Question: Is anything that’s alive kind of complicated?
Answer: Now that you mention it, yes.
Here’s a little (but this little is a lot) of what people have managed to figure out about what’s happening moment to moment in a wee, tiny little bacterium that has a fancy name (“Escherichia coli K-12 MG1655“). You can find the complete version of this diagram at the KEGG PATHWAY Database web site, which describes its own contents as “Wiring diagrams of molecular interactions, reactions and relations”