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.
Q: What does Km describe in terms of enzyme active sites?
A: Km describes the substrate concentration at which half of the enzyme’s active sites are occupied by the substrate.
Q: What does Vmax represent?
A: Vmax represents the maximum reaction velocity, indicating how fast the reaction can occur under ideal conditions.
Q: What does Vmax reveal about an enzyme?
A: Vmax reveals the turnover number of an enzyme, which is the number of substrate molecules catalyzed per second by each enzyme molecule.
Q: Why are enzymes important for biological processes?
A: Enzymes catalyze biological reactions by reducing the activation energy needed for the reactions to occur. They bind to specific substrates, speed up the reaction, and are released unchanged to be used again.
Q: Why is enzyme activity regulation important?
A: Enzyme activity needs to be tightly regulated to maintain homeostasis within the body.
