Which of these statements about enzyme inhibitors is true?

• A. A competitive inhibitor binds to the enzyme at a place that is separate from the active site.
• B. A noncompetitive inhibitor does not change the shape of the active site.
• C. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback.
• D. Inhibition of enzyme function by compounds that are not substrates is something that only occurs under controlled conditions in the laboratory.
• E. The action of competitive inhibitors may be reversible or irreversible.

Answer: (E)

Verified step by step guidance

1. Understand the role of enzyme inhibitors: Enzyme inhibitors are molecules that bind to enzymes and decrease their activity. They can be classified into different types based on their mechanism of action.
2. Differentiate between competitive and noncompetitive inhibitors: Competitive inhibitors bind to the active site of the enzyme, competing with the substrate. Noncompetitive inhibitors bind to a different site, causing a change in enzyme shape that reduces its activity.
3. Evaluate the statement about competitive inhibitors: A competitive inhibitor binds to the active site, not a separate place. Therefore, the statement that a competitive inhibitor binds to a separate place is incorrect.
4. Assess the statement about noncompetitive inhibitors: Noncompetitive inhibitors do change the shape of the enzyme, affecting the active site indirectly. Thus, the statement that they do not change the shape is incorrect.
5. Consider the nature of enzyme inhibition: Enzyme inhibition can occur naturally in biological systems, not just under laboratory conditions. The statement about inhibition only occurring in labs is incorrect. The correct statement is that competitive inhibition can be reversible or irreversible, depending on the inhibitor's nature.