“You need to complete a minimum of 15 college-preparatory courses (A-G courses) with a letter grade of C or better. For courses completed during the 2020 winter, spring or summer terms, UC will also accept a grade of pass/credit. You must complete at least 11 of these courses prior to the beginning of your last year of high school.” - UC Admissions
This means that if your F was in an A-G course (Math, Science, History, English, Language, Visual Arts, and College Prep) you may not be eligible for admission to a UC. For more clarification, the best thing you can do is email one of the UC admissions offices with your situation and question and they will give you the most accurate answer.