Different direction from different schools. Check specific websites for specific school requirements. Some won't look at the app at all without prereqs. Biochem is normally encouraged/recommended but not required.
Rule of thumb is that prereqs need to be finished before matriculation or sometimes you can get accepted with the requirement that you finish specific classes before you are formally accepted. Your application as a whole is definitely not as strong without the prereqs, making it more difficult to get through the admit process. However, maybe you have a PhD in Biochemistry but for some reason never took physics/calc. If you are a non-traditional the potential strength of the rest of your application could offset the lack of all prereqs, if your scores and GPA are in the range.