If you dont buy obamacare,you will be subject to a 750 dollar fine?

for a family of 4.i ume it might be less? for a single.i can buy accidental injury insurance for about 20 bucks a month(broken legs etc.).ok then i pay the 750 dollar (fine).under obamacare the insurance company cant deny me for a preexisting-condition.so if i go to a doctor and he tells me i need a heart transplant i can go buy insurance and im covered? wtf