Yes you can. But you are only in your first year, just follow the plan because those subjects all provides the second year prerequisites for ALL medical science majors.
And uoc is just Units of Credit, same as Units in the HSC. You can do a maximum of 24 Units per session, 48 units per year. in your case, you do 6 bio, 6 chem, 6 maths, and 6 electives, giving you a total of 24 UOC.