Use This Description to Answer the Following Question

question 81

Multiple Choice

Use this description to answer the following question.
A major group of G-protein-coupled receptors contains seven transmembrane α 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.
-Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because

• A) only target cells retain the appropriate DNA segments.
• B) intracellular receptors are present only in target cells.
• C) most cells lack the Y chromosome required.
• D) only target cells possess the cytosolic enzymes that transduce the testosterone.
• E) only in target cells is testosterone able to initiate a phosphorylation cascade.

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Definitions:

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