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Ch. 8 - Energy and Enzymes: An Introduction to Metabolism
Chapter 8, Problem 4

Which of the following correctly describe an active site? Select True or False for each statement. T/F It is the location in an enzyme where substrates bind. T/F It is the place where a molecule or ion binds to an inactive enzyme to induce a shape change to make it active. T/F It is the portion of an enzyme where chaperones bind to help enzymes fold. T/F It is the site on an enzyme where catalysis occurs.

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Step 1: The active site of an enzyme is the region where the substrate binds. So, the statement 'It is the location in an enzyme where substrates bind.' is True.
Step 2: The active site is not typically where a molecule or ion binds to induce a shape change in the enzyme. This usually occurs at a different site, known as the allosteric site. So, the statement 'It is the place where a molecule or ion binds to an inactive enzyme to induce a shape change to make it active.' is False.
Step 3: Chaperones are proteins that assist in the folding of other proteins, including enzymes. However, they do not typically bind at the active site of the enzyme. So, the statement 'It is the portion of an enzyme where chaperones bind to help enzymes fold.' is False.
Step 4: The active site is indeed where the enzyme catalyzes the reaction, converting the substrate into the product. So, the statement 'It is the site on an enzyme where catalysis occurs.' is True.
Step 5: In summary, the active site of an enzyme is the location where substrates bind and where catalysis occurs. It is not typically the site where allosteric regulators bind or where chaperones assist in protein folding.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Active Site

The active site of an enzyme is a specific region where substrate molecules bind. This site is typically a pocket or groove on the enzyme's surface, formed by the unique three-dimensional structure of the enzyme. The shape and chemical environment of the active site facilitate the conversion of substrates into products during the catalytic process.
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Enzyme Activation

Enzyme activation refers to the process by which an enzyme becomes functional, often through the binding of a molecule or ion. This binding can induce a conformational change in the enzyme, allowing it to adopt the correct shape for substrate binding and catalysis. This concept is crucial for understanding how enzymes can be regulated and activated in biological systems.
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Catalysis

Catalysis is the process by which an enzyme accelerates a chemical reaction. The active site plays a critical role in this process by lowering the activation energy required for the reaction to occur. This allows the enzyme to convert substrates into products more efficiently, making catalysis a fundamental concept in biochemistry and molecular biology.
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Related Practice
Textbook Question

What is a transition state? a. the shape adopted by an enzyme that has an inhibitory molecule bound at its active site b. the amount of kinetic energy required for a reaction to proceed c. the intermediate complex formed as covalent bonds in the reactants are being broken and re-formed during a reaction d. the enzyme shape after binding an allosteric regulatory molecule

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Textbook Question

How does pH affect enzyme-catalyzed reactions? a. Protons serve as substrates for most reactions. b. Energy stored in protons is used to drive endergonic reactions. c. Proton concentration increases the kinetic energy of the reactants, enabling them to reach their transition state. d. The concentration of protons affects an enzyme's folded structure and reactivity.

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Textbook Question

What factors determine whether a chemical reaction is spontaneous or not?

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Textbook Question

Explain the lock-and-key model of enzyme activity. What is incorrect about this model?

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Textbook Question

If you were to expose glucose to oxygen on your lab bench, why would you not expect to see it burn as described by the reaction in Figure 8.6? a. The reaction is endergonic and requires an input of energy. b.The reaction is not spontaneous unless an enzyme is added. c. The sugar must first be phosphorylated to increase its potential energy. d. Activation energy is required for the sugar and oxygen to reach their transition state.

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Textbook Question

In Figure 8.10, the energetic coupling of substrate phosphorylation and an endergonic reaction are shown. If the hydrolysis of ATP releases 7.3 kcal of free energy, use the graph in this figure to estimate what you would expect the ∆G values to be for the uncoupled reaction and the two steps in the coupled reaction.

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