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 87

Chapter 6, Problem 87

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.

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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.

Consider the nature of trypsin: Trypsin is a protease enzyme that catalyzes the breakdown of proteins by cleaving peptide bonds. It interacts with a wide variety of structurally diverse proteins, which implies flexibility in its binding mechanism.

Evaluate the lock-and-key model: This model assumes a rigid active site that matches the substrate exactly. Given the structural diversity of proteins trypsin acts on, this model may not fully explain its mechanism.

Evaluate the induced-fit model: This model accounts for flexibility in the enzyme's active site, allowing it to adapt to different substrates. This adaptability aligns well with trypsin's ability to catalyze reactions for various proteins.

Conclude that the induced-fit model better explains the action of trypsin, as it accommodates the enzyme's ability to interact with diverse protein structures by adjusting its active site to fit each substrate.

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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. It accounts for the adaptability of enzymes to various substrates, making it particularly relevant for enzymes like trypsin that act on diverse protein structures.

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 enzyme's active site is specifically shaped to match a particular substrate, which limits the enzyme's ability to accommodate variations in substrate structure. While this model provides a straightforward explanation of enzyme specificity, it may not fully capture the complexities of enzymes like trypsin that interact with a wide range of protein substrates.

Enzyme Specificity

Enzyme specificity refers to the ability of an enzyme to selectively catalyze a particular reaction or act on specific substrates. This characteristic is crucial for understanding how enzymes like trypsin function in the digestive system, where they break down proteins into smaller peptides. The degree of specificity can influence whether the induced-fit or lock-and-key model better explains the enzyme's action, as trypsin's ability to adapt to various protein structures suggests a more flexible interaction.

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Textbook Question

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.

Textbook Question

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

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

Match the terms (3) substrate with the following descriptions:

a. has a tertiary structure that recognizes the substrate

b. is the combination of an enzyme with the substrate

c. has a structure that fits the active site of an enzyme

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