Sounds frustrating. Disorganization may or may not be a measure of quality here. You're doing the right thing to question whether you can depend on the lecturers: odds are, you have to take ownership. Let me throw out some thoughts that may or may not apply to you.
I'm curious to know what you're comparing these science classes to. How do they compare to, say, a math class at the same school? Are you, maybe, coming from a small private school into a big public school?
If you haven't taken any hard science before, you may be experiencing a kind of panic attack where you're looking for ANYTHING to explain your stress level. This stuff is really hard, and taking it on can be completely overwhelming - I've seen more than one nervous breakdown in my classmates. I suggest that you pick out a couple of the calm overachiever 19 year olds sitting in the front row, and ask them if they're having the same experience as you. If they're managing, you have to manage too.
You can assume that questionable lecture quality is a permanent problem that you'll have to deal with in med school as well. It's a given that you'll have lecturers who speak with very thick impenetrable accents, who are painfully shy, who are hostile, who want a bully pulpit, who have Asberger's, etc. You have to succeed anyway. Aargh.
In these classes, do you get a syllabus? Does the syllabus lay out what subjects are covered, in what order, and what textbook activities you should be doing for each subject? Do you have the info necessary to take charge of the coursework?
You can find a list of the subjects on the MCAT on the AAMC website,
here. When you're just starting prereqs, it all looks like gibberish, but after maybe the first exam you can start ticking off topics. Fundamentally, and I think you realize this already, when you start preparing to take the MCAT, you need to be
reviewing, not learning, the material.
Lastly, it's common, particularly among nontrads who have worked in professional industries, to be discouraged by disorganization in what should be very standardized material. I continue to be amazed by faculty and support staff who are intimidated by the internet, who think that students using recording devices are going to
sell a lecture MP3 for actual money, who put up a powerpoint that doesn't match the copy students get (printed or online) and can't figure out why that might be a problem, etc. And it's a rarity to have a professor who doesn't get way behind and then shove a boatload of material onto you in the last week of the term.
Sigh.
Best of luck to you.