it depends on whether you did core & additional, or core, additional & further additional. it also depends on whether you mean raw marks or UMS marks.
i assume you did a separate biology gcse, as you specifically care about your biology grade. if this is the case you did three exams and one controlled assessment for biology - four things being remarked gives you a higher chance of gaining five extra marks.
if you didn't do a separate biology gcse and you did a core and additional gcse, you'll only have two biology papers to remark, so there's less of a chance. i don't know how the controlled assessments work for this because i did a separate biology gcse, but i assume your controlled assessments would be for overall core and overall additional rather than any being specifically biology.
if you did a core and additional gcse, the best case scenario would just be to get everything remarked, or at least everything that's only a few marks away from the next grade boundary.
i've been marked up 2 or 3 marks (i don't remember which, sorry) before to get a higher grade, so i imagine 5 is possible!