Question

Does each of the following statements describe a simple enzyme or an enzyme that requires a cofactor? a. contains only amino acids b. has four subunits of polypeptide chains c. requires \(\mathrm{Fe}^{3+}\) in the active site for catalytic activity

Short answer

Statements (a) and (b) describe simple enzymes, while statement (c) describes an enzyme that requires a cofactor.

Step-by-step solution

- Analyze Statement (a)

Statement (a): Contains only amino acids. An enzyme made up entirely of amino acids without any additional components is a simple enzyme. Therefore, statement (a) describes a simple enzyme.

- Analyze Statement (b)

Statement (b): Has four subunits of polypeptide chains. Enzyme subunits refer to the individual protein molecules that combine to form a functional enzyme. Since this does not mention any non-protein components, it describes a simple enzyme.

- Analyze Statement (c)

Statement (c): Requires \( \mathrm{Fe}^{3+} \) in the active site for catalytic activity. The need for \( \mathrm{Fe}^{3+} \) (an iron ion) indicates that the enzyme requires a cofactor for its activity. Therefore, statement (c) describes an enzyme that requires a cofactor.

Key concepts

Simple Enzyme

A simple enzyme is an enzyme that is composed entirely of amino acids, without any other components. These proteins can perform their catalytic activities on their own, without the need for any additional molecules or ions.

Enzymes are biological catalysts. They speed up reactions essential for life. When an enzyme is referred to as 'simple', it means its structure is made purely of amino acids, the building blocks of proteins. These enzymes are self-sufficient and don't require other substances to function.

For instance, consider statement (a) from the exercise: 'contains only amino acids'. This indicates that the enzyme is a simple enzyme. Because it only has amino acids and doesn't rely on any external molecules to carry out its function.

Cofactor

A cofactor is a non-protein substance that binds to an enzyme and is essential for the enzyme's activity. Cofactors can be metal ions (like iron or magnesium) or organic molecules (such as vitamins).

Consider statement (c) from the exercise: 'Requires \(\text{Fe}^{3+}\) in the active site for catalytic activity'. Here, \(\text{Fe}^{3+}\) is an iron ion acting as a cofactor. The enzyme relies on this ion to perform its catalytic role.

Not all enzymes need cofactors. But for those that do, the binding of the cofactor to the enzyme is crucial for the activation and function of the enzyme. Without the cofactor, the enzyme would be inactive and unable to catalyze the reaction.

Enzyme Subunits

Enzyme subunits are the individual protein molecules that come together to form a functional enzyme. These subunits can create complex structures, each contributing to the overall activity of the enzyme.

In the context of statement (b) from the exercise: 'Has four subunits of polypeptide chains'. This indicates that the enzyme is composed of four protein subunits.

Subunits allow enzymes to be versatile and efficient. They can regulate activity and enable enzymes to perform complex reactions. For example, hemoglobin is made up of four subunits, each allowing it to carry oxygen efficiently in the blood.

Though the presence of multiple subunits makes an enzyme complex, it may still be classified as a simple enzyme if these subunits are solely made of amino acids and don't require any cofactors.