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.
A chunk is a unit of information in short-term memory â a string of letters, a word, or a series or numbers. By chunking information into small bits we seek to accommodate the limits of our short-term memory. The goal of chunking is to aid processing of information.