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.
Body Paragraphs. A body paragraph is a group of related sentences about a particular topic or idea directly relating to the thesis. Because essays are composed of multiple body paragraphs, writing and organizing good paragraphs is one of the most important aspects of creating a well-organized and developed essay. The term body paragraph refers to any paragraph that follows the introduction and comes before the conclusion. The majority of any essay consists of multiple body paragraphs, and it is in these paragraphs where the main information is presented.