Chapter 11 - Cell Communication

Chapter 11 - Cell Communication - Chapter 11 Independent...

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Chapter 11 Independent Notes – Cell Communication – Page 1 Max Sauberman AP Biology – Mr. Schilp Chapter 11 Cell Communication Evolution of Cell Signaling: Yeast ( Saccharomyces cerevisiae ) mating behavior is coordinated by chemical signaling. Yeast cells identify their mates by chemical signaling. There are two sexes, or mating types: a or α. Type-a cells secrete an a-factor chemical signal, which can bind to specific receptor proteins on α cells. Type- α cells secrete α-factor signals, binding to receptors on a cells. These two factors cause the cells to grow toward each other; the result is the fusion of two opposite cells. The new a/α cell contains all the genes of both original cells. Signal Transduction Pathways: The mating signal at the cell surface transduced into a form that brings about the cellular response of mating. The process by which a signal on a cell’s surface is converted into a specific cellular response is a series of steps called a signal transduction pathway. Signal transduction is similar in yeast and mammals, and bacteria and plants. These similarities suggest that early versions of cell-signaling mechanisms evolved before multicellular organisms appeared on earth. Signaling via Direct Contact: Cells may communicate by direct contact, through cell junctions that directly connect the cytoplasms of adjacent cells, so signaling substances in the cytosol can pass freely between adjacent cells. Animal cells can communicate via direct contact between membrane-bound surface molecules. This signaling, called cell-cell recognition is important in embryonic development and immune response. Local Regulators: In other cases, messenger molecules are secreted by the signaling cell. A chemical signal that communicates between two nearby cells is a local regulator. In animals, growth factors are local regulator compounds that stimulate nearby target cells to grow/multiply. Numerous cells can receive and respond to a growth factor in the vicinity, called paracrine signaling.
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Chapter 11 Independent Notes – Cell Communication – Page 2 Synaptic signaling occurs in the animal nervous system, where an electrical signal along a nerve cell triggers the secretion of a chemical signal in neurotransmitters, which diffuses across the synapse (the space between the nerve cell and its target cell), stimulating the target. Plants must use mechanisms different from those operating locally in animals, because of their cell walls. Hormones: A chemical signal that communicates between cells some distance apart is called a hormone. In hormonal signaling in animals (endocrine signaling), specialized cells release hormones into vessels, which they use to travel to target cells across the body. Plant hormones (called growth regulators) travel in vessels but more often reach their targets by moving through
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This note was uploaded on 03/17/2011 for the course BIO 101 taught by Professor Sullivan during the Spring '08 term at Harvard.

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Chapter 11 - Cell Communication - Chapter 11 Independent...

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