In the context of membrane-bound receptors and second messenger systems, hormone therapy that reduces the interaction of hormones with their target cells most directly decreases hormone binding to which structure?

• A. Gap junctions between adjacent cells
• B. Mitochondrial inner membrane transport proteins
• C. Plasma membrane receptors on target cells
• D. Ribosomes in the cytosol

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the role of membrane-bound receptors in hormone signaling. These receptors are proteins located on the plasma membrane of target cells that specifically bind hormones, initiating a cellular response.
2. Step 2: Recognize that second messenger systems are activated when a hormone binds to its plasma membrane receptor, triggering intracellular signaling cascades without the hormone entering the cell.
3. Step 3: Identify that hormone therapy aimed at reducing hormone interaction with target cells would most directly affect the initial binding step, which occurs at the plasma membrane receptors.
4. Step 4: Differentiate plasma membrane receptors from other cellular structures such as gap junctions, mitochondrial transport proteins, and ribosomes, which do not directly mediate hormone binding in this context.
5. Step 5: Conclude that the structure whose hormone binding is most directly decreased by such hormone therapy is the plasma membrane receptors on target cells.