When oxygen binds to a heme-containing protein, the two open coordination bonds of fe2+ are occupied by: ?

I believe that the two open coordination bonds of Fe2+ are occupied by one oxygen molecule and one amino acid atom. 
Heme protein is a protein that contains a heme prosthetic group. The heme group confers functionality, which can include oxygen carrying, oxygen reduction, electron transfer, and other processes. Hemoglobin contains four heme units in total, allowing four oxygen atoms in total to bind to the protein.

Olive oil? i don’t really have enough info for the q?

The proton has a positive charge while the neutron has no charge they both make up the nucleus of the atom while the elections have a negative charge and surround the nucleus of the atom. the protons and electrons are used to calculate the atom's mass whereas the neutrons don't affect the mass