Which statement is TRUE regarding the active sites of enzymes?

Question

BlackTom AI · Accepted Answer

To begin, consider the question asking which statement is TRUE about the active sites of enzymes and then evaluate each option in turn.
Option 1: 'Active sites are unique microenvironments.' This is correct. The active site is a specifically shaped pocket or groove where substrates bind, and it often provides unique chemical conditions (pH, polarity, aligning catalytic residues) that favor the chemical reaction. The environment is tailored to stabilize transition states and lower the activation energy.
Option 2: 'Only amino acids close in sequence can be close together in the active site of the folded protein.' This is inaccurate. The folded protein can bring amino acids that are distant in the primary sequence into close spatial proximity in the three-dimensional structure, forming the active site even though they are not adjacent in sequence.
Option 3: 'The active site takes up a large part of the total volume of an enzyme.' In reality, the active site is typically a small, specific region of the enzyme, not a large portion of the enzyme's overall volume. Enzymes are efficient because only a small region is involved in catalysis.
Option 4: 'Substrates are bound to enzymes by multiple covalent bonds.' Substrate binding to the active site is usually via noncovalent interactions such as hydrogen bonds, ionic interactions, van der Waals forces, and hydrophobic effects. Covalent catalysis is relatively rare and not the typical mode of binding for substrates.
Overall, option 1 is the true statement, while options 2, 3, and 4 misstate typical features of enzyme active sites and substrate binding.

Which statement is TRUE regarding the active sites of enzymes?单项选择题

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