Chapter 11 Cell Communication 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 Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Fig. 11-1
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
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 Signal transduction pathways convert signals on a cell s surface into cellular responses Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-2 Receptor factor 1 Exchange of mating factors a Yeast cell, mating type a a factor Yeast cell, mating type 2 Mating a 3 New a/ cell a/
Pathway similarities suggest that ancestral signaling molecules evolved in prokaryotes and were modified later in eukaryotes The concentration of signaling molecules allows bacteria to detect population density Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-3 1 Individual rodshaped cells 0.5 mm 2 Aggregation in process 3 Spore-forming structure (fruiting body) Fruiting bodies
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 Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-4 Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells (a) Cell junctions (b) Cell-cell recognition
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 Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-5 Local signaling Long-distance signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter Endocrine cell Blood vessel Secreting cell Secretory vesicle Neurotransmitter diffuses across synapse Hormone travels in bloodstream to target cells Local regulator diffuses through extracellular fluid (a) Paracrine signaling Target cell is stimulated (b) Synaptic signaling Target cell (c) Hormonal signaling
Fig. 11-5ab Local signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter Secreting cell Secretory vesicle Neurotransmitter diffuses across synapse Local regulator diffuses through extracellular fluid (a) Paracrine signaling Target cell is stimulated (b) Synaptic signaling
Fig. 11-5c Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling
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 Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-6-1 EXTRACELLULAR FLUID Plasma membrane CYTOPLASM 1 Reception Receptor Signaling molecule
Fig. 11-6-2 EXTRACELLULAR FLUID Plasma membrane CYTOPLASM 1 Reception 2 Transduction Receptor Relay molecules in a signal transduction pathway Signaling molecule
Fig. 11-6-3 EXTRACELLULAR FLUID Plasma membrane CYTOPLASM 1 Reception 2 Transduction 3 Response Receptor Relay molecules in a signal transduction pathway Activation of cellular response Signaling molecule
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
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
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
Fig. 11-7a Signaling-molecule binding site Segment that interacts with G proteins G protein-coupled receptor
Fig. 11-7b G protein-coupled receptor Plasma membrane Activated receptor Signaling molecule Inactive enzyme GDP CYTOPLASM G protein (inactive) Enzyme GDP GTP 1 2 Activated enzyme GTP GDP P i Cellular response 3 4
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
Fig. 11-7c Signaling molecule (ligand) Helix Ligand-binding site Signaling molecule osines CYTOPLASM Receptor tyrosine kinase proteins Dimer 1 2 Activated relay proteins 6 ATP 6 ADP P P P P P P P P P P P P Cellular response 1 Cellular response 2 Activated tyrosine kinase regions Fully activated receptor tyrosine kinase Inactive relay proteins 3 4
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
Fig. 11-7d 1 Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane 2 Gate open Cellular response 3 Gate closed
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