Question

multiple choice 1 point
which illustration is showing a ligand binding to a receptor?

Explanation:

Ligand - receptor binding involves a specific molecule (ligand) fitting into a complementary site on a receptor protein. In option D, there is a clear depiction of a ligand (green structure) binding to a receptor (purple structure), which matches the concept of ligand - receptor interaction. Option A shows transport (possibly facilitated diffusion or active transport with ATP involvement), option B seems to show a channel - like structure (maybe a channel protein in operation), and option C shows two separate entities (not a binding event).

Answer:

D.