Fig. 7-1 Figure 7.1 How do cell membrane proteins help regulate chemical traffic?

WATER Hydrophilic head Hydrophobic tail WATER Fig. 7-2 Figure 7.2 Phospholipid bilayer (cross section) Hydrophobic tail WATER

Phospholipid bilayer Hydrophobic regions of protein Hydrophilic Fig. 7-3 Phospholipid bilayer Figure 7.3 The fluid mosaic model for membranes Hydrophobic regions of protein Hydrophilic regions of protein

Inside of extracellular layer Knife Fig. 7-4 TECHNIQUE RESULTS Extracellular layer Proteins Inside of extracellular layer Knife Figure 7.4 Freeze-fracture Plasma membrane Cytoplasmic layer Inside of cytoplasmic layer

Fig. 7-5 Lateral movement (~107 times per second) Flip-flop (~ once per month) (a) Movement of phospholipids Fluid Viscous Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails (b) Membrane fluidity Figure 7.5 The fluidity of membranes Cholesterol (c) Cholesterol within the animal cell membrane

(a) Movement of phospholipids Fig. 7-5a Lateral movement (107 times per second) Flip-flop ( once per month) Figure 7.5a The fluidity of membranes (a) Movement of phospholipids

Membrane proteins Mixed proteins after 1 hour Mouse cell Human cell Fig. 7-6 RESULTS Membrane proteins Mixed proteins after 1 hour Mouse cell Figure 7.6 Do membrane proteins move? Human cell Hybrid cell

Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails Fig. 7-5b Fluid Viscous Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails Figure 7.5b The fluidity of membranes (b) Membrane fluidity

(c) Cholesterol within the animal cell membrane Fig. 7-5c Cholesterol Figure 7.5c The fluidity of membranes (c) Cholesterol within the animal cell membrane

Fig. 7-7 Fibers of extracellular matrix (ECM) Glyco- Carbohydrate protein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Figure 7.7 The detailed structure of an animal cell’s plasma membrane, in a cutaway view Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE

EXTRACELLULAR N-terminus SIDE C-terminus CYTOPLASMIC SIDE  Helix Fig. 7-8 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 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)

(b) Enzymatic activity (c) Signal transduction Fig. 7-9ac Signaling molecule Enzymes Receptor Figure 7.9a–c Some functions of membrane proteins ATP Signal transduction (a) Transport (b) Enzymatic activity (c) Signal transduction

(d) Cell-cell recognition (e) Intercellular joining (f) Attachment to Fig. 7-9df Glyco- protein Figure 7.9d–f Some functions of membrane proteins (d) Cell-cell recognition (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM)

ER 1 Transmembrane glycoproteins Secretory protein Glycolipid Golgi 2 Fig. 7-10 ER 1 Transmembrane glycoproteins Secretory protein Glycolipid Golgi apparatus 2 Vesicle Figure 7.10 Synthesis of membrane components and their orientation on the resulting membrane 3 Plasma membrane: Cytoplasmic face 4 Extracellular face Transmembrane glycoprotein Secreted protein Membrane glycolipid

Membrane (cross section) Fig. 7-11 Molecules of dye Membrane (cross section) WATER Net diffusion Net diffusion Equilibrium (a) Diffusion of one solute Figure 7.11 The diffusion of solutes across a membrane Net diffusion Net diffusion Equilibrium Net diffusion Net diffusion Equilibrium (b) Diffusion of two solutes

Membrane (cross section) Fig. 7-11a 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 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 Lower concentration of solute (sugar) Higher concentration of sugar Same concentration of sugar H2O Selectively permeable membrane Figure 7.12 Osmosis Osmosis

cell cell Hypotonic solution Isotonic solution Hypertonic solution H2O Fig. 7-13 Hypotonic solution Isotonic solution Hypertonic solution H2O H2O H2O H2O (a) Animal cell Lysed Normal Shriveled H2O H2O H2O H2O Figure 7.13 The water balance of living cells (b) Plant cell Turgid (normal) Flaccid Plasmolyzed

(a) A contractile vacuole fills with fluid that enters from Fig. 7-14 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.

