Ch.10 Proteins Workers of the Cell

Frost - General, Organic and Biological Chemistry 4th Edition

Frost4th EditionGeneral, Organic and Biological ChemistryISBN: 9780134988696Not the one you use?Change textbook

Frost 4th Edition

Ch.10 Proteins Workers of the Cell

Problem 88

Chapter 6, Problem 88

The enzyme sucrase catalyzes the hydrolysis of the disaccharide sucrose but not the disaccharide lactose. Does the induced-fit or lock-and-key model explain the action of sucrase better? Explain.

Verified step by step guidance

Understand the two models of enzyme action: The lock-and-key model suggests that the enzyme's active site is a perfect fit for the substrate, like a key fitting into a lock. The induced-fit model proposes that the enzyme's active site undergoes a conformational change to better fit the substrate upon binding.

Identify the specificity of sucrase: Sucrase catalyzes the hydrolysis of sucrose but does not act on lactose. This indicates that sucrase has a high specificity for its substrate, sucrose.

Analyze the lock-and-key model: According to this model, sucrase's active site would be a perfect match for sucrose, but it would not fit lactose due to differences in molecular structure.

Analyze the induced-fit model: This model suggests that sucrase's active site adjusts its shape to accommodate sucrose, but it cannot adjust sufficiently to bind lactose due to structural incompatibility.

Conclude which model fits better: The induced-fit model better explains the action of sucrase because it accounts for the enzyme's ability to adapt to the substrate's shape while maintaining specificity, which aligns with sucrase's selective action on sucrose and not lactose.

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Key Concepts

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

Induced-Fit Model

The induced-fit model of enzyme action suggests that the enzyme's active site is flexible and can change shape to better fit the substrate upon binding. This model emphasizes the dynamic nature of enzyme-substrate interactions, allowing for a more precise fit that enhances catalytic efficiency. In the case of sucrase, this model may explain how the enzyme adapts to the specific structure of sucrose, facilitating its hydrolysis.

Lock-and-Key Model

The lock-and-key model posits that enzymes and substrates fit together in a rigid, complementary manner, much like a key fits into a lock. This model implies that the active site of the enzyme is specifically shaped to match the substrate, allowing for a straightforward interaction. While this model provides a clear visualization of enzyme specificity, it may not fully account for the flexibility observed in enzyme-substrate interactions, particularly for sucrase.

Enzyme Specificity

Enzyme specificity refers to the ability of an enzyme to selectively catalyze a particular reaction for a specific substrate. This property is crucial for biological processes, as it ensures that enzymes only act on their intended substrates, preventing unwanted reactions. In the context of sucrase, its specificity for sucrose over lactose highlights the importance of structural compatibility and the underlying mechanisms that dictate enzyme function.

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Textbook Question

What type of interactions between an enzyme and its substrate help to stabilize ES?

Textbook Question

The enzyme trypsin catalyzes the breakdown of many structurally diverse proteins in foods. Does the induced-fit or lock-and-key model explain the action of trypsin better? Explain.

Textbook Question

Do the amino acids that are in the active site of an enzyme have to be near each other in the enzyme’s primary structure? If no, explain.

Textbook Question

Does each of the following statements describe a simple enzyme (no cofactor or coenzyme necessary), an enzyme that requires a cofactor, or an enzyme that requires a coenzyme?

c. contains vitamin B₆ in its active site

Textbook Question

Match the terms (1) active site, (2) lock-and-key model, and (3) induced-fit model with the following descriptions:

a. the portion of an enzyme where catalytic activity occurs

b. the active site adapts to the shape of a substrate

c. the active site has a rigid shape

Textbook Question

Does each of the following statements describe a simple enzyme (no cofactor or coenzyme necessary), an enzyme that requires a cofactor, or an enzyme that requires a coenzyme?

b. consists of one polypeptide chain in its active form