Final answer:
The protein component of a conjugated enzyme is called an apoenzyme and the complete enzyme with its non-protein cofactor is called a holoenzyme.
Step-by-step explanation:
The protein in a conjugated enzyme is referred to as the apoenzyme, whereas the combination of the protein and the non-protein cofactor is known as the holoenzyme. Cofactors can be inorganic ions, such as Fe²⁺ or Mg²⁺, or they can be organic molecules, which are typically referred to as coenzymes.
Coenzymes are often derived from vitamins and are essential for the proper functioning of enzymes. Some enzymes entirely consist of amino acid chains, but there are also many that require these non-protein molecules, either temporarily through ionic or hydrogen bonds or permanently through stronger covalent bonds.
Examples of common coenzymes include NADH and ATP, which bind to enzymes and activate them by providing high-energy electrons or phosphate groups, respectively. Without a necessary cofactor or coenzyme, an enzyme is referred to as an apoenzyme and is generally inactive.