Skip to main content
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
All textbooksFrost 4th EditionCh.10 Proteins Workers of the CellProblem 95c
Chapter 6, Problem 95c

Pepsin, an enzyme that hydrolyzes peptide bonds in proteins, functions in the stomach at a pH optimum of 1.5 to 2.0. How is the rate of a pepsin-catalyzed reaction affected by each of the following conditions?
c. running the reaction at 0 °C

Verified step by step guidance
1
Understand the role of temperature in enzyme activity: Enzymes, including pepsin, are proteins that catalyze reactions. Their activity is highly dependent on temperature. At lower temperatures, such as 0 °C, the kinetic energy of molecules decreases, leading to slower movement and fewer effective collisions between the enzyme and substrate.
Recall the concept of the optimal temperature for enzymes: Most enzymes have an optimal temperature range where their activity is maximized. For pepsin, this optimal temperature is typically around human body temperature (37 °C). Deviating significantly from this range, especially lowering the temperature, reduces the enzyme's catalytic efficiency.
Consider the effect of 0 °C on reaction rate: At 0 °C, the enzyme's activity is significantly reduced because the molecular motion is slowed down. This results in a lower rate of reaction, as fewer substrate molecules interact with the active site of pepsin.
Relate temperature to enzyme structure: While 0 °C does not denature pepsin (denaturation typically occurs at high temperatures), it does cause the enzyme to function less effectively due to reduced flexibility in its active site, which is necessary for binding substrates.
Conclude the impact: Running the reaction at 0 °C will slow down the rate of the pepsin-catalyzed reaction significantly, as the enzyme's activity is hindered by the low temperature.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
6m
Was this helpful?

Key Concepts

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

Enzyme Activity and Temperature

Enzymes, including pepsin, are proteins that catalyze biochemical reactions. Their activity is highly dependent on temperature; generally, as temperature increases, enzyme activity rises due to increased molecular movement. However, extreme temperatures can denature enzymes, leading to a loss of function. At low temperatures, such as 0 °C, enzyme activity is significantly reduced because molecular interactions slow down, resulting in fewer effective collisions between the enzyme and substrate.
Recommended video:
Guided course
1:31
Factors Affecting Enzyme Activity Example 1

pH and Enzyme Function

Enzymes have optimal pH ranges where they function most effectively. Pepsin, for instance, operates best in the highly acidic environment of the stomach (pH 1.5 to 2.0). Deviations from this optimal pH can lead to decreased enzyme activity or denaturation. At a neutral or basic pH, pepsin's structure may be altered, impairing its ability to hydrolyze peptide bonds efficiently.
Recommended video:
Guided course
02:16
Logarithmic Functions

Reaction Rate and Substrate Concentration

The rate of an enzyme-catalyzed reaction is influenced by substrate concentration. Initially, as substrate concentration increases, the reaction rate also increases, as more substrate molecules are available for the enzyme to act upon. However, this relationship only holds until the enzyme becomes saturated; beyond this point, additional substrate does not increase the reaction rate. At low temperatures, the reduced kinetic energy can further limit the effective concentration of substrate molecules interacting with the enzyme.
Recommended video:
Guided course
02:16
Rate of Reaction Concept 7
Related Practice
Textbook Question

How does an irreversible inhibitor function differently than a reversible inhibitor?

Textbook Question

Problems 10.94 and 10.95 both mention enzymes that hydrolyze peptide bonds. How do you account for the fact that pepsin has a high catalytic activity at pH 1.5 but chymotrypsin has very little activity at pH 1.5?

Textbook Question

If each of the following amino acid side chains is present in the active site of an enzyme, indicate whether it would (a) serve a catalytic function, (b) serve to hold the substrate, or (c) both.

d. lysine

Textbook Question

If each of the following amino acid side chains is present in the active site of an enzyme, indicate whether it would (a) serve a catalytic function, (b) serve to hold the substrate, or (c) both.

a. aspartate

Textbook Question

Pepsin, an enzyme that hydrolyzes peptide bonds in proteins, functions in the stomach at a pH optimum of 1.5 to 2.0. How is the rate of a pepsin-catalyzed reaction affected by each of the following conditions?

a. increasing the concentration of proteins

Textbook Question

Meats spoil due to the action of enzymes that degrade the proteins. Fresh meats can be preserved for long periods of time by freezing them. Explain how freezing meats works to prevent spoilage.