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LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert.

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Presentation on theme: "LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert."— Presentation transcript:

1 LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Cell Communication Chapter 11

2 Local and Long-Distance Signaling Cells in a multicellular organism communicate by chemical messengers Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells In local signaling, animal cells may communicate by direct contact, or cell-cell recognition © 2011 Pearson Education, Inc.

3 Figure 11.4 Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells (a) Cell junctions (b) Cell-cell recognition

4 In many other cases, animal cells communicate using local regulators, messenger molecules that travel only short distances In long-distance signaling, plants and animals use chemicals called hormones The ability of a cell to respond to a signal depends on whether or not it has a receptor specific to that signal © 2011 Pearson Education, Inc.

5 Figure 11.5 Local signaling Long-distance signaling Target cell Secreting cell Secretory vesicle Local regulator diffuses through extracellular fluid. (a) Paracrine signaling(b) Synaptic signaling Electrical signal along nerve cell triggers release of neurotransmitter. Neurotransmitter diffuses across synapse. Target cell is stimulated. Endocrine cell Blood vessel Hormone travels in bloodstream. Target cell specifically binds hormone. (c) Endocrine (hormonal) signaling

6 The Three Stages of Cell Signaling: A Preview Cells receiving signals go through three processes –Reception –Transduction –Response © 2011 Pearson Education, Inc. Animation: Overview of Cell Signaling

7 Figure Plasma membrane EXTRACELLULAR FLUID CYTOPLASM Reception Receptor Signaling molecule 1

8 Figure Plasma membrane EXTRACELLULAR FLUID CYTOPLASM ReceptionTransduction Receptor Signaling molecule Relay molecules in a signal transduction pathway 2 1

9 Figure Plasma membrane EXTRACELLULAR FLUID CYTOPLASM ReceptionTransduction Response Receptor Signaling molecule Activation of cellular response Relay molecules in a signal transduction pathway 3 2 1

10 Concept 11.2: Reception: A signaling molecule binds to a receptor protein, causing it to change shape The binding between a signal molecule (ligand) and receptor is highly specific A shape change in a receptor is often the initial transduction of the signal Most signal receptors are plasma membrane proteins © 2011 Pearson Education, Inc.

11 Receptors in the Plasma Membrane The main types of membrane receptors –G protein-coupled receptors –Ion channel receptors © 2011 Pearson Education, Inc.

12 G-protein-coupled receptor (GPCRs) are the largest family of cell-surface receptors A GPCR is a plasma membrane receptor that works with the help of a G protein The G protein acts as an on/off switch: If GDP is bound to the G protein, the G protein is inactive © 2011 Pearson Education, Inc.

13 Figure 11.7b G protein-coupled receptor Plasma membrane G protein (inactive) CYTOPLASM Enzyme Activated receptor Signaling molecule Inactive enzyme Activated enzyme Cellular response GDP GTP GDP GTP P i GDP

14 A ligand-gated ion channel receptor acts as a gate when the receptor changes shape When a signal molecule binds as a ligand to the receptor, the gate allows specific ions, such as Na + or Ca 2+, through a channel in the receptor © 2011 Pearson Education, Inc.

15 Figure 11.7d Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate open Cellular response Gate closed

16 Intracellular Receptors Steroids Intracellular receptor proteins are found in the cytosol or nucleus of target cells Small or hydrophobic chemical messengers can readily cross the membrane and activate receptors Examples of hydrophobic messengers are the steroid and thyroid hormones of animals An activated hormone-receptor complex can act as a transcription factor, turning on specific genes © 2011 Pearson Education, Inc.

17 Figure Hormone (testosterone) Receptor protein Plasma membrane DNA NUCLEUS CYTOPLASM EXTRACELLULAR FLUID

18 Figure Hormone (testosterone) Receptor protein Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM EXTRACELLULAR FLUID

19 Figure Hormone (testosterone) Receptor protein Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM EXTRACELLULAR FLUID

20 Figure Hormone (testosterone) Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA NUCLEUS CYTOPLASM EXTRACELLULAR FLUID

21 Figure Hormone (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID Hormone- receptor complex DNA mRNA NUCLEUS CYTOPLASM New protein

22 Concept 11.3: Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell Signal transduction usually involves multiple steps Multistep pathways can amplify a signal: A few molecules can produce a large cellular response Multistep pathways provide more opportunities for coordination and regulation of the cellular response © 2011 Pearson Education, Inc.

23 Signal Transduction Pathways The molecules that relay a signal from receptor to response are mostly proteins Like falling dominoes, the receptor activates another protein, which activates another, and so on, until the protein producing the response is activated At each step, the signal is transduced into a different form, usually a shape change in a protein © 2011 Pearson Education, Inc.

24 Protein Phosphorylation and Dephosphorylation In many pathways, the signal is transmitted by a cascade of protein phosphorylations Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation © 2011 Pearson Education, Inc.

