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Question Video: Understanding How the Substrate Binds to an Enzyme Biology

A diagram of an enzyme and some substrates is provided. Which substrate will the enzyme bind to?


Video Transcript

A diagram of an enzyme and some substrates is provided. Which substrate will the enzyme bind to?

This question asks us to identify which substrate correctly matches with the enzyme we are given. To answer this correctly, let’s review the key facts about how enzymes work. Enzymes are biological catalysts, which means they speed up rates of reactions without being changed or used up themselves. They may work on just one substrate, for example, salivary amylase, which digests starch molecules down to the smaller maltose molecules. Or they may work on more than one substrate, for example, the ligases, which catalyze the joining of two molecules together. For this question, we will just refer to one substrate, as in the diagram.

Enzymes are important, as many essential reactions occurring within our cells are simply too slow to occur by themselves. Without enzymes, many basic life processes would be affected and we would not survive. All enzymes are made of one or more polypeptide chains, composed of many amino acids held together with peptide bonds. The order of amino acids along a chain determines the overall 3D shape of the enzyme due to their interactions with each other and the environment. This means that each type of enzyme has its own unique shape.

The active site is a specific region within this shape, where the substrate will fit. This question is asking specifically about the binding of a substrate and enzyme. So let’s now recap how this happens. The enzyme and its substrate must have complementary shapes to be able to fit together. In other words, they must fit together like jigsaw puzzle pieces. This means that enzymes will only operate on very specific substrates. Each enzyme, therefore, only catalyzes one specific reaction.

Having reviewed some key points about enzymes, let’s return to our question. In the diagram, the enzyme has a rectangular shape with a box cut out in the middle, representing the active site. Since the correct substrate will need to fit into this active site, it should have a structure that complements this and fits well. In other words, the substrate should have a protruding box to fit into this shape.

Therefore, the correct answer to our question “Which substrate will the enzyme bind to?” is V.

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