Just check what the requirements are at the schools you wish to apply to. Rule of thumb is 1 year of biology( with lab), 1 year of inorganic chemistry(with lab), 1 year of physics(with lab), 1 year of organic chemistry( with lab) and 1 year of math(calculus and or statistics). This is just a basic guideline, some schools might require more, but this is generally whats needed. Besides you want to have enough to prepare you for the MCAT as well.