I've been working as a PCA on a General Medicine floor for about 8 months now. I'm also a nursing student. I start my shifts by answering call lights and taking vitals, filling up water pitchers, turning and cleaning up patients and feeding them. I try to encourage those who can sit up in a chair for breakfast to do so. I know some places divide differently, but I have 6-9 patients, and I'm matched with one RN most of the time.
I try to be done with vitals and as much of the rest of the above in the first hour, but sometimes it takes two if patients have a lot of requests or if something unexpected happens.
In the morning I do baths next, then bloodsugar checks and repeat vitals (and don't forget about more call lights and turning).
Somewhere I take 10-15 minutes for breakfast, but before long it's time to pass out lunch trays and feed patients (usually I have one patient to help, but I have had up to four--I call for reinforcements when that happens). Almost everyone needs help sitting up in bed or help getting to a chair so they don't fall.
I try to take my lunch about a half an hour after trays are passed (I'd take it right away, but there are usually a few errands to run first--lunch order changes, feeding, etc.)
After lunch I record intake and output, and I turn and reposition people or clean them up once again. I also double check that I had time to document everything.
This is the nitty gritty of the job, but unfortunately I can't really describe well enough what I love about working on general medicine. What I can tell you is that I get to learn about all kinds of patients and a huge variety of illnesses. Visually, I am starting to be able to identify aceites (fluid buildup often caused by liver failure), common signs of CHF (congestive heart failure), and associated problems of renal disease (I had never really realized that people with kidney failure didn't always make urine). I am also starting to know when a patient is going downhill, in the time that I take their vital signs.
That's the science of it (an anatomy and physiology class would help you tremendously, BTW). The other great thing about the job is knowing that you are helping the patient get better (for example, that bedsores are going to be healing under your care). It's very nice to have a patient all tucked in "like somebody loves them" as another PCA said once.
You're going to be spending a great deal of time with these patients, and some of them are rather high acuity. You can save a patients life by alerting your nurse when you notice their respirations are inadequate or that the patient is suddenly "not acting right." (A patient's blood sugar dropped to 17 the other day after dialysis). Make sure you tell the nurse immediately when vitals are out of wack, or when something else is not quite the way it should be. You'll learn what is a priority if you pay attention and ask questions. Good luck!