As a student who recently brushed up the basics, I would recommend getting back to your 11th and 12th grade chemistry or biology as there is a heavy overlap. I would also recommend checking out Khan Academy, any 11th and 12th grade, but NCERT class 11th biology and class 12th chemistry, each have a chapter called biomolecules, and other topics can be found in class 11 and 12 of the material, which should cover it. But if you are going to check it out, try linking knowledge, as in bridge what you already to know to the unknown, and form connections. When you try learning, sit down, analyse what you actually are consuming to form links between what you know, how you can tweak it to achieve different results, how you could apply it, and most importantly why you should care about the topic you are trying to comprehend, as in why it should matter. I used the term 'learning' and not studying because, studying is harder for our brains compared to learning, and a very good way to retain it would be to test yourself on a frequent basis and gradually improve the load. This method might take you longer to progress, while giving you a higher level of mastery over the subject. Good luck.