For BI320, there is one recommended (not required) textbook. It is:
Becker's World of the Cell 9E by Hardin, Jeff
Edition: 9th ISBN: 9780321934925
Format: Hardcover Publisher: PEARSON
Pub. Date: 12/11/2015
You can buy a used copy or rent a copy of this book - I don't care if it is a hardcover, loose leaf, or eTextbook (hardcover ISBN listed). If you want a cheaper option, the 8th edition of this book is pretty good too (I like the examples and experimental methods described in the 9th edition better).