AQA Core Science - Will 280 UMS alway be a B grade?

if my total of all the exams plus my E on the ISA add up to 280 UMS point, would that still be a B grade? I need a B. Like say even if I got an E on the ISA but my overall UMS is 280, would that still be a B grade or would it not count because I got an E on the ISA? Thanks a lot to whoever answers this, I'll be more stress free in the exam if i can get an answer, thanks!