37 Questions
What is the primary function of enzymes in biological systems?
Acting as catalysts for chemical reactions
Which of the following is true about most enzymes?
They are globular proteins
What is the purpose of enzyme inhibition?
To prevent enzyme catalysis
What is the key role of enzyme co-factors?
Direct participation in catalytic reactions
How do enzymes interact with their substrates?
By creating high-energy intermediates
What do Michaelis-Menten and Lineweaver-Burk Plots describe?
The rate of enzyme-catalyzed reactions
Which enzyme has the highest turnover number?
Carbonic anhydrase
What type of inhibition occurs when the inhibitor binds with the enzyme at a site which is distinct from the substrate binding site?
Non-competitive inhibition
In which type of inhibition is there no change in the Vmax for the reaction?
Competitive inhibition
Which type of inhibition decreases both the apparent KM and Vmax for the reaction?
Uncompetitive inhibition
What is a measure of the affinity of an inhibitor drug for an enzyme?
Inhibitor constant (Ki)
Which enzyme drug targets hypertension?
Angiotensin Converting Enzyme (ACE)
What is the main mechanism of action for statins in treating cardiovascular disease?
Inhibition of HMG CoA reductase
Which enzyme is targeted by NSAIDs like aspirin and ibuprofen?
Cyclooxygenase 2 (COX 2)
What happens to the Vmax for the reaction in non-competitive inhibition?
Unchanged
What is the suffix commonly added to the names of enzymes?
-ase
Which of the following is NOT a main class of enzymes based on the type of reaction they catalyze?
Synthetases
What is the function of a prosthetic group in relation to enzymes?
It provides structural support to the enzyme.
Which of the following is an example of a cofactor for enzymes?
NAD (niacin)
What is the name for the complete, catalytically active enzyme together with its bound cofactor and/or metal ion?
Holoenzyme
Which type of metabolic reactions involve the formation of bonds between molecules and require more energy than they produce?
Anabolic reactions
What role do enzymes play in cellular metabolic reactions?
Decreasing activation energy
What is the main function of enzymes in metabolic reactions?
To lower the activation energy of the reaction
How do enzymes accelerate the rate of a reaction?
By binding to and forming an intermediate with the substrate
Which model of enzyme action involves a conformational change in the enzyme due to substrate binding?
Induced-Fit Model
What factor affects enzyme function by altering the charges on the enzyme and substrate molecules?
pH
What is the effect of increasing enzyme concentration on reaction rate?
It increases until all active sites become engaged, then levels off
What happens to enzyme activity when the temperature exceeds the optimum level?
It decreases due to denaturation of enzymes
What is the main effect of increasing substrate concentration on reaction rate?
It increases until all enzyme active sites become engaged, then levels off
What is the pH range in which pepsin functions as a digestive enzyme?
pH 2-3
How does extreme pH affect enzymes?
It leads to denaturation and loss of substrate fit
What disrupts the attraction between charged amino acids in enzymes?
Extreme salinity
What is enzyme kinetics?
The study of chemical reactions catalyzed by enzymes
Who proposed the Michaelis-Menten Kinetics model?
Michaelis and Menten
What is the 'saturation effect' exhibited by all enzymes with their substrates?
At low substrate concentrations, the reaction rate is proportional to substrate concentration
What determines the rate of formation of the enzyme-substrate complex in the Michaelis-Menten Kinetics model?
Rate constant k1
What does the Michaelis-Menten Equation (Vmax = [S][E]/KM) describe?
The relationship between reaction velocity and substrate concentration
Study Notes
- Pepsin and trypsin are two different digestive enzymes with extreme pH optima: pepsin functions in the stomach at pH 2-3, while trypsin operates in the small intestines at pH 8.
- Extreme pH levels can lead to enzyme denaturation, disrupting the attraction between charged amino acids and distorting the enzyme's 3D structure, resulting in loss of substrate fit.
- Enzymes are intolerant of extreme salinity, which disrupts attraction between charged amino acids, affects 2° and 3° enzyme structure, and ultimately disrupts bonds and the enzyme's 3D shape, leading to decreased reaction rate.
- Enzyme kinetics is the study of the rates of chemical reactions catalyzed by enzymes and provides insight into enzyme catalysis, their role in metabolism, the mechanisms of enzyme inhibition, and the mechanisms of metabolic control.
- In 1913, Michaelis and Menten proposed the Michaelis-Menten Kinetics model, which describes how enzymes increase the rate of metabolic reactions and how reaction rates depend on the concentration of enzyme and substrate.
- All enzymes exhibit a 'saturation effect' with their substrates, which means that at low substrate concentrations, the reaction rate is proportional to substrate concentration. However, as substrate concentration increases, the reaction rate no longer remains proportional and eventually becomes constant and independent of substrate concentration.
- Michaelis and Menten proposed a scheme for a saturating enzyme-catalyzed single substrate reaction, where the free enzyme binds its substrate to form an enzyme-substrate complex, which either undergoes further transformation to yield a final product or breaks down to reform the free enzyme and substrate.
- The rate of formation of the enzyme-substrate complex is determined by the rate constant, k1, while the rate of breakdown of the complex is determined by the rate constant, k-1, and the rate constant, k2.
- By applying the equilibrium constant equation and rearranging, the Michaelis-Menten equation (Vmax = [S][E]/KM) was derived, which describes the relationship between reaction velocity and substrate concentration.
- Michaelis and Menten derived the Michaelis-Menten Equation from the Michaelis-Menten Kinetics model.
- Michaelis-Menten Kinetics can be represented graphically using Lineweaver-Burk Plot and Eadie-Hofstee Plot for determining the kinetic parameters, including Vmax and KM.
- KM (Michaelis Constant) is a key parameter in Michaelis-Menten Kinetics, which has the same unit as the substrate, represents the substrate concentration at which the reaction velocity is 50% of the maximum velocity (Vmax), and indicates the enzyme's affinity for its substrate.
- KM values vary for different enzymes, with lower values indicating a higher affinity for the substrate, while higher values indicate a lower affinity for the substrate.
- Vmax is the maximum velocity or rate of reaction, giving an idea of how fast the reaction can occur under ideal circumstances and revealing the turnover number of an enzyme.
Test your knowledge about enzymes and their role as catalysts in speeding up biochemical reactions, providing alternative pathways, and lowering activation energy. This quiz covers the mechanisms of enzyme action and their impact on reaction rates and equilibrium.
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