Chose a harder schedule; went somewhat wrong.

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Getting a C+ in a prerequisite course will certainly not help your cause, but many a premed have done mediocre in a class or two and gotten accepted. So to answer your question: no, it's not negligible and yes, you should probably be a little concerned because the onus is on you to do really well this next year to show that this semester was a fluke. It also goes without saying that you should work towards getting a high MCAT score.
 
Can you switch to Physics 2 for the life sciences?
 
Having a couple of C's shouldn't significantly impact your application as long as you do well during the rest of your undergraduate career and finish with a strong BCPM GPA (Biology, Chemistry, Physics, and Math). Schools will see your year-to-year trends for your overall GPA and BCPM GPA so doing well during your junior and senior years will help.

See if you can switch to Physics for Life Science Majors. Either way, make sure to maximize your resources for Physics II. Go to office hours for your professor and TA, see if there's tutoring options on campus, form study groups, etc.
 
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