I'm a senior and I'm struggling! How will this effect my admissions?

Senior year courses and grades will be shown on the final transcript to the college you matriculate to. College admission offers are generally conditional on completing the previously-reported in-progress courses with high enough grades. Some schools, like most UCs, tell you specifically what the threshold (as in a minimum GPA and no D or F grades). Other schools are more vague about wanting you to maintain your level of academic performance without giving a specific threshold.

CSULB’s conditions of admission are not too stringent:
http://web.csulb.edu/depts/enrollment/admissions/freshman_toa.html
SDSU’s conditions of admission state that “You must also maintain your reported overall grade point average.”
http://arweb.sdsu.edu/es/admissions/transfers/admitted/step1.html