So the electron transport chain oxidizes the NADH molecules and uses that to generate ATP molecules. On the other hand, NADPH is actually used as a reducing agent in many different types of biological processes. What are these biological processes? Well, for instance, fatty acid biosynthesis, nucleotide biosynthesis, cholesterol, bisynthesis, neurotransmitter biosynthesis, as well as many different types of detoxification processes as we'll discuss in future lectures. Now, what's the difference between NADH and NADPH in terms of their structure? Well, the only difference is if we examine the second carbon hydroxyl group on one of the ribose units on the NADPH molecule it will be phosphorylated and in the case of NADH it is not phosphorylated.