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Enzyme-linked receptors have a membrane-spanning region built from a single structural element. What is that element?
ASeven separate transmembrane helices in a row
BA beta-pleated sheet that forms a pore
CA ring of six identical protein subunits
DA single alpha-helical region of the peptide strand
Answer & Solution
Correct answer: D. A single alpha-helical region of the peptide strand
1. Enzyme-linked receptors normally have large extracellular and intracellular domains.
2. Their membrane-spanning region, however, consists of only a single alpha-helical region of the peptide strand.
3. Seven transmembrane helices instead describe G-protein-linked receptors, a different receptor category.
4. A beta-pleated sheet forming a pore is not the structure described for the membrane-spanning region of enzyme-linked receptors.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 9 "Cell Communication", section 9.1 Signaling Molecules and Cellular Receptors_
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