Figure 11.0 Yeast

Figure 11.1 Communication between mating yeast cells

Cell Communication

•Between separate organisms

•Between cells within an organism

Figure 11.2 Communication among bacteria

Figure 11.3 Local and long-distance cell communication in animals

Communicating cells can be close together or far apart.

Paracrine Signaling

•Histamine released by mast cells.

•Inflammation of nearby tissue

•Increased secretion of stomach acid

Figure 11.4 Communication by direct contact between cells

Three Stages of Cell Signaling1. Reception: detection of signal2. Transduction: signal converted to form

that yields cellular response3. Response

Earl Sutherland

Figure 11.5 Overview of cell signaling (Layer 1)

Figure 11.5 Overview of cell signaling (Layer 2)

Figure 11.5 Overview of cell signaling (Layer 3)

Signal Reception• Receptors

– Membrane protein– On surface of cell– Specific– Ligand binds receptor causing a change in

conformation– Signal transduction pathway initiated

• Types of membrane receptors– G-Protein Linked Receptors– Tyrosine kinase receptors– Ion-channel receptors

Figure 11.6 The structure of a G-protein-linked receptor

Figure 11.7 The functioning of a G-protein-linked receptor

Figure 11.8 The structure and function of a tyrosine-kinase receptor

Figure 11.9 A ligand-gated ion-channel receptor

Figure 11.10 Steroid hormone interacting with an intracellular receptor

Signal Transduction Pathways• Process of relaying signal to produce

response.• Often several steps/processes• Amplification• Involves second messengers

– Cyclic AMP (cAMP), Ca2+

• Protein Kinase: Enzyme that transfers phosphate from ATP to a protein

• Protein Phosphatase: enzyme that removes phosphate from a protein.

Figure 11.11 A phosphorylation cascade

Figure 11.12 Cyclic AMP

Figure 11.13 cAMP as a second messenger

Examples of Hormone-induced Cellular Responses Mediated by cAMP

Target Tissue Hormone Major Response

Thyroid gland TSH TH synthesis/secretion

Muscle Adrenaline Glycogen breakdown

Heart Adrenaline Increase heart rate/force of contract

Liver Glucagon Glycogen breakdown

Figure 11.14 The maintenance of calcium ion concentrations in an animal cell

Figure 11.15 Calcium and inositol triphosphate in signaling pathways (Layer 1)

Figure 11.15 Calcium and inositol triphosphate in signaling pathways (Layer 2)

Figure 11.15 Calcium and inositol triphosphate in signaling pathways (Layer 3)

Some Cellular Responses Mediated by G-Protein-linked Receptors Coupled to Inositol Phospholipid Signaling

Pathway

Target Tissue Signaling Molecule

Major Response

Liver Vasopressin Glycogen breakdown

Pancreas Acetylcholine Amylase secretion

Smooth Muscle Acetylcholine Contraction

Mast cells Antigen Histamine secretion

Figure 11.16 Cytoplasmic response to a signal: the stimulation of glycogen breakdown by epinephrine

Figure 11.17 Nuclear response to a signal: the activation of a specific gene by a growth factor

Amplification of Signal Response

Figure 11.18 The specificity of cell signaling

Figure 11.19 A scaffolding protein