MCAT prep course or Cell Biology in summer school

Between sophomore and junior years in college, which would be more helpful? A summer school session taking cell biology or taking MCAT prep course?

Will you have completed biochemistry by the end of your sophomore year? Physics?

When you plan to sit for your MCAT?

There’s no sense taking a prep class until you have finished all the needed pre-reqs and are planning on taking the MCAT immediately after you finish the prep class.