Which of the following is a receptor molecule involved in cell signaling?

• A. Adenosine triphosphate (ATP)
• B. Ribosomal RNA (rRNA)
• C. G protein-coupled receptor (GPCR)
• D. Actin filament

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of cell signaling. Cell signaling is the process by which cells communicate with each other using signaling molecules and receptor proteins. Receptor molecules are specialized proteins that bind to signaling molecules and initiate a cellular response.
2. Step 2: Review the function of each option provided. Adenosine triphosphate (ATP) is a molecule that stores and transfers energy within cells, not a receptor. Ribosomal RNA (rRNA) is involved in protein synthesis, not cell signaling. Actin filaments are part of the cytoskeleton and provide structural support, not a receptor.
3. Step 3: Learn about G protein-coupled receptors (GPCRs). GPCRs are a large family of receptor proteins located on the cell membrane. They play a key role in cell signaling by binding to signaling molecules (ligands) and activating intracellular signaling pathways.
4. Step 4: Recognize that GPCRs are specifically designed to detect extracellular signals and transmit them into the cell, making them a receptor molecule involved in cell signaling.
5. Step 5: Conclude that the correct answer is G protein-coupled receptor (GPCR), as it is the only option that functions as a receptor molecule in cell signaling.