(D)an atom can join with other kinds of atoms.
Basically he explained what a molecule is.
Find the attachment for the answer.
Note: I have added the complete question in the attachment.
Can you please show the answer choices to pick from?
Answer:
Cells in a large multicellular organism communicate with each other by chemical signals. These signals are passed from one cell to another. To receive and respond to a chemical signal, a cell must have a <u><em>receptor</em></u> for that chemical.
Explanation:
To generate a physiological response, all cells in the body have special proteins called receptors. These receptors are involved in detecting a chemical signal and generating a response. The receptors are specific for different kind of chemical signals. For example, a dopamine receptor will bind a dopamine molecule whereas an insulin receptor will be able to bind an insulin molecule. Apart from chemical signals, some cells might also respond to mechanical signals.
