Final answer:
The statement is true; cells react to the binding of a molecule to a receptor protein by changing the shape of the protein, which initiates a signaling cascade leading to various cellular responses.
Step-by-step explanation:
The statement that a cell responds to the binding of a molecule with a receptor protein when the protein changes shape is true. Cells have protein receptors on their surfaces, which undergo conformational changes upon the binding of a ligand - a molecule that specifically interacts with the receptor. This binding initiates a cascade of intracellular events that can lead to various cellular responses, such as changes in gene expression and subsequent protein production.Receptor proteins are highly specific, only binding to particular ligands. Nonpolar ligands generally diffuse across the cell membrane to bind with internal receptors, while polar ligands interact with cell-surface receptors. An example of this is the interaction with a G-protein when a hormone binds to a cell-surface receptor, which then triggers a series of signaling pathways within the cell.