You haven't mentioned the name of the examination you are talking about, in the question. Kindly restructure your question and ask again tagging or including the name of the exam along with the other necessary information. This helps us to provide with the correct guidance. You acn also ask in the comments section.
If it is for the NEET UG, 2020 entrance exam, the link given below may help you with the weightage of topics-
Hope this helps.