Podcast
Questions and Answers
Which characteristic is unique to the chemiluminescence method described?
Which characteristic is unique to the chemiluminescence method described?
What role does glutamate oxidase play in the chemiluminescence method?
What role does glutamate oxidase play in the chemiluminescence method?
Which of the following statements about the advantages of the method is NOT true?
Which of the following statements about the advantages of the method is NOT true?
Why should hemolyzed samples be avoided in this assay?
Why should hemolyzed samples be avoided in this assay?
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Which compound at elevated levels can interfere with ALT activity?
Which compound at elevated levels can interfere with ALT activity?
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How does an increase in enzyme concentration affect the rate of a reaction?
How does an increase in enzyme concentration affect the rate of a reaction?
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What is the primary advantage of using a continuous-reading spectrophotometer?
What is the primary advantage of using a continuous-reading spectrophotometer?
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What effect does temperature have on enzyme activity?
What effect does temperature have on enzyme activity?
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At what pH range do most enzyme-catalyzed reactions occur optimally?
At what pH range do most enzyme-catalyzed reactions occur optimally?
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How does extreme pH affect enzymes?
How does extreme pH affect enzymes?
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What defines a multi-enzyme method in a biochemical pathway?
What defines a multi-enzyme method in a biochemical pathway?
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How does measuring absorbance at different intervals benefit linearity assessment?
How does measuring absorbance at different intervals benefit linearity assessment?
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What is the relationship between substrate concentration and reaction rate?
What is the relationship between substrate concentration and reaction rate?
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What factor should be used to correct AST results obtained at 30 degrees Celsius when reporting at 37 degrees Celsius?
What factor should be used to correct AST results obtained at 30 degrees Celsius when reporting at 37 degrees Celsius?
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Which of the following substances does NOT falsely increase AST activity?
Which of the following substances does NOT falsely increase AST activity?
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What volume of Bilirubin Activator is used in each tube?
What volume of Bilirubin Activator is used in each tube?
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What is the reference value for AST at 37 degrees Celsius?
What is the reference value for AST at 37 degrees Celsius?
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How should a sample with AST values greater than 500 IU/L be processed?
How should a sample with AST values greater than 500 IU/L be processed?
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What is the purpose of covering the tubes with parafilm after adding reagents?
What is the purpose of covering the tubes with parafilm after adding reagents?
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What is the wavelength used to zero the spectrophotometer in this procedure?
What is the wavelength used to zero the spectrophotometer in this procedure?
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What effect does chronic alcoholism have on AST activity?
What effect does chronic alcoholism have on AST activity?
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During strenuous exercise, how does AST activity change?
During strenuous exercise, how does AST activity change?
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How long should the samples stand at room temperature after mixing?
How long should the samples stand at room temperature after mixing?
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Which of these factors contributes to a 5-10% variation in AST levels?
Which of these factors contributes to a 5-10% variation in AST levels?
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Which component is not included in the patient sample tube?
Which component is not included in the patient sample tube?
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What is the detection limit for the AST reagent?
What is the detection limit for the AST reagent?
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What does the calculation of concentration of the unknown require?
What does the calculation of concentration of the unknown require?
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What is the total volume of reagents required for the control sample?
What is the total volume of reagents required for the control sample?
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What are the reference values for Total Bilirubin at birth?
What are the reference values for Total Bilirubin at birth?
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How does muscle mass influence creatinine kinase activity between males and females?
How does muscle mass influence creatinine kinase activity between males and females?
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What is the effect of competitive inhibition on Km when an inhibitor is present?
What is the effect of competitive inhibition on Km when an inhibitor is present?
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How does the presence of noncompetitive inhibition affect Vmax?
How does the presence of noncompetitive inhibition affect Vmax?
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What physiological factor