Which of the following would be considered a cell-surface receptor?

• A. Ribosome
• B. G protein-coupled receptor (GPCR)
• C. Mitochondrial matrix protein
• D. DNA polymerase

Answer: (B)

Verified step by step guidance

1. Understand the definition of a cell-surface receptor: A cell-surface receptor is a protein located on the plasma membrane that binds to extracellular signaling molecules (ligands) and transmits signals into the cell.
2. Analyze the options provided: Ribosome, G protein-coupled receptor (GPCR), Mitochondrial matrix protein, and DNA polymerase.
3. Eliminate options that do not fit the definition of a cell-surface receptor: Ribosomes are involved in protein synthesis, not signaling. Mitochondrial matrix proteins are located inside mitochondria, not on the cell surface. DNA polymerase is an enzyme involved in DNA replication, not signal transduction.
4. Focus on the G protein-coupled receptor (GPCR): GPCRs are well-known cell-surface receptors that play a key role in signal transduction by binding to extracellular ligands and activating intracellular signaling pathways.
5. Conclude that the correct answer is G protein-coupled receptor (GPCR), as it matches the definition of a cell-surface receptor.