I took two science classes each semester while I was taking my prerequisites and didn't have any problems. But it is a lot of work, especially with lab.
Micro is strictly memorization and the textbook(s) contain way too much information to try and comprehend; therefore, most professors will provide handouts for the lectures. Study the handouts and only consult the book should you need additional understanding of a concept. I thought the labs were much more technical than chemistry and biology labs, but weren't too terribly involved. If you do well on the lab practicals you should do well in the lab component of the class. Bottom line is that micro is just information intensive
Organic chemistry is a different animal. For exam purposes, not only must you know how to name and draw organic structures, but you also must know all of the functional groups and what properties they confer to the molecules to which they are attached. You must also know reactions and mechanisms of reaction and given either a reactant or a product, draw the appropriate reaction. In this instance it really pays to know the various reagents utilized in organic chemistry as they are often reaction-specific. This is a course where rote memorization will help you some, but you must know the concepts. A huge differentiation from micro.
You didn't mention if the organic chemistry class was 3 or 5 credits. My comments assume it is a 5 credit class. If it is 4 credits you might be only getting an introduction to organic chemistry, in which case both lecture and lab will be watered down significantly.