1. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 11 Cell Communication

2. Overview: The Cellular Internet Cell-to-cell communication is essential for multicellular organisms Biologists have discovered some universal mechanisms of cellular regulation The combined effects of multiple signals determine cell response For example, the dilation of blood vessels is controlled by multiple molecules Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. Fig. 11-1

4. Concept 11.1: External signals are converted to responses within the cell Microbes: – are a window on the role of cell signaling in the evolution of life Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

5. Evolution of Cell Signaling A signal transduction pathway: – Is a series of steps by which: – A signal on a cell’s surface is converted into a specific cellular response Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. Fig. 11-2 Receptor  factor a factor a   a Exchange of mating factors Yeast cell, mating type a Yeast cell, mating type  Mating New a/  cell a/  1 2 3

7. Pathway similarities suggest that: – Ancestral signaling molecules: Evolved in prokaryotes Modified later in eukaryotes Signaling molecules concentration in bacteria: – Allow them to detect population density Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8. Fig. 11-3 Individual rod- shaped cells Spore-forming structure (fruiting body) Aggregation in process Fruiting bodies 0.5 mm 1 3 2

9. Local and Long-Distance Signaling Cellular communication can be by: – Chemical messengers – Direct cytoplasmic connection thru: Cell junctions of adjacent cells – Direct contact, or cell-cell recognition Short distance communication uses: – Local messenger molecules for Long distance communication uses: – Hormones for -distance signaling Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10. Fig. 11-4 Plasma membranes Gap junctions between animal cells (a) Cell junctions Plasmodesmata between plant cells (b) Cell-cell recognition

11. Fig. 11-5 Local signaling Target cell Secreting cell Secretory vesicle Local regulator diffuses through extracellular fluid (a) Paracrine signaling(b) Synaptic signaling Target cell is stimulated Neurotransmitter diffuses across synapse Electrical signal along nerve cell triggers release of neurotransmitter Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling

12. Fig. 11-5ab Local signaling Target cell Secretory vesicle Secreting cell Local regulator diffuses through extracellular fluid (a) Paracrine signaling (b) Synaptic signaling Target cell is stimulated Neurotransmitter diffuses across synapse Electrical signal along nerve cell triggers release of neurotransmitter

13. Fig. 11-5c Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling

14. The Three Stages of Cell Signaling: A Preview Cells receiving signals go through 3 processes: – Reception – Transduction – Response Animation: Overview of Cell Signaling Animation: Overview of Cell Signaling Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. Fig. 11-6-1 Reception 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM 1 Receptor

16. Fig. 11-6-2 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM Transduction 2 Relay molecules in a signal transduction pathway Reception 1 Receptor

17. Fig. 11-6-3 EXTRACELLULAR FLUID Plasma membrane CYTOPLASM Receptor Signaling molecule Relay molecules in a signal transduction pathway Activation of cellular response TransductionResponse 2 3 Reception 1

18. Concept 11.2: Reception: A signal molecule binds to a receptor protein, causing it to change shape A signaling molecule is called a ligand Most signal receptors are plasma membrane proteins Binding between a ligand & receptor is highly specific A receptor shape change is often the initial transduction of the signal Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

19. Receptors in the Plasma Membrane There are three main membrane receptor types: – G protein-coupled receptors – Receptor tyrosine kinases – Ion channel receptors Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

20. G protein-coupled receptor: – A plasma membrane receptor – Works with the help of a G protein The G protein: – Acts as an on/off switch – Inactivated by binding to GDP Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

21. Fig. 11-7a Signaling-molecule binding site Segment that interacts with G proteins G protein-coupled receptor

22. Fig. 11-7b G protein-coupled receptor Plasma membrane Enzyme G protein (inactive) GDP CYTOPLASM Activated enzyme GTP Cellular response GDP P i Activated receptor GDP GTP Signaling molecule Inactive enzyme 1 2 3 4

23. Receptor tyrosine kinases: – Are membrane receptors – Attach phosphates to tyrosines – A receptor tyrosine kinase can trigger multiple signal transduction pathways at once Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24. Fig. 11-7c Signaling molecule (ligand) Ligand-binding site  Helix Tyrosines Tyr Receptor tyrosine kinase proteins CYTOPLASM Signaling molecule Tyr Dimer Activated relay proteins Tyr P P P P P P Cellular response 1 Cellular response 2 Inactive relay proteins Activated tyrosine kinase regions Fully activated receptor tyrosine kinase 6 6 ADP ATP Tyr P P P P P P 1 2 3 4

25. A ligand-gated ion channel receptor: – A ligand-gated receptor – Acts as a gate for ion movement Signal molecule (ligand) binding results in: – Change in receptor shape – Creation of a channel in the receptor – Transport of specific ions, e.g. Na + or Ca 2+ Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

26. Fig. 11-7d Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate open Cellular response Gate closed 3 2 1

27. Intracellular Receptors Intracellular Receptors: – Found in the cytosol or nucleus of target cells Small or hydrophobic chemical messengers: – Can readily cross the membrane – Can activate receptors – Examples of hydrophobic messengers: Steroid & thyroid hormones of animals An activated hormone-receptor complex: – Can act as a transcription factor – Turning on specific genes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

28. Fig. 11-8-1 Hormone (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID DNA NUCLEUS CYTOPLASM

29. Fig. 11-8-2 Receptor protein Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM

30. Fig. 11-8-3 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM

31. Fig. 11-8-4 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA mRNA NUCLEUS CYTOPLASM

32. Fig. 11-8-5 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA NUCLEUS New protein CYTOPLASM

33. 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 & regulation of the cellular response Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

34. 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

35. Protein Phosphorylation and Dephosphorylation In many pathways, signals are transmitted by cascades of protein phosphorylations Protein kinases: – Transfer phosphates from ATP to protein – The process called phosphorylation Protein phosphatases: – Remove the phosphates from proteins – The process called dephosphorylation The phosphorylation-dephosphorylation system: – Acts as a molecular switch – Turns activities on and off Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

36. Fig. 11-9 Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 ATP ADP Active protein kinase 2 P P PP Inactive protein kinase 3 ATP ADP Active protein kinase 3 P P PP i ATP ADP P Active protein PP P i Inactive protein Cellular response Phosphorylation cascade i

37. End of The Chapter