How do I cite a quote in a college application essay?

In one of the essays I'm using to apply to college I use a quote from the book The Fountainhead by Ayn Rand. I'm not sure to what extent I should cite this quote if at all. I begin the essay with the quote and then spend the rest of the essay talking about the book. I never exactly specify in writing that the quote came from the book, but it should be obvious. Is it fine as it is, or should I use MLA format and put quotations at the end, i.e. (Rand pg#)? Should I even go so far as to cite the book at the end of the essay, which seems a bit too formal for a quick essay?