The SAT and MCAT are very RELATED skills. That's not to say that anybody, at this time, can establish any kind of prediction using just the SAT. An excellent SAT score is a good sign for an excellent MCAT score, and poor scores are a bad sign, but the exact math is unclear.
Second, biology and physical science are NOT content-based. They are also reading comprehension. They just happen to be reading ABOUT biology and physical science.