Which of the following is often true of the active sites of enzymes?

• A. They are highly specific to the substrate they bind.
• B. They are located on the surface of the enzyme and are identical in all enzymes.
• C. They function only at extremely high temperatures.
• D. They are composed entirely of non-polar amino acids.

Answer: (A)

Verified step by step guidance

1. Understand the role of the active site in enzymes: The active site is the region on the enzyme where the substrate binds and the chemical reaction occurs. It is crucial for the enzyme's function.
2. Recognize the specificity of active sites: Active sites are highly specific to the substrate they bind due to their unique shape and chemical properties. This specificity is often described using the 'lock and key' model or the 'induced fit' model.
3. Clarify the location of active sites: Active sites are typically located on the surface of the enzyme, but their structure and function vary between different enzymes. They are not identical in all enzymes.
4. Address temperature and amino acid composition: Enzymes function within a specific temperature range, often optimal at moderate temperatures, not extremely high ones. Active sites are composed of a mix of polar and non-polar amino acids, depending on the enzyme's function and the substrate's properties.
5. Conclude with the correct characteristic: The active site of an enzyme is highly specific to the substrate it binds, which is a key feature of enzyme functionality.