AP Biology Activities - Ch. 11 & 12

AP Biology Activities - Ch. 11 & 12 - Additional...

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Additional Activities Chapter 11 Activity: Overview of Cell Signaling Cells communicate with one another by means of chemical signals. To signal this cell, click on the signal molecule outside the cell that fits the receptor. For the receiving cell, there are three stages in the signaling process: reception, transduction, and cell response. The cell targeted by a particular signal has a receptor molecule complementary to the signal molecule, or ligand. The ligand fits like a key in a lock and triggers a change in the receptor molecule. Signal transduction converts the change in the receptor to a form that can bring about a cellular response. This might involve a series of steps— a signal transduction pathway— that alters and amplifies the change. In the third stage of cell signaling, the transduction process brings about a cellular response. This can be any of many different cellular activities, such as activation of a certain enzyme, rearrangement of the cytoskeleton, or activation of specific genes. Activity: Reception Many signal molecules, such as neurotransmitters, act through G-protein-linked receptors. This kind of receptor spans the cell membrane and works through a protein called a G protein. When the signal molecule binds to the receptor, the receptor becomes activated. It is now able to activate a specific G protein by causing GTP to displace GDP on the G protein. The activated G protein then binds to another protein, usually an enzyme, and alters its activity. Growth factors signal cells to grow and divide by acting though receptor tyrosine kinases. Binding of signal molecules causes two polypeptides to join, activating parts of each that act as tyrosine-kinase enzymes, which then phosphorylate tyrosines in the tail of the other polypeptide. The receptor protein is now recognized by specific relay proteins inside the cell. Some membrane receptors are ligand-gated ion channels. They are protein pores in the plasma membrane that allow or block the passage of certain ions through the membrane. This changes the shape of the protein, opening a channel through the membrane. Ions flow through the channel, and the change in ion concentration triggers a cellular response. Intracellular receptors are proteins located inside the target cell. Nonpolar molecules like steroids and thyroid hormones are able to pass through the plasma membrane and bind to a receptor protein in the cytoplasm or nucleus of a target cell. The activated receptor triggers a change in the cell. Steroids cause receptors to turn genes on and off.
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Activity: Signal Transduction Pathways Receptors that are plasma-membrane proteins usually affect the cell through multistep signal transduction pathways. These pathways allow for amplification of signals and signal coordination and regulation. Signal
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This note was uploaded on 10/01/2011 for the course BIOLOGY 1510 taught by Professor --- during the Spring '11 term at Georgia State University, Atlanta.

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AP Biology Activities - Ch. 11 & 12 - Additional...

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