Final answer:
Internal receptors are located in the cytoplasm of the cell and respond to hydrophobic ligands, while cell-surface receptors are membrane-anchored proteins that bind to external ligand molecules. Internal receptors interact directly with the cell's DNA and promote the initiation of transcription, while cell-surface receptors convert extracellular signals into intracellular signals through signal transduction.
Step-by-step explanation:
Internal receptors, also known as intracellular or cytoplasmic receptors, are located in the cytoplasm of the cell and respond to hydrophobic ligands that can cross the plasma membrane. These receptors bind to ligand molecules that cross the plasma membrane and form a ligand-receptor complex. The complex then moves to the nucleus and interacts directly with cellular DNA, promoting the initiation of transcription. Cell-surface receptors, on the other hand, are membrane-anchored proteins that bind to external ligand molecules and perform signal transduction, converting the extracellular signal into an intracellular signal.