The life of a science officer is not easy. Most often, they are stuck with duties like OPS (yes, Data was a science officer) until something comes along that requires analysis. In space, nothing conforms to any set definition - a lifeform may be discovered that does not adhere to the definition of life, but it is most obviously living.
It is important that you have a general understanding of all the terms and concepts presented in this class, as your commanding officer will want to know exactly what it is that your ship has encountered. If you're not sure, don't pretend you know, as this will only lead to problems later. Speculate! Say, "My hypothesis is . . ." or "It's too early to gain a definitive answer, but I believe that . . ."
Launch probes to gather interstellar data. Work with the medical department to gather information about horrible infections. Use the laboratories on board to analyze different kinds of goo. Delegate - always delegate! A science officer, in a crisis situation, cannot handle everything at once, which is why there are junior officers to assist you.
When it comes to RPGing, don't be afraid to make conclusions. Don't wait for the GM to tell you what it is you've found, say what it is. At the worst, the GM will issue a nullified post order. It's never a crime to be too creative, but being under-creative is what keeps people at the sci-5 position.
Don't rely on the concepts of this class as your only source of scientific information. This is just a basic-level class; it's a lot like a liberal arts science class - we cover a lot of subject matter, but depth is sacrificed for quantity. Entire books have been written about cell structure and function and protein production. Stephen Hawking covered the contents of our astronomy class in the first few pages of A Brief History of Time. The stuff here is introductory material. Look at some science books, pay attention in science class. The GM probably knows a thing or two about real science, and if you know more, you can outfox him and come up with solutions the GM didn't think of.
The CSO is usually on an Away Team, so he should be ready for anything at all times.