When you first begin your background research you may use sources you are accustomed to such as textbooks, Wikipedia and Google searches. But once you get deep enough in your research to need actual scientific articles you will want to use some specific databases that store scientific papers. Common databases used by biologists are:
NCBI pubmed database, and a tutorial on using pubmed
Generally you will use these databases to search for papers in a research area (using keywords) or for specific papers (for example if you want to look up a reference you found on a Wikipedia page). When selecting the keywords to use in your search consider including topics (such as DNA damage, chemotaxis, pathogen avoidance, etc.), model systems (E. coli, stem cells, mice, etc.), genes/proteins (cdc4, map kinase, etc.) and pathways/mechanisms (apoptosis, dna damage, chemotaxis, etc.). It is often a good idea to start with either a narrow search (many specific keywords) and broaden (reduce the number of keywords) or to start with a broad search and then narrow it down until you get to a manageable number of papers to sort through. To search for a specific paper (say you were reading another paper and wanted to look up one of their references) you could search using the author’s last names and the title of the paper.
When you find articles using an online search database you may be restricted in how much of the article you can view (title only, abstract only, or the full article). Some journals require a subscription to view their published papers. If you are affiliated with a College or University you can access papers in journals that the school has a subscription to but may need to be on campus or log in through the library’s website.