You don't mention what exam board you are on - this would be helpful as "AS Biology new spec" could be from any of the exam boards so no one's going to be able to give you specific advice without it! :P
However, if you've learned it in class and it's in the textbook, it's a safe bet that it's something that you need to know. Although it may not be explicitly mentioned in the spec, it could be a part of one point e.g. "candidates must be aware of the stages of the cell cycle" or something similar.
tl;dr: learn it anyway!