25 Protein phosphatases remove the phosphates from proteins, a process called dephosphorylation This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off or up or down, as required © 2011 Pearson Education, Inc.

26 Receptor Signaling molecule Activated relay molecule Phosphorylation cascade Inactive protein kinase 1 Active protein kinase 1 Active protein kinase 2 Active protein kinase 3 Inactive protein kinase 2 Inactive protein kinase 3 Inactive protein Active protein Cellular response ATP ADP ATP ADP ATP ADP PP P P P P i Figure 11.10

27 Activated relay molecule Phosphorylation cascade Inactive protein kinase 1 Active protein kinase 1 Active protein kinase 2 Active protein kinase 3 Inactive protein kinase 2 Inactive protein kinase 3 Inactive protein Active protein ATP ADP ATP ADP ATP ADP PP P P P i P Figure 11.10a

28 Small Molecules and Ions as Second Messengers The extracellular signal molecule (ligand) that binds to the receptor is a pathway’s “first messenger” Second messengers are small, nonprotein, water- soluble molecules or ions that spread throughout a cell by diffusion Second messengers participate in pathways initiated by GPCRs and RTKs Cyclic AMP and calcium ions are common second messengers © 2011 Pearson Education, Inc.

29 Cyclic AMP Cyclic AMP (cAMP) is one of the most widely used second messengers Adenylyl cyclase, an enzyme in the plasma membrane, converts ATP to cAMP in response to an extracellular signal © 2011 Pearson Education, Inc.

30 Figure Adenylyl cyclase Phosphodiesterase Pyrophosphate AMP H2OH2O ATP P i P cAMP

31 Figure 11.11a Adenylyl cyclase Pyrophosphate ATP P i P cAMP

32 Figure 11.11b Phosphodiesterase AMP H2OH2O cAMP H2OH2O

33 Many signal molecules trigger formation of cAMP Other components of cAMP pathways are G proteins, G protein-coupled receptors, and protein kinases cAMP usually activates protein kinase A, which phosphorylates various other proteins Further regulation of cell metabolism is provided by G-protein systems that inhibit adenylyl cyclase © 2011 Pearson Education, Inc.

34 Figure G protein First messenger (signaling molecule such as epinephrine) G protein-coupled receptor Adenylyl cyclase Second messenger Cellular responses Protein kinase A GTP ATP cAMP

35 Calcium Ions Calcium ions (Ca 2+ ) act as a second messenger in many pathways Calcium is an important second messenger because cells can regulate its concentration © 2011 Pearson Education, Inc.

36 Figure Mitochondrion EXTRACELLULAR FLUID Plasma membrane Ca 2  pump Nucleus CYTOSOL Ca 2  pump Endoplasmic reticulum (ER) ATP Low [Ca 2  ] High [Ca 2  ] Key

37 Concept 11.4: Response: Cell signaling leads to regulation of transcription or cytoplasmic activities The cell’s response to an extracellular signal is sometimes called the “output response” © 2011 Pearson Education, Inc.

38 Figure Growth factor Receptor Reception Transduction CYTOPLASM Response Inactive transcription factor Active transcription factor DNA NUCLEUS mRNA Gene Phosphorylation cascade P

39 Figure Reception Transduction Response Binding of epinephrine to G protein-coupled receptor (1 molecule) Inactive G protein Active G protein (10 2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10 2 ) ATP Cyclic AMP (10 4 ) Inactive protein kinase A Active protein kinase A (10 4 ) Inactive phosphorylase kinase Active phosphorylase kinase (10 5 ) Inactive glycogen phosphorylase Active glycogen phosphorylase (10 6 ) Glycogen Glucose 1-phosphate (10 8 molecules)

40 Concept 11.5: Apoptosis integrates multiple cell-signaling pathways Apoptosis is programmed or controlled cell suicide Components of the cell are chopped up and packaged into vesicles that are digested by scavenger cells Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells © 2011 Pearson Education, Inc.

41 Figure Mitochondrion Ced-9 protein (active) inhibits Ced-4 activity Receptor for death- signaling molecule Ced-4 Ced-3 Inactive proteins (a) No death signal Death- signaling molecule Ced-9 (inactive) Cell forms blebs Active Ced-4 Active Ced-3 Other proteases Nucleases Activation cascade (b) Death signal

42 Figure 11.21a Mitochondrion Ced-9 protein (active) inhibits Ced-4 activity Receptor for death- signaling molecule Ced-4 Ced-3 Inactive proteins (a) No death signal

43 Death- signaling molecule Ced-9 (inactive) Cell forms blebs Active Ced-4 Active Ced-3 Other proteases Nucleases Activation cascade (b) Death signal Figure 11.21b

44 Figure Interdigital tissue Cells undergoing apoptosis Space between digits 1 mm


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