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Membrane Transport and Cell Signaling

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Presentation on theme: "Membrane Transport and Cell Signaling"— Presentation transcript:

1 Membrane Transport and Cell Signaling
5 Membrane Transport and Cell Signaling

2 Overview: Life at the Edge
Plasma membrane exhibits selective permeability, some substances cross it more easily than others Video: Membrane and Aquaporin © 2014 Pearson Education, Inc. 2

3 Figure 5.1 Figure 5.1 How do cell membrane proteins help regulate chemical traffic? © 2014 Pearson Education, Inc. 3

4 CONCEPT 5.1: Cellular membranes are fluid mosaics of lipids and proteins
Phospholipids are amphipathic, containing hydrophobic and hydrophilic regions © 2014 Pearson Education, Inc. 4

5 EXTRACELLULAR SIDE OF MEMBRANE
Figure 5.2 Fibers of extra- cellular matrix (ECM) Glyco- protein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Figure 5.2 Current model of an animal cell’s plasma membrane (cutaway view) Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE © 2014 Pearson Education, Inc. 5

6 fluid mosaic model -membrane is a mosaic of protein molecules bobbing in phospholipids bilayer
© 2014 Pearson Education, Inc. 6

7 Lipid Bilayer hydrophilic parts hydrophobic parts fluid fluid
one layer of lipids one layer of lipids b cross-section through lipid bilayer a Fig. 5.3, pg. 76

8 Hydrophilic head WATER WATER Hydrophobic tail Figure 5.3
Figure 5.3 Phospholipid bilayer (cross section) Hydrophobic tail © 2014 Pearson Education, Inc. 8

9 cytoskeletal proteins just beneath the plasma membrane
Fluid Mosaic Model passive transporter recognition protein phospholipid adhesion protein cholesterol receptor Lipid bilayer active transporter (ATPase pump) active transporter (calcium pump) Cytoplasm Plasma Membrane cytoskeletal proteins just beneath the plasma membrane Fig. 5.4, pg. 77

10 Results Membrane proteins Mixed proteins after 1 hour Mouse cell
Figure 5.4-3 Results Membrane proteins Mixed proteins after 1 hour Mouse cell Human cell Figure Inquiry: Do membrane proteins move? (step 3) Hybrid cell © 2014 Pearson Education, Inc. 10

11 Unsaturated tails prevent packing. Saturated tails pack together.
Figure 5.5 Fluid Viscous Unsaturated tails prevent packing. Saturated tails pack together. (a) Unsaturated versus saturated hydrocarbon tails (b) Cholesterol reduces membrane fluidity at moderate temperatures, but at low temperatures hinders solidification. Figure 5.5 Factors that affect membrane fluidity Cholesterol © 2014 Pearson Education, Inc. 11

12 Membrane Proteins and Their Functions
A membrane is a collage of different proteins, Proteins determine most of membrane’s functions Integral proteins penetrate hydrophobic interior Peripheral proteins are loosely bound to the surface © 2014 Pearson Education, Inc. 12

13 N-terminus EXTRACELLULAR SIDE  helix CYTOPLASMIC SIDE C-terminus
Figure 5.6 N-terminus EXTRACELLULAR SIDE Figure 5.6 The structure of a transmembrane protein  helix CYTOPLASMIC SIDE C-terminus © 2014 Pearson Education, Inc. 13

14 Six major functions of membrane proteins Transport Enzymatic activity
Attachment to the cytoskeleton and extracellular matrix (ECM) Cell-cell recognition Intercellular joining Signal transduction © 2014 Pearson Education, Inc. 14

15 major functions of membrane proteins
Figure 5.7a Enzymes ATP Figure 5.7a Some functions of membrane proteins (part 1: transport, enzymatic activity, and attachment to the cytoskeleton and ECM) (a) Transport (b) Enzymatic activity (c) Attachment to the cytoskeleton and extra- cellular matrix (ECM) © 2014 Pearson Education, Inc. 15

16 major functions of membrane proteins
Figure 5.7a Signaling molecule Receptor Glyco- protein Figure 5.7b Some functions of membrane proteins (part 2: cell-cell recognition, intercellular joining, and signal transduction) (d) Cell-cell recognition (e) Intercellular joining (f) Signal transduction © 2014 Pearson Education, Inc. 16

17 Transmembrane Secretory glycoproteins protein Golgi apparatus Vesicle
Figure 5.8 Transmembrane glycoproteins Secretory protein Golgi apparatus Vesicle ER ER lumen Glycolipid Figure 5.8 Synthesis of membrane components and their orientation in the membrane Plasma membrane: Cytoplasmic face Transmembrane glycoprotein Extracellular face Secreted protein Membrane glycolipid © 2014 Pearson Education, Inc. 17

18 The Permeability of the Lipid Bilayer
Hydrophobic (nonpolar) molecules dissolve in lipid bilayer and cross it easily Polar molecules, such as sugars, do not © 2014 Pearson Education, Inc. 18

19 Transport Proteins Transport proteins allow passage of hydrophilic substances Some -channel proteins- have a channel for certain substances aquaporins are channel proteins for passage of water carrier proteins are transport proteins that bind to molecules and change shape to transport them © 2014 Pearson Education, Inc. 19

20 Diffusion Stepped Art Fig. 5.7a, p.80

21 Diffusion Stepped Art Fig. 5.7b, p.80

22 CONCEPT 5.3: Passive transport is diffusion of a substance across a membrane with no energy investment dynamic equilibrium, as many molecules cross the membrane in one direction as in the other © 2014 Pearson Education, Inc. 22

23 Membrane (cross section)
Figure 5.9 Molecules of dye Membrane (cross section) WATER Net diffusion Net diffusion Equilibrium (a) Diffusion of one solute Figure 5.9 The diffusion of solutes across a synthetic membrane Net diffusion Net diffusion Equilibrium Net diffusion Net diffusion Equilibrium (b) Diffusion of two solutes © 2014 Pearson Education, Inc. 23

24 Diffusion Rate depends upon…
Steepness of c gradient Molecular size Temp Electrical or pressure gradients

25 Osmosis Animation: Membrane Selectivity Animation: Osmosis 25

26 Lower concentration of solute (sugar) Higher concentration of solute
Figure 5.10 Lower concentration of solute (sugar) Higher concentration of solute More similar concen- trations of solute Sugar molecule H2O Selectively permeable membrane Figure 5.10 Osmosis Osmosis © 2014 Pearson Education, Inc. 26

27 Water Balance of Cells Without Walls
Tonicity ability of a solution to cause a cell to gain or lose water Isotonic : Solute concentration is equal on both sides of membrane Hypertonic : Solute concentration is greater than other side of membrane Hypotonic : Solute concentration is less than other side of membrane Video: Turgid Elodea © 2014 Pearson Education, Inc. 27

28 Hypotonic Isotonic Hypertonic H2O H2O H2O H2O Animal cell Lysed Normal
Figure 5.11 Hypotonic Isotonic Hypertonic H2O H2O H2O H2O Animal cell Lysed Normal Shriveled Cell wall H2O H2O H2O H2O Figure 5.11 The water balance of living cells Plant cell Turgid (normal) Flaccid Plasmolyzed © 2014 Pearson Education, Inc. 28

29 Osmoregulation, the control of solute c’s and water balance
The protist Paramecium caudatum, which is hypertonic to its pondwater environment, has a contractile vacuole that can pump excess water out of the cell Video: Paramecium Vacuole © 2014 Pearson Education, Inc. 29

30 50 m Contractile vacuole Figure 5.12
Figure 5.12 The contractile vacuole of Paramecium caudatum © 2014 Pearson Education, Inc. 30

31 Hypotonic Isotonic Hypertonic H2O H2O H2O H2O Animal cell Lysed Normal
Figure 5.11 Hypotonic Isotonic Hypertonic H2O H2O H2O H2O Animal cell Lysed Normal Shriveled Cell wall H2O H2O H2O H2O Figure 5.11 The water balance of living cells Plant cell Turgid (normal) Flaccid Plasmolyzed © 2014 Pearson Education, Inc. 31

32 EXTRA- CELLULAR FLUID A channel protein Channel protein Solute
Figure 5.13 EXTRA- CELLULAR FLUID A channel protein Channel protein Solute CYTOPLASM Figure 5.13 Two types of transport proteins that carry out facilitated diffusion Carrier protein Solute (b) A carrier protein © 2014 Pearson Education, Inc. 32

33 The Need for Energy in Active Transport
Active transport moves substances against c gradients requires energy © 2014 Pearson Education, Inc. 33

34 Sodium-Potassium Pump Figure 5.14
EXTRACELLULAR FLUID [Na] high [K] low [Na] low 1 CYTOPLASM [K] high 2 ADP 6 3 Figure 5.14 The sodium-potassium pump: a specific case of active transport 5 4 © 2014 Pearson Education, Inc. 34

35 Facilitated diffusion
Figure 5.15 Passive transport Active transport Figure 5.15 Review: passive and active transport Diffusion Facilitated diffusion © 2014 Pearson Education, Inc. 35

36 Proton pump – enhances electrochemical gradient Figure 5.16
EXTRACELLULAR FLUID Proton pump Figure 5.16 A proton pump CYTOPLASM © 2014 Pearson Education, Inc. 36

37 Cotransport: Coupled Transport by a Membrane Protein
Figure 5.17 Proton pump Figure 5.17 Cotransport: active transport driven by a concentration gradient Sucrose-H cotransporter Diffusion of H Sucrose Sucrose © 2014 Pearson Education, Inc. 37

38 CONCEPT 5.5: Bulk transport Exocytosis and endocytosis
exocytosis, transport vesicles migrate to membrane, fuse with it, and release their contents Endocytosis- reversal of exocytosis- cell takes in matter by forming new vesicles 3 types Phagocytosis (“cellular eating”) Pinocytosis (“cellular drinking”) Receptor-mediated endocytosis © 2014 Pearson Education, Inc. 38

39 Receptor-Mediated Endocytosis
Figure 5.18 Receptor-Mediated Endocytosis Phagocytosis Pinocytosis EXTRACELLULAR FLUID Solutes Pseudopodium Plasma membrane Receptor Coat protein “Food” or other particle Coated pit Figure 5.18 Exploring endocytosis in animal cells Coated vesicle Food vacuole CYTOPLASM © 2014 Pearson Education, Inc. 39

40 An amoeba engulfing a bacterium via phagocytosis (TEM)
Figure 5.18a Phagocytosis EXTRACELLULAR FLUID Pseudopodium of amoeba Solutes Pseudopodium Bacterium 1 m Food vacuole “Food” or other particle An amoeba engulfing a bacterium via phagocytosis (TEM) Figure 5.18a Exploring endocytosis in animal cells (part 1: phagocytosis) Food vacuole CYTOPLASM © 2014 Pearson Education, Inc. 40

41 0.25 m Pinocytosis Plasma membrane Coat protein
Figure 5.18b Pinocytosis Plasma membrane 0.25 m Coat protein Pinocytotic vesicles forming (TEMs) Coated pit Figure 5.18b Exploring endocytosis in animal cells (part 2: pinocytosis) Coated vesicle © 2014 Pearson Education, Inc. 41

42 0.25 m Receptor-Mediated Endocytosis Coat Plasma protein membrane
Figure 5.18c Receptor-Mediated Endocytosis Plasma membrane Coat protein Receptor 0.25 m Figure 5.18c Exploring endocytosis in animal cells (part 3: receptor-mediated endocytosis) Top: A coated pit Bottom: A coated vesicle forming during receptor- mediated endocytosis (TEMs) © 2014 Pearson Education, Inc. 42

43 Long-distance signaling
Figure 5.19 Local signaling Long-distance signaling Target cell Electrical signal along nerve cell triggers release of neuro- transmitter. Blood vessel Endocrine cell Secreting cell Neurotransmitter diffuses across synapse. Secretory vesicle Hormone travels in bloodstream. Target cell specifically binds hormone. Local regulator diffuses through extracellular fluid. Target cell is stimulated. (a) Paracrine signaling Figure 5.19 Local and long-distance cell signaling by secreted molecules in animals (b) Synaptic signaling (c) Endocrine (hormonal) signaling © 2014 Pearson Education, Inc. 43

44 The Three Stages of Cell Signaling: A Preview
cells receiving signals undergo… Reception Transduction Response Animation: Signaling Overview © 2014 Pearson Education, Inc. 44

45 EXTRACELLULAR FLUID CYTOPLASM Plasma membrane Reception Transduction
Figure EXTRACELLULAR FLUID CYTOPLASM Plasma membrane Reception Transduction Response Receptor Activation Relay molecules Figure Overview of cell signaling (step 3) Signaling molecule © 2014 Pearson Education, Inc. 45

46 Small Molecules and Ions as Second Messengers
Second messengers are nonprotein, water-soluble molecules or ions that spread through cell by diffusion Cyclic AMP and calcium ions are examples © 2014 Pearson Education, Inc. 46

47 First messenger (signaling molecule such as epinephrine) Adenylyl
Figure 5.25 First messenger (signaling molecule such as epinephrine) Adenylyl cyclase G protein G protein-coupled receptor Second messenger Figure 5.25 cAMP as a second messenger in a G protein signaling pathway Protein kinase A Cellular responses © 2014 Pearson Education, Inc. 47

48 Growth factor Reception Receptor Transduction CYTOPLASM Inactive
Figure 5.26 Growth factor Reception Receptor Phosphorylation cascade Transduction CYTOPLASM Inactive transcription factor Active transcription factor Figure 5.26 Nuclear response to a signal: the activation of a specific gene by a growth factor Response DNA Gene NUCLEUS mRNA © 2014 Pearson Education, Inc. 48

49 Growth factor Reception Receptor Transduction CYTOPLASM Inactive
Figure 5.26a Growth factor Reception Receptor Phosphorylation cascade Transduction CYTOPLASM Figure 5.26a Nuclear response to a signal: the activation of a specific gene by a growth factor (part 1) Inactive transcription factor © 2014 Pearson Education, Inc. 49

50 Transduction CYTOPLASM Inactive Active transcription transcription
Figure 5.26b Phosphorylation cascade Transduction CYTOPLASM Inactive transcription factor Active transcription factor Response Figure 5.26b Nuclear response to a signal: the activation of a specific gene by a growth factor (part 2) DNA Gene NUCLEUS mRNA © 2014 Pearson Education, Inc. 50

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