In Queensland, the traditional pre-med degree is biomedical science. In my opinion, this is a tradition without any real logical foundation. This is the case for a couple of reasons.
First, a biomedical science degree does not adequately prepare you for GAMSAT - it prepares you for medical school (and even this it does poorly - see later). These are two different things. Most people miss this. A biomedical science degree does not give you adequate opportunity to develop your writing skills for Section II and emphasises rote learning which does not develop your decision making ability in a pressured scenario based environment like Section I. Further, the course structure only covers basic first year organic chemistry which is insufficient to do well on Section III.
Second, though a biomedical science degree covers anatomy, physiology and pharmacology, other, more reputable courses such as pharmacy perform the same task while actually providing an opportunity for proper employment at the completion of the degree. The level of clinical knowledge of pharmacy students is also far superior to that of biomedical science students who know enough to 'sound' competent but not enough to be useful in a clinical setting. Admittedly, it is difficult to find work as a pharmacist but if your end goal is to become a doctor, the knowledge you gain as a pharmacy student will far exceed anything you will ever gain as a biomedical science student. In my view, it is definitely worth the hard slog.
So what should you do if you are a biomedical science student? I would structure my course so that I could complete organic chemistry to 2nd year university standard. I would then also use my electives to complete a few arts subjects so that I could develop my writing ability. Another alternative would be to enrol in a dual program such as commerce/science so that you have a good fall back option should the medical school path not work out. This has the added benefit of widening your field of knowledge, providing scope for employment both prior to and during medical school and exposing you to non-rote learning based assessment methods and essay writing which will only serve to assist you in Section I and Section II.
If you can't structure your course appropriately (maybe you are too far into your program etc), look to other opportunities to develop your writing skills. Do a writing course or enrol in a second degree and cherry pick the subjects you want (you don't have to finish the whole degree). Join the debating club!
Entry to medical schools is getting more competitive and the cost of being a student for so long is becoming prohibitively expensive. Do your best to read between the lines of the university course guides and make your selections based on practical considerations.
It's a sad indictment upon our university system that the liberalisation of education (you can get a piece of paper for just about anything these days) has meant that there a number of meaningless degrees out there. Most of these degrees do not prepare you for what they indicate they will and do not lead to useful employment opportunities. We are definitely in the age of the educated unemployed. Look for the underlying value - "what is the practical outcome of all of this" is what you should be saying to yourself. Don't get me wrong, I've got a BSc, I learnt things, but there are better options out there! :)
Best of luck with the study!