Channel protein Solute (a) A channel protein Solute Carrier protein Fig. 7-15 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

Cytoplasmic Na+ binds to Fig. 7-16-1 EXTRACELLULAR FLUID [Na+] high [K+] low Na+ Na+ [Na+] low Na+ Figure 7.16, 1 The sodium-potassium pump: a specific case of active transport CYTOPLASM [K+] high Cytoplasmic Na+ binds to the sodium-potassium pump. 1

Na+ binding stimulates Fig. 7-16-2 Na+ Na+ Na+ ATP P Figure 7.16, 2 The sodium-potassium pump: a specific case of active transport ADP Na+ binding stimulates phosphorylation by ATP. 2

Phosphorylation causes the protein to change its Fig. 7-16-3 Na+ Na+ Na+ Figure 7.16, 3 The sodium-potassium pump: a specific case of active transport P Phosphorylation causes the protein to change its shape. Na+ is expelled to the outside. 3

extracellular side and triggers release of the phosphate group. Fig. 7-16-4 K+ K+ P Figure 7.16, 4 The sodium-potassium pump: a specific case of active transport P K+ binds on the extracellular side and triggers release of the phosphate group. 4

restores the protein’s original shape. Fig. 7-16-5 K+ K+ Figure 7.16, 5 The sodium-potassium pump: a specific case of active transport Loss of the phosphate restores the protein’s original shape. 5

K+ is released, and the cycle repeats. 6 K+ K+ Fig. 7-16-6 Figure 7.16, 6 The sodium-potassium pump: a specific case of active transport K+ K+ is released, and the cycle repeats. 6

1 2 3 6 5 4 EXTRACELLULAR FLUID [Na+] high Na+ [K+] low Na+ Na+ Na+ Fig. 7-16-7 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 Passive transport Active transport ATP Diffusion Facilitated diffusion Figure 7.17 Review: passive and active transport

– EXTRACELLULAR FLUID + ATP – + H+ H+ Proton pump H+ – + H+ H+ H+ – + Fig. 7-18 – EXTRACELLULAR FLUID + ATP – + H+ H+ Proton pump H+ – + H+ H+ H+ Figure 7.18 An electrogenic pump – + CYTOPLASM H+ – +

Fig. 7-20 Figure 7.20 Endocytosis in animal cells PHAGOCYTOSIS EXTRACELLULAR FLUID CYTOPLASM 1 µm Pseudopodium Pseudopodium of amoeba “Food”or other particle Bacterium Food vacuole Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM) PINOCYTOSIS 0.5 µm Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM) Vesicle RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein Receptor Coated vesicle Figure 7.20 Endocytosis in animal cells Coated pit Ligand A coated pit and a coated vesicle formed during receptor- mediated endocytosis (TEMs) Coat protein Plasma membrane 0.25 µm

PHAGOCYTOSIS CYTOPLASM 1 µm EXTRACELLULAR FLUID Pseudopodium Fig. 7-20a 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)

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

Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit Fig. 7-20c 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

Facilitated diffusion Fig. 7-UN1 Passive transport: Facilitated diffusion Channel protein Carrier protein

Fig. 7-UN2 Active transport: ATP

Environment: 0.01 M sucrose “Cell” 0.01 M glucose 0.01 M fructose Fig. 7-UN3 Environment: 0.01 M sucrose 0.01 M glucose 0.01 M fructose “Cell” 0.03 M sucrose 0.02 M glucose

Fig. 7-UN4

You should now be able to: Define the following terms: amphipathic molecules, aquaporins, diffusion Explain how membrane fluidity is influenced by temperature and membrane composition Distinguish between the following pairs or sets of terms: peripheral and integral membrane proteins; channel and carrier proteins; osmosis, facilitated diffusion, and active transport; hypertonic, hypotonic, and isotonic solutions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Explain how transport proteins facilitate diffusion Explain how an electrogenic pump creates voltage across a membrane, and name two electrogenic pumps Explain how large molecules are transported across a cell membrane Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings