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Chapter 11 Cell Communication. Overview: The Cellular Internet Cell-to-cell communication is essential for multicellular organisms Biologists have discovered.

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Presentation on theme: "Chapter 11 Cell Communication. Overview: The Cellular Internet Cell-to-cell communication is essential for multicellular organisms Biologists have discovered."— Presentation transcript:

1 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 Cell- cell interactions

4 You should now be able to: 1.Describe the nature of a ligand-receptor interaction and state how such interactions initiate a signal-transduction system 2.Compare and contrast G protein-coupled receptors, tyrosine kinase receptors, and ligand- gated ion channels 3.List two advantages of a multistep pathway in the transduction stage of cell signaling 4.Explain how an original signal molecule can produce a cellular response when it may not even enter the target cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

5 5.Define the term second messenger; briefly describe the role of these molecules in signaling pathways 6.Explain why different types of cells may respond differently to the same signal molecule 7.Describe the role of apoptosis in normal development and degenerative disease in vertebrates Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6 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

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

8 The Three Stages of Cell Signaling: A Preview Earl W. Sutherland discovered how the hormone epinephrine acts on cells Sutherland suggested that cells receiving signals went through three processes: – Reception – Transduction – Response Animation: Overview of Cell Signaling Animation: Overview of Cell Signaling Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

9 Concept 11.2: Reception: A signal 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10 Fig Reception 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM 1 Receptor

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

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

13 Receptors in the Plasma Membrane Most water-soluble signal molecules bind to specific sites on receptor proteins in the plasma membrane There are three main types of membrane receptors: – G protein-coupled receptors – Receptor tyrosine kinases – Ion channel receptors Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

14 A G protein-coupled receptor 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15 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

16 Receptor tyrosine kinases are membrane receptors that 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

17 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

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

19 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

20 Intracellular Receptors Some receptor proteins are intracellular, 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

21 Fig Hormone (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID DNA NUCLEUS CYTOPLASM

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

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

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

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

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

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

28 Fig 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

29 Small Molecules and Ions as Second Messengers The extracellular signal molecule 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 G protein-coupled receptors and receptor tyrosine kinases Cyclic AMP and calcium ions are common second messengers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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

31 Adenylyl cyclase Fig Pyrophosphate P P i ATP cAMP Phosphodiesterase AMP

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

33 First messenger Fig G protein Adenylyl cyclase GTP ATP cAMP Second messenger Protein kinase A G protein-coupled receptor Cellular responses

34 Calcium Ions and Inositol Triphosphate (IP 3 ) Calcium ions (Ca 2+ ) act as a second messenger in many pathways Calcium is an important second messenger because cells can regulate its concentration Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

35 EXTRACELLULAR FLUID Fig ATP Nucleus Mitochondrion Ca 2+ pump Plasma membrane CYTOSOL Ca 2+ pump Endoplasmic reticulum (ER) Ca 2+ pump ATP Key High [Ca 2+ ] Low [Ca 2+ ]

36 A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol Pathways leading to the release of calcium involve inositol triphosphate (IP 3 ) and diacylglycerol (DAG) as additional second messengers Animation: Signal Transduction Pathways Animation: Signal Transduction Pathways Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

37 Fig EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein GTP G protein-coupled receptor Phospholipase C PIP 2 IP 3 DAG (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL

38 Fig G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase C PIP 2 DAG IP 3 (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL Ca 2+ (second messenger) GTP

39 Fig G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase C PIP 2 DAG IP 3 (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL Various proteins activated Cellular responses Ca 2+ (second messenger) GTP

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

41 Fig 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)

42 Fig a RESULTS Wild-type (shmoos) ∆Fus3 ∆formin

43 Fig b CONCLUSION Mating factor G protein-coupled receptor GDP GTP Phosphory- lation cascade Shmoo projection forming Fus3 Formin P P P P Actin subunit Microfilament

44 The Specificity of Cell Signaling and Coordination of the Response Different kinds of cells have different collections of proteins These different proteins allow cells to detect and respond to different signals Even the same signal can have different effects in cells with different proteins and pathways Pathway branching and “cross-talk” further help the cell coordinate incoming signals Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

45 Fig a Signaling molecule Receptor Relay molecules Response 1 Cell A. Pathway leads to a single response. Cell B. Pathway branches, leading to two responses. Response 2 Response 3

46 Fig b Response 4Response 5 Activation or inhibition Cell C. Cross-talk occurs between two pathways. Cell D. Different receptor leads to a different response.

