Cell Communication Review

Gap junctions between animal cells Plasmodesmata between plant cells Figure 11.4 Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells (a) Cell junctions Figure 11.4 Communication by direct contact between cells. (b) Cell-cell recognition

Neurotransmitter diffuses across synapse. Secreting cell Figure 11.5a Local signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter. Neurotransmitter diffuses across synapse. Secreting cell Secretory vesicle Figure 11.5 Local and long-distance cell signaling by secreted molecules in animals. Local regulator diffuses through extracellular fluid. Target cell is stimulated. (a) Paracrine signaling (b) Synaptic signaling

Long-distance signaling Figure 11.5b Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream. Target cell specifically binds hormone. Figure 11.5 Local and long-distance cell signaling by secreted molecules in animals. (c) Endocrine (hormonal) signaling

EXTRACELLULAR FLUID CYTOPLASM Plasma membrane 1 Reception Receptor Figure 11.6-1 EXTRACELLULAR FLUID CYTOPLASM Plasma membrane 1 Reception Receptor Figure 11.6 Overview of cell signaling. Signaling molecule

Relay molecules in a signal transduction pathway Figure 11.6-2 EXTRACELLULAR FLUID CYTOPLASM Plasma membrane 1 Reception 2 Transduction Receptor Relay molecules in a signal transduction pathway Figure 11.6 Overview of cell signaling. Signaling molecule

Relay molecules in a signal transduction pathway Figure 11.6-3 EXTRACELLULAR FLUID CYTOPLASM Plasma membrane 1 Reception 2 Transduction 3 Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Figure 11.6 Overview of cell signaling. Signaling molecule

Signaling molecule binding site Figure 11.7a Signaling molecule binding site Segment that interacts with G proteins Figure 11.7 Exploring: Cell-Surface Transmembrane Receptors G protein-coupled receptor

G protein-coupled receptor Plasma membrane Activated receptor Figure 11.7b G protein-coupled receptor Plasma membrane Activated receptor Signaling molecule Inactive enzyme GTP GDP GDP CYTOPLASM G protein (inactive) Enzyme GTP 1 2 GDP Activated enzyme Figure 11.7 Exploring: Cell-Surface Transmembrane Receptors GTP GDP P i 3 Cellular response 4

Signaling molecule (ligand) Ligand-binding site Figure 11.7c Signaling molecule (ligand) Ligand-binding site  helix in the membrane Signaling molecule Tyr Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr CYTOPLASM Receptor tyrosine kinase proteins (inactive monomers) Dimer 1 2 Activated relay proteins Cellular response 1 Figure 11.7 Exploring: Cell-Surface Transmembrane Receptors Tyr Tyr P Tyr Tyr P Tyr Tyr P P Tyr Tyr P Tyr P Tyr Tyr Tyr P P Cellular response 2 Tyr Tyr P Tyr Tyr P Tyr Tyr P 6 ATP 6 ADP P Activated tyrosine kinase regions (unphosphorylated dimer) Fully activated receptor tyrosine kinase (phosphorylated dimer) Inactive relay proteins 3 4

Signaling molecule (ligand) Figure 11.7d 1 2 3 Gate closed Ions Gate open Gate closed Signaling molecule (ligand) Plasma membrane Ligand-gated ion channel receptor Cellular response Figure 11.7 Exploring: Cell-Surface Transmembrane Receptors

Hormone (testosterone) EXTRACELLULAR FLUID Figure 11.9-1 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein DNA Figure 11.9 Steroid hormone interacting with an intracellular receptor. NUCLEUS CYTOPLASM

Hormone (testosterone) EXTRACELLULAR FLUID Figure 11.9-2 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.9 Steroid hormone interacting with an intracellular receptor. NUCLEUS CYTOPLASM

Hormone (testosterone) EXTRACELLULAR FLUID Figure 11.9-3 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.9 Steroid hormone interacting with an intracellular receptor. NUCLEUS CYTOPLASM

Hormone (testosterone) EXTRACELLULAR FLUID Figure 11.9-4 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.9 Steroid hormone interacting with an intracellular receptor. mRNA NUCLEUS CYTOPLASM

Hormone (testosterone) EXTRACELLULAR FLUID Figure 11.9-5 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.9 Steroid hormone interacting with an intracellular receptor. mRNA NUCLEUS New protein CYTOPLASM

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

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

First messenger (signaling molecule such as epinephrine) Figure 11.12 First messenger (signaling molecule such as epinephrine) Adenylyl cyclase G protein G protein-coupled receptor GTP ATP Second messenger cAMP Figure 11.12 cAMP as a second messenger in a G protein signaling pathway. Protein kinase A Cellular responses

Inactive transcription factor Active transcription factor Figure 11.15 Growth factor Reception Receptor Phosphorylation cascade Transduction CYTOPLASM Inactive transcription factor Active transcription factor Figure 11.15 Nuclear responses to a signal: the activation of a specific gene by a growth factor. Response P DNA Gene NUCLEUS mRNA

Glucose 1-phosphate (108 molecules) Figure 11.16 Reception Binding of epinephrine to G protein-coupled receptor (1 molecule) Transduction Inactive G protein Active G protein (102 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (102) ATP Cyclic AMP (104) Inactive protein kinase A Active protein kinase A (104) Figure 11.16 Cytoplasmic response to a signal: the stimulation of glycogen breakdown by epinephrine. Inactive phosphorylase kinase Active phosphorylase kinase (105) Inactive glycogen phosphorylase Active glycogen phosphorylase (106) Response Glycogen Glucose 1-phosphate (108 molecules)

Signal Transduction Which of the following best describes a signal transduction pathway? binding of a signal molecule to a cell protein catalysis mediated by an enzyme sequence of changes in a series of molecules resulting in a response binding of a ligand on one side of a membrane that results in a change on the other side Answer: c

Steroid Receptors A steroid hormone binds to an intracellular receptor Steroid Receptors A steroid hormone binds to an intracellular receptor. When it does, the resulting complex is able to do which of the following? Why? open channels in the membrane for other substances to enter open channels in the nuclear envelope for cytoplasmic molecules to enter mediate the transfer of phosphate groups to/from ATP act as a transcription factor in the nucleus Answer: d

Phosphorylation In reactions mediated by protein kinases, what does phosphorylation of successive proteins do to drive the reaction? make functional ATP change a protein from its inactive to its active form change a protein from its active to its inactive form produce an increase in the cell’s store of inorganic phosphates Answer: b Note: some responses would be true if the question were not specifically about driving a reaction.

Signal Amplification Which of the following is an example of signal amplification? activation of 100 molecules by a single signal binding event activation of a specific gene by a growth factor activation of an enzyme molecule utilization of a second messenger system Answer: b