Prereqs for Biochem 3G03 are two terms of orgo, OR biochem 2b03 and 2bb3, OR a bunch of other options. Key word being OR, and not AND. And iSci 2A18 is a substitute prerequisite for both chem 2b03 and 2bb3.
Thoughts: don't worry about this! 3G03 probably just wants students who have done at least some biochem, and not necessarily 2 terms of orgo chem specifically.
Myles - substitute prerequisite means that if you want to take a course that requires that you took Biochem 3G03, then you can still take it having done iSci 2A18.