47 Signaling Efficiency: Scaffolding Proteins and Signaling Complexes Scaffolding proteins are large relay proteins to which other relay proteins are attached Scaffolding proteins can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

48 Fig Signaling molecule Receptor Scaffolding protein Plasma membrane Three different protein kinases

49 Signaling Efficiency: Scaffolding Proteins and Signaling Complexes Scaffolding proteins are large relay proteins to which other relay proteins are attached Scaffolding proteins can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

50 Fig Signaling molecule Receptor Scaffolding protein Plasma membrane Three different protein kinases

51 Concept 11.5: Apoptosis (programmed cell death) integrates multiple cell-signaling pathways Apoptosis is programmed or controlled cell suicide A cell is chopped and packaged into vesicles that are digested by scavenger cells Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

52 Fig µm

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

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

55 Apoptotic Pathways and the Signals That Trigger Them Caspases are the main proteases (enzymes that cut up proteins) that carry out apoptosis Apoptosis can be triggered by: – An extracellular death-signaling ligand – DNA damage in the nucleus – Protein misfolding in the endoplasmic reticulum Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

56

57 Jacobson et al (1997) Cell, Vol. 88, 347– 354, Apoptosis plays in an important role in normal developmental processes Studies on the development of the nervous system showed that in the process of assembling sensory fields, neurons are eliminated by orderly cell death in order to tailor sensory input to environmental stimuli (elimination or transplantation of limbs as key examples).

58 Programmed cell death during development. Programmed cell death is involved in forming structures such as the digits of the hand (a), deleting structures such as nearly all of an insect's larval components (b), controlling cell numbers in, for example, the nervous system (c) and eliminating abnormal cells such as those that harbour mutations (d).

59 Apoptosis is also important in the development of the nervous system

60 Apoptosis evolved early in animal evolution and is essential for the development and maintenance of all animals Apoptosis may be involved in some diseases (for example, Parkinson’s and Alzheimer’s); interference with apoptosis may contribute to some cancers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

61 Fig Interdigital tissue 1 mm

62

63 Fig. 11-UN1 Reception Transduction Response Receptor Relay molecules Signaling molecule Activation of cellular response 1 2 3

64 Question????

65 Chapter 12 The Cell Cycle

66 You should now be able to: 1.Describe the structural organization of the prokaryotic genome and the eukaryotic genome 2.List the phases of the cell cycle; describe the sequence of events during each phase 3.List the phases of mitosis and describe the events characteristic of each phase 4.Draw or describe the mitotic spindle, including centrosomes, kinetochore microtubules, nonkinetochore microtubules, and asters Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

67 5.Compare cytokinesis in animals and plants 6.Describe the process of binary fission in bacteria and explain how eukaryotic mitosis may have evolved from binary fission 7.Explain how the abnormal cell division of cancerous cells escapes normal cell cycle controls 8.Distinguish between benign, malignant, and metastatic tumors Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

68 Overview: The Key Roles of Cell Division The ability of organisms to reproduce best distinguishes living things from nonliving matter The continuity of life is based on the reproduction of cells, or cell division Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

69 Fig. 12-1

70 Fig. 12-2a 100 µm (a) Reproduction

71 Fig. 12-2b 200 µm (b) Growth and development

72 Fig. 12-2c 20 µm (c) Tissue renewal

73 Fig µmChromosomes Chromosome duplication (including DNA synthesis) Chromo- some arm Centromere Sister chromatids DNA molecules Separation of sister chromatids Centromere Sister chromatids

74 Phases of the Cell Cycle The cell cycle consists of – Mitotic (M) phase (mitosis and cytokinesis) – Interphase (cell growth and copying of chromosomes in preparation for cell division) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

75 Fig S (DNA synthesis) MITOTIC (M) PHASE Mitosis Cytokinesis G1G1 G2G2

76 Mitosis is conventionally divided into five phases: – Prophase – Prometaphase – Metaphase – Anaphase – Telophase Cytokinesis is well underway by late telophase BioFlix: Mitosis BioFlix: Mitosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

77 Prophase Fig. 12-6a Prometaphase G 2 of Interphase

78 Fig. 12-6b PrometaphaseProphase G 2 of Interphase Nonkinetochore microtubules Fragments of nuclear envelope Aster Centromere Early mitotic spindle Chromatin (duplicated) Centrosomes (with centriole pairs) Nucleolus Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule

79 Fig. 12-6c MetaphaseAnaphase Telophase and Cytokinesis

80 Fig. 12-6d MetaphaseAnaphase Telophase and Cytokinesis Cleavage furrow Nucleolus forming Metaphase plate Centrosome at one spindle pole Spindle Daughter chromosomes Nuclear envelope forming

81 Cleavage furrow Fig. 12-9a 100 µm Daughter cells (a) Cleavage of an animal cell (SEM) Contractile ring of microfilaments

82 Fig. 12-9b Daughter cells (b) Cell plate formation in a plant cell (TEM) Vesicles forming cell plate Wall of parent cell New cell wallCell plate 1 µm

83 Fig Chromatin condensing Metaphase AnaphaseTelophase Prometaphase Nucleus Prophase Nucleolus Chromosomes Cell plate 10 µm

84 Fig. 11-1


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