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Those comments don’t make sense to me. 5.111 is Principles of Chemical Science - it has nothing to do with biology (the intro class of which is 7.012, as is said above, though one of the professors for it is LANDER, not Langer). 3.091 is probably what you’re thinking of - Introduction to Solid State Chemistry - which no one in his or her right mind would take in addition to 5.111.</p>