mediated endocytosis (TEMs) Coat protein Figure 7.20 Endocytosis in animal cells—receptor-mediated endocytosis Plasma membrane 0.25 µm