Cell surface receptors — Which set correctly belongs to the category of plasma membrane receptors?
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AEnzyme linked receptors
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BIon-channel linked receptors
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CG protein linked receptors
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DAll of these
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ENuclear (intracellular) receptors
Answer
Correct Answer: All of these
Explanation
Introduction:Cells deploy multiple classes of receptors at the plasma membrane to detect and transduce extracellular signals. This question reviews which families are considered cell surface receptors.
Given Data / Assumptions:
- Receptors can be located at the cell surface or inside the cell.
- Each listed class has characteristic mechanisms of action.
- We are categorizing by location (surface) rather than ligand type.
Concept / Approach:Enzyme linked receptors (e.g., receptor tyrosine kinases), ion channel linked receptors (ligand gated channels), and G protein coupled receptors are all embedded in the plasma membrane and initiate signaling upon ligand binding.
Step-by-Step Solution:
1) Enzyme linked: transmembrane proteins with intracellular catalytic domains.2) Ion channel linked: ligand binding opens or closes an ion pore across the membrane.3) GPCRs: seven transmembrane helices that activate heterotrimeric G proteins.4) Because all three are cell surface located, the comprehensive answer is 'All of these'.Verification / Alternative check:Biochemistry texts consistently group these three under cell surface receptor classes, in contrast to intracellular nuclear receptors that bind lipophilic ligands.
Why Other Options Are Wrong:
- Any single class alone is incomplete given the question asks which come under the category.
- Nuclear receptors: intracellular, not cell surface.
Common Pitfalls:Mixing location categories with signaling mechanism categories. Here, location at the plasma membrane defines cell surface receptors.
Final Answer:All of these.