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.
Q: How is enzyme activity regulated?
A: Regulation is accomplished through enzyme inhibition
Q: How is enzyme inhibition used in clinical therapeutics?
A: Enzyme inhibition is widely exploited in clinical therapeutics to regulate enzyme activity, often in the treatment of diseases.
Q: What are the two main types of enzyme inhibition?
A: The two main types of enzyme inhibition are irreversible and reversible inhibition.
Q: What are the types of reversible inhibition?
A: The types of reversible inhibition are:
Competitive
Non-competitive
Uncompetitive
Mixed
Q: What is competitive inhibition?
A: In competitive inhibition, the inhibitor (I) is structurally similar to the substrate (S) and competes with the substrate for the enzyme’s active site.
Q: How does the inhibitor affect the enzyme-substrate complex in competitive inhibition?
A: The inhibitor has virtually no affinity for the enzyme-substrate complex (ES) because the substrate already occupies the binding site.
Q: What happens to the apparent Km in the presence of a competitive inhibitor?
A: In the presence of a competitive inhibitor, the apparent Km is increased, meaning more substrate is needed to reach half-maximal velocity.
Q: Does competitive inhibition change the Vmax?
A: No, competitive inhibition does not change the Vmax.
Q: How can competitive inhibition be overcome?
A: Competitive inhibition can be reversed by increasing the concentration of the substrate (S).
Q: What is non-competitive inhibition?
A: In non-competitive inhibition, the inhibitor has a similar affinity for both the free enzyme (E) and the enzyme-substrate complex (ES), and it binds to a site distinct from the substrate binding site.
Q: How does the inhibitor affect substrate binding in non-competitive inhibition?
A: The inhibitor binding does not affect the substrate binding, and vice versa.
Q: What happens to the Km in the presence of a non-competitive inhibitor?
A: There is no effect on or change in the Km with non-competitive inhibition.
Q: How does non-competitive inhibition affect the Vmax?
A: Non-competitive inhibition
decreases the Vmax of the reaction, preventing the enzyme from forming its product efficiently.
Q: What is uncompetitive inhibition?
A: In uncompetitive inhibition, the inhibitor has affinity for the enzyme-substrate complex (ES) but not the free enzyme (E).
Q: How does the inhibitor affect the enzyme-substrate complex in uncompetitive inhibition?
A: The inhibitor binds only to the enzyme-substrate complex (ES), forming an inactive ESI complex, which does not produce the product (P).
Q: What happens to the Km in the presence of an uncompetitive inhibitor?
A: The apparent Km is decreased because the inhibitor selectively binds to the enzyme-substrate complex (ES).
Q: How does uncompetitive inhibition affect the Vmax?
A: The Vmax for the reaction is decreased because the enzyme-substrate complex is prevented from producing the product.
Q: Can uncompetitive inhibition be reversed by increasing substrate concentration?
A: No, inhibition cannot be reversed by increasing the substrate concentration.
Q: How does competitive inhibition affect the apparent Km and Vmax?
A: In competitive inhibition, the apparent Km is increased, while the Vmax remains unchanged.
Q: How does non-competitive inhibition affect the apparent Km and Vmax?
A: In non-competitive inhibition, the apparent Km remains unchanged, while the Vmax is decreased.
Q: How does uncompetitive inhibition affect the apparent Km and Vmax?
A: In uncompetitive inhibition, the apparent Km is decreased, and the Vmax is also decreased.
Q: What does the inhibitor constant (Ki) measure?
A: The inhibitor constant (Ki) measures the affinity of an inhibitor drug for an enzyme.
Q: How are Ki values used in relation to enzyme inhibitors?
A: Ki values are used to characterize and compare the effectiveness of inhibitors relative to Km, helping to evaluate their potential therapeutic value for a given enzyme reaction.
Q: What does a lower Ki value indicate?
A: A lower Ki value indicates tighter binding between the inhibitor and the enzyme, making the inhibitor more effective.
