Question

Does each of the following statements describe a simple enzyme or an enzyme that requires a cofactor? a. contains ${\mathrm{Mg}}^{2+}$ in the active site b. has catalytic activity as a tertiary protein structure c. requires folic acid for catalytic activity

Short answer

a. requires a cofactor, b. simple enzyme, c. requires a cofactor

Step-by-step solution

Analyze statement (a)

Statement (a) mentions that the enzyme contains ${\text{Mg}}^{2+}$ in the active site. Enzymes that require a metal ion or other non-protein molecule for activity are known as holoenzymes, where the non-protein part is called a cofactor. Since ${\text{Mg}}^{2+}$ is a cofactor, this describes an enzyme that requires a cofactor.

Analyze statement (b)

Statement (b) indicates the enzyme has catalytic activity as a tertiary protein structure. A simple enzyme functions without the need for cofactors if its tertiary structure alone is sufficient for catalytic activity. Therefore, this describes a simple enzyme.

Analyze statement (c)

Statement (c) specifies that the enzyme requires folic acid for catalytic activity. Folic acid acts as a coenzyme, which is a type of cofactor. Therefore, this describes an enzyme that requires a cofactor.

Key concepts

simple enzyme

Let's start by exploring what a simple enzyme is. A simple enzyme is an enzyme that consists entirely of protein and does not require any additional molecules to be fully functional. This type of enzyme relies solely on its intricate three-dimensional structure to carry out its catalytic activity.
The tertiary structure of the protein forms an active site where the substrate binds and reactions take place. In summary:
- Simple enzymes are purely protein.
- They function without needing cofactors or coenzymes.
- Their catalytic activity is dependent on their protein structure alone.
An example of a simple enzyme is ribonuclease, which breaks down RNA molecules without requiring any assistance from non-protein components.

holoenzyme

In contrast to a simple enzyme, a holoenzyme is a more complex structure. It consists of an apoenzyme (the protein component) and one or more cofactors, which are non-protein molecules.
These cofactors are essential for the full catalytic activity of the enzyme. The holoenzyme is the complete, active form of the enzyme that can efficiently catalyze biochemical reactions.
- Holoenzymes are made up of both protein (apoenzyme) and non-protein (cofactor) elements.
- They achieve catalytic activity through the combined efforts of both components.
An example of a holoenzyme is DNA polymerase, which requires metal ions such as Mg²⁺ to function properly.

cofactor

Cofactors are crucial for the functionality of some enzymes. They can be either inorganic molecules, such as metal ions, or organic molecules, known as coenzymes. Cofactors bind to the enzyme and often play a direct role in the catalytic process.
If the cofactor is an organic molecule, it's called a coenzyme (we'll cover this next).
- Cofactors can be inorganic (like metal ions) or organic (like vitamins).
- They are not proteins, but they assist enzymes by stabilizing their structure or even participating in chemical reactions.
Two primary examples are:
- Metal ions like Mg²⁺ or Fe²⁺
- Vitamin-derived molecules like NAD⁺

coenzyme

Coenzymes are a specific type of cofactor. They are organic molecules, often derived from vitamins, that bind to the enzyme, usually temporarily, and are essential for the enzyme's function.
Coenzymes often act as carriers for chemical groups or electrons during the reaction.
- Coenzymes are organic molecules, originating commonly from vitamins.
- They work by transferring various groups or electrons between molecules, facilitating enzymatic reactions.
Examples of coenzymes include:
- NAD⁺ (Nicotinamide adenine dinucleotide)
- Folic acid, which is used in various enzyme reactions related to DNA synthesis
By understanding these types of enzyme components, you get a clearer picture of how enzymes work in biological processes.