linear A level

With this A level being linear starting 2015, can you still take AS external exams for subjects required for Medicine (Chemistry, Biology)? What is the procedure, just apply to take exams from what you studied in Year 12? And then continue in Year 13?

Maybe stupid question, but I am confused: are AS and A levels different curriculum?

Thank you for details.

http://www.osfc.ac.uk/parents/a-level-change-september-2015/
This is for my local sixth form but it's very informative and will be similar to the spec you'll be studying!

Thank you so much!
But I am still confused: those 3 or 4 A level subjects selected in second year mean that you have to study in one year (the second one) the whole syllabus you should study in 2 years? Do you understand what I mean?