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Homework _14, with answers 02_13_09

Homework _14, with answers 02_13_09 - Where is the carboxyl...

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Homework #14, 02/13/09 1. Which of the following are chemical messengers that pass through the plasma membrane of cells and have receptor molecules in the cytoplasm? A. Insulin B. Testosterone C. G-protein D. Cholesterol E. EGF (Ans B) 2. Testosterone functions inside a cell by A. Acting as a signal receptor that activates ion-channel proteins B. Acting as a steroid signal receptor that activates ion-channel receptors C. Becoming a second messenger that inhibits adenyl cyclase D. Binding with a receptor protein that enters the nucleus and activates specific genes E. Coordinating a phosphorylation cascade that increases glycogen metablolism (Ans D) 3. A major group of G protein-linked receptors contain seven transmembrane alpha helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.
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Unformatted text preview: Where is the carboxyl end found? A. At the exterior of the cell membrane B. Connected with loops 5 and 6 C. At the interior of the cell membrane D. Embedded in the bilayer E. Connected to the extracellular loops 1 and 2 (Ans C) 4. In general, a signal transmitted via phosphorylation of a series of proteins A. Brings a conformational change to each protein B. Requires binding of a hormone to a cytosol receptor C. Cannot occur in yeasts because they lack protein phosphatases D. Requires phosphorylase activity E. Allows target cells to change their shape and therefore their activity (Ans A) 5. Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins? A. G-protein-linked receptor signaling B. Ligand-gated ion channel signaling C. Adenylyl cyclase activity D. Phosphatase activity E. Receptor tyrosine kinase activity (Ans E)...
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