Which electron orbits will fill first with electrons?

The closest orbital to the nucleus, called the 1s orbital, can hold up to two electrons. This orbital is equivalent to the innermost electron shell of the Bohr model of the atom. It is called the 1s orbital because it is spherical around the nucleus. The 1s orbital is always filled before any other orbital.

membrane and cell wall

Explanation: this is because the cell wall is only known to happen in plant cells and a membrane is in both plant and animal cells so it is most likely membrane and cell wall.