A similar often asked "JC version" of this question relates to
"If I only have combined science at 'O' levels, will I be at
a disadvantage compared to Pure Science students, when taking
H2 Science?"
Generally, the answer is - any disadvantage is very slight and
can easily be overcome (and very quickly, within a month) by
effort to catch up.
'O' level combined science is like level 1.5 difficulty &
content.
'O' level pure science is like level 2.0 difficulty &
content.
JC H2 science and Poly diploma science is like level 10.0
difficulty & content.
University science is like level 50+ difficulty
& content (all the way to level 1000+ at PhD).
Because 'O' level science is really just kiddy-play in
comparison, and the real learning *begins* at JC & Poly level
(actually it's still a warm-up for real learning at University
level), so it really doesn't make much of a difference whether you
took combined or pure science at 'O' levels, as long as you're now
(at JC or Poly level) willing to *begin* your real
learning.