Week 14 / Enzymes 2 Flashcards
Q: How does pH affect enzyme function?
A: Changes in pH can add or remove H+ ions, altering the charges on the enzyme and substrate molecules, which affects the binding of the substrate to the enzyme’s active site.
Q: What happens to enzymes at extreme salinity?
A: Extreme salinity can cause enzyme denaturation by disrupting bonds and altering the enzyme’s 3D shape, affecting its secondary (2°) and tertiary (3°) structure.
Q: What is the optimum pH for enzyme-catalyzed reactions?
A: The optimum pH is the pH at which the enzyme functions best. For most human enzymes, it is pH 6-8, but it depends on the enzyme’s localized environment (e.g., pepsin works at pH 2-3, trypsin works at pH 8).
Q: What happens when pH levels become extreme?
A: Extreme pH levels can cause enzyme denaturation by disrupting the attraction between charged amino acids, altering the enzyme’s 3D shape, and distorting the active site, leading to a loss of substrate fit.
Q: How does salinity affect enzyme function?
A: Changes in salinity, by adding or removing cations and anions, can disrupt the attraction between charged amino acids, affecting the enzyme’s structure.
Q: What is enzyme kinetics?
A: Enzyme kinetics is the study of the rates of chemical reactions that are catalyzed by enzymes.
Q: Are enzymes tolerant of extreme salinity?
A: No, enzymes are intolerant of extreme salinity, which can lead to a loss of enzyme function.
Q: What insights does enzyme kinetics provide?
A:
Mechanisms of enzyme catalysis and their role in metabolism.
How enzyme activity is controlled in the cell.
How drugs and poisons can inhibit or modulate enzyme activity.
Q: Who proposed the model of enzyme kinetics, and what did it explain?
A: In 1913, Michaelis and Menten proposed the Michaelis-Menten Kinetics model, which explains how enzymes increase the rate of metabolic reactions and how reaction rates depend on the concentrations of enzyme and substrate.
Q: What is the ‘saturation effect’ in enzyme kinetics?
A: The saturation effect occurs when increasing substrate concentration increases the reaction rate until a point where the enzyme becomes saturated with substrate, and further increases in substrate concentration do not affect the reaction rate.
Q: How does reaction rate (V) change at low substrate concentration?
A: At low substrate concentration ([S]), the reaction rate (V) is proportional to the substrate concentration.
Q: How does reaction rate (V) change as substrate concentration increases?
A: As substrate concentration increases, the reaction rate increases, but eventually, it falls off and becomes independent of substrate concentration.
Q: What happens when the enzyme is saturated with substrate?
A: When the enzyme is saturated with substrate, the reaction rate becomes constant and no longer changes with increases in substrate concentration.
Q: What type of graph does the Michaelis-Menten model produce?
A: A plot of initial reaction velocity (V) against substrate concentration ([S]) gives a rectangular hyperbola.
Q: What does the Michaelis-Menten equation explain?
A: The Michaelis-Menten equation explains the ‘saturation effect’ and the relationship between substrate concentration and reaction rate.
Q: What is the Michaelis constant (Km)?
A: Km is the substrate concentration ([S]) at which the reaction proceeds at half maximal velocity (50%).
Q: What does a lower Km value indicate about an enzyme’s affinity for its substrate?
A: The lower the Km value, the higher the enzyme’s affinity for its substrate, meaning the enzyme binds more tightly to the substrate.
Q: What does Km tell us about the strength of the substrate-enzyme binding?
A: Km provides an idea of the strength of binding between the substrate and the enzyme; a lower Km indicates stronger binding.
Q: What does Km indicate about the substrate concentration for enzyme catalysis?
A: Km indicates the lowest substrate concentration ([S]) at which the enzyme can recognize the substrate and begin catalyzing the reaction.
