Keep in mind a file with 755 will be examined and run based on the magic number at the front of the file.
Even shell scripts. #! is actually a 16-bit magic number, that also happens to be a comment in almost every scripting language.
Go ahead - chmod +x a random non-executable file and try to run it. You'll probably get something enligthening: "invalid file (bad magic number): Exec format error"