Campbell Biology Chapter 11 Outline

Topics: Signal transduction, Cell signaling, Hormone Pages: 5 (1160 words) Published: December 21, 2012
Chapter 11: Cell Communication
Concept 11.1 External signals are converted to responses within the cell. I. Evolution of Cell Signaling
1. signal transduction pathway. a specific cellular response in a series of steps
2. signaling mechanisms first evolved in ancient prokaryotes and unicellular eukaryotes, then adopted for new uses
3. quorum sensing. allows bacterial populations to coordinate behaviors to carry out activities only productive when performed by a given number of cells in synchrony
4. biofilm. an aggregation of bacterial cells adhered to a surface (generally derive nutrients from surface - cavities) II. Local and Long-Distance Signaling
1. cells in a multicellular organisms usually communicate via chemical messengers targeted for cells that may be adjacent
2. animals cells may communicate via direct contact b/w membrane-bound surface molecules in cell-cell recognition
a. important in embryonic development and the immune response
3. local regulators. messenger molecules secreted by signaling cell that only influences cells in the vicinity
a. growth factors. compounds that stimulate nearby target cells to grow and divide
b. paracrine signaling. when numerous cells respond to growth factor produced by one cell
4. synaptic signaling. occurs in animal nervous system in which an electrical signal triggers the secretion of neurotransmitters
5. hormones are used for long-distance signaling, which travel via the circulatory system
6. plant hormones more often diffuse through the cells or through the air as a gas III. The Three Stages of Cell Signaling: A Preview
1. Reception. the target cell's detection of a signaling molecule coming from outside the cell
a. detected when the signaling molecules binds to a receptor protein located at the cell's surface/interior
2. Transduction. converts the signal to a form that can bring about a specific cellular response
3. Response. may be almost any cellular activity (catalysis, rearrangement of cytoskeleton, activation of certain genes) Concept 11.2: Reception: A signaling molecules binds to a receptor protein, causing it to change shape. I. Receptors in the Plasma Membrane

1. transmembrane receptor binds to specific sites and transmits info from outside to inside the cell by changing shape
2. three major types: G protein-coupled receptors, receptor tyrosine kinases, ligand-gated ion channel receptors
3. abnormal functioning of receptor tyrosine kinases is associated with many types of cancer II. Intracellular Receptors
1. found in either the cytoplasm or the nucleus of target cells
2. transcription factor. proteins that control which genes are turned on and transcribed into mRNA Concept 11.3: Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell. I. Signal Transduction Pathways

1. the binding of a specific signaling molecule to a receptor triggers the first step in the chain of molecular interactions II. Protein Phosphorylation and Dephosphorylation
1. these two are major widespread cellular mechanisms for regulating protein activity
2. protein kinase. enzyme that transfers phosphate groups from ATP to a protein
3. many of the relay molecules in signal transduction pathways are protein kinases that often act on other protein kinases
4. protein phosphatases. enzymes that can rapidly remove phosphate groups from proteins (dephosphorylation) III. Small Molecules and Ions as Second Messengers
1. second messengers. small, non-protein, water-soluble molecules/ions that easily diffuse throughout the cell
2. most widely used second messengers are cyclic AMP and Calcium ions
3. Cyclic AMP
a. the binding of epinephrine to membrane of liver cell elevates the cytosolic concentration of cAMP
b. membrane enzyme called adenylyl cyclase converts ATP to cAMP
c. cAMP activates the serine/threonine kinase called protein kinase A
d. cholera toxin causes G protein...
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