Chapter 2: Problem 15

Explain the active site theory of enzyme functioning. (p. 31)

Short Answer

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Answer: The active site theory of enzyme functioning is based on the concept that enzymes have specific sites, called active sites, where substrate molecules bind and undergo a chemical reaction. Enzymes function by lowering the activation energy required for reactions to occur, and their structure, including their active sites, is essential for this process. The lock and key model illustrates the specificity of enzyme-substrate interactions, as it likens the active site to a lock and the substrate to a key. In this model, only a specific key (substrate) can fit into the lock (active site), demonstrating the importance of accurately matching substrates to enzymes.

Step by step solution

1. Role of Enzymes in Chemical Reactions

Enzymes are biological catalysts that facilitate chemical reactions in living organisms. They increase the speed of reactions by lowering the activation energy required, allowing necessary biological processes to occur efficiently.

2. Structure of Enzymes

Enzymes are usually proteins, and their structure is essential to their function. They have a three-dimensional shape determined by the sequence of amino acids in their backbone. The arrangement of amino acids creates a unique structure with specific active sites.

3. Definition of an Active Site

An active site is the part of an enzyme where the substrate molecules bind and undergo a chemical reaction. It is a small, unique pocket or cleft on the enzyme's surface, with properties tailored to bind a particular substrate. The active site provides an optimal environment for the reaction to occur.

4. Binding of Substrates to the Active Site

Substrates, the reactants in enzyme-catalyzed reactions, bind to the active site of an enzyme through a process called enzyme-substrate (ES) complex formation. This binding is often governed by hydrogen bonds, electrostatic interactions, or hydrophobic interactions between the enzyme and substrate.

5. Lock and Key Model

The lock and key model is a simplified way to describe the active site theory of enzyme functioning. In this model, the active site has a fixed shape, acting like a lock, and the substrate represents the key that fits the lock precisely. When the substrate binds to the active site, the enzyme is then able to catalyze the chemical reaction. This model illustrates the specificity of enzyme-substrate interactions, as only the correct "key" (substrate) can bind to the "lock" (active site).

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Explain the active site theory of enzyme functioning. (p. 31)

Short Answer

Step by step solution

1. Role of Enzymes in Chemical Reactions

2. Structure of Enzymes

3. Definition of an Active Site

4. Binding of Substrates to the Active Site

5. Lock and Key Model

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