BSCI 105 Lectures 20 & 21 Cell Communication

BSCI 105 Lectures 20 & 21 Cell Communication -...

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Overview: Cellular Messaging Cell-to-cell communication is essential for both multicellular and unicellular organisms Biologists have discovered some universal mechanisms of cellular regulation Cells most often communicate with each other via chemical signals For example, the fight-or-flight response is triggered by a signaling molecule called epinephrine
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External signals are converted to responses within the cell Microbes provide a glimpse of the role of cell signaling in the evolution of life
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Evolution of Cell Signaling The yeast, Saccharomyces cerevisiae , has two mating types, a and α Cells of different mating types locate each other via secreted factors specific to each type 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
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Exchange of mating factors Receptor α factor a factor Yeast cell, mating type a Yeast cell, mating type α Mating New a/ α cell 1 2 3 a a a/ α α α
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Pathway similarities suggest that ancestral signaling molecules evolved in prokaryotes and were modified later in eukaryotes The concentration of signaling molecules allows bacteria to sense local population density
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Individual rod-shaped cells Spore-forming structure (fruiting body) Aggregation in progress Fruiting bodies 1 2 3 0.5 mm 2.5 mm
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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
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Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells (a) Cell junctions (b) Cell-cell recognition
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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 The ability of a cell to respond to a signal depends on whether or not it has a receptor specific to that signal
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Local signaling Long-distance signaling Target cell Secreting cell Secretory vesicle Local regulator diffuses through extracellular fluid. (a) Paracrine signaling (b) Synaptic signaling Electrical signal along nerve cell triggers release of neurotransmitter. Neurotransmitter diffuses across synapse. Target cell is stimulated. Endocrine cell Blood vessel Hormone travels in bloodstream. Target cell specifically binds hormone. (c) Endocrine (hormonal) signaling
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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
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EXTRACELLULAR FLUID CYTOPLASM Reception Transduction
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This note was uploaded on 01/29/2012 for the course BSCI 105 taught by Professor Jensen during the Fall '07 term at Maryland.

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BSCI 105 Lectures 20 & 21 Cell Communication -...

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