Usually the easiest way to find a good EPQ question is to draw on two interests you might have within biochemistry. Think about adding things to your title like: What influence does X have on Y, or How does the use of X affect Y etc. Try to be as specific as you can without narrowing down your topic too much- if you're tackling a broad topic like bioluminescence your teacher will probably tell you to find a 'niche' so you can have a targeted discussion (eg. Are you focusing on bioluminescence in plankton specifically? As a defence mechanism? To attract prey?). Depending on how specific your question is, a good way to narrow it down is geographically or within a certain parameter.
I would suggest doing as much research on the broad topics you're interested in first, as this will help you with that. Read some papers or articles online (JSTOR is God sent) about bioluminescence/and or animal life spans and the more you read the more you'll be able to find a clearer narrative. You'll find it difficult to form an argument or a title just out of one topic you're interested in without much background research.
But don't worry! It took me ages to figure out my title and you can change it again and again- in fact, the examiners love when you change your title as your project progresses as long as you note down your changes and explain why. As long as you're interested in the topic, and you can see yourself spending a lot of time reading about it- the title will come!
Hope this helps xx