In order to detect a signal (that is, to be a target cell), a neighbor cell must have the right receptor for that signal. When a signaling molecule binds to its receptor, it alters the shape or activity of the receptor, triggering a change inside of the cell. Signaling molecules are often called ligands, a general term for molecules that bind specifically to other molecules (such as receptors).
A chunk paragraph is just a way of developing your skill in writing - it is a style or format which forces you to explain your ideas and arguments. Here's you do chunk writing: Write your topic sentence.
Based off of De Groot's chess experiment, Chase and Simon (1973) began to clear up what is called the chunking theory, which has pretty much been the basis of expertise. A pretty, straightforward definition centers the idea of a chunk around long-term memory (LTM).