Well you didn't list the following. So
Primary elements would be the sequence of amino acids
Secondary would be interactions between nearby residues, such as beta sheets and alpha helices
Tertiary would be the overall 3-D structure, including disulfide bonds
Quaternary refers to interactions among polypeptide chains
Answer:
A source of electricity, a wire coil, and an iron core
Explanation:
An electromagnet has three critical components:
1. A source of electricity
This is often a battery.
It generates the electric current that produces the magnetic field.
2. A wire coil
The wire carries the electric current.
Stacking the wire into loops makes a stronger magnetic field.
The more loops in the coil, the stronger the field.
3. An iron core
An iron core greatly increases the strength of the magnetic field within it and at its ends.