Which statement describes the difference between intracellular and membrane receptors?

Which statement describes the difference between intracellular and membrane receptors?

• A. An intracellular receptor cannot bind ligand.
• B. A membrane receptor binds DNA directly to regulate transcription.
• C. An intracellular receptor binds a ligand and can bind DNA; a membrane receptor cannot.
• D. A membrane receptor is located in the cytosol and never associated with membranes.

Answer: (C)

Localization and mechanism of signaling differentiate intracellular and membrane receptors. Intracellular receptors reside inside the cell (in the cytosol or nucleus) and bind ligands that can cross the cell membrane, such as steroid hormones. After binding, they often act directly as transcription factors and can bind to DNA to regulate gene expression. That direct DNA-binding capability is a hallmark of many intracellular receptors. Membrane receptors, by contrast, sit in the plasma membrane. They bind their ligands outside the cell and initiate signaling cascades inside the cell, typically through second messengers or phosphorylation events, which then influence cellular responses. They do not usually bind DNA directly themselves; transcriptional changes arise from downstream signaling rather than direct DNA interaction. So the statement that fits best is that an intracellular receptor binds a ligand and can bind DNA, whereas a membrane receptor cannot. The other options are inconsistent with this fundamental distinction: intracellular receptors do bind ligands, membrane receptors do not bind DNA directly, and membrane receptors are defined by their membrane localization, not by being free in the cytosol.

Localization and mechanism of signaling differentiate intracellular and membrane receptors. Intracellular receptors reside inside the cell (in the cytosol or nucleus) and bind ligands that can cross the cell membrane, such as steroid hormones. After binding, they often act directly as transcription factors and can bind to DNA to regulate gene expression. That direct DNA-binding capability is a hallmark of many intracellular receptors.

Membrane receptors, by contrast, sit in the plasma membrane. They bind their ligands outside the cell and initiate signaling cascades inside the cell, typically through second messengers or phosphorylation events, which then influence cellular responses. They do not usually bind DNA directly themselves; transcriptional changes arise from downstream signaling rather than direct DNA interaction.

So the statement that fits best is that an intracellular receptor binds a ligand and can bind DNA, whereas a membrane receptor cannot. The other options are inconsistent with this fundamental distinction: intracellular receptors do bind ligands, membrane receptors do not bind DNA directly, and membrane receptors are defined by their membrane localization, not by being free in the cytosol.