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Question Video: Defining the Key Terms: Enzymes, Substrates and Active Sites Biology

Which of the following statements correctly links enzymes, substrates, and active sites? [A] The substrate has an active site that has a complementary shape to a range of enzymes. [B] The enzyme has an active site that has a complementary shape to a specific substrate. [C] The enzyme has an active site that has an identical shape to a range of substrates. [D] The substrate has an active site that has an identical shape to a specific enzyme. [E] The enzyme’s active site is constantly changing to have a complementary shape to a range of substrates.

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Video Transcript

Which of the following statements correctly links enzymes, substrates, and active sites? (A) The substrate has an active site that has a complementary shape to a range of enzymes. (B) The enzyme has an active site that has a complementary shape to a specific substrate. (C) The enzyme has an active site that has an identical shape to a range of substrates. (D) The substrate has an active site that has an identical shape to a specific enzyme. (E) The enzyme’s active site is constantly changing to have a complementary shape to a range of substrates.

The question asks us to find a statement that correctly links enzymes, substrates, and active sites. In order to answer this question, let’s go over the definition of each of these terms.

An enzyme is often referred to as a biological catalyst because it speeds up the rate of reactions by lowering the activation energy required for the reaction to take place. These molecules are never used up in the reaction. Instead, they are recycled. Every enzyme has an active site, which is a region on the surface of the enzyme where its specific substrate will bind to. A substrate is a single molecule, or a combination of molecules, that has a complementary shape to the enzyme’s active site. This allows the enzyme and substrate to bind together and form the enzyme–substrate complex. Once the enzyme and substrate bind via the enzyme’s active site, thereby forming an enzyme–substrate complex, the substrate is converted into its products.

Now that we have defined enzymes, substrates, and active sites, we can take another look at our answer choices. We need to find an answer that attributes the active site to the enzyme, since it is the enzyme that contains the active site and not the substrate. We also need to find an answer that highlights the complementarity between the enzyme’s active site and its specific substrate.

Therefore, the correct answer to our question is answer choice (B). The enzyme has an active site that has a complementary shape to a specific substrate.

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