Are you penalised for spelling in science exams? I mean by spelling words slightly incorrectly however the meaning is clear and the misspelt word does not resemble another word. Example maybe in biology we are asked to name a disease and we write dyabetis instead of diabetes will we get no marks?
For Biology, no. As long as it sounds phonetically correct, they will give you the mark. However, if it is ambiguous as to what you're referring to, as with the whole glycogen/glucagon thing, then they aren't going to give you the benefit of the doubt if you write glycogon, but you will for glikojen (well, possibly...might be too extreme of an example). Hence for that reason, you're better off just learning the spellings. I think the same rule applies to other sciences, but I haven't had teacher confirmation on the rules in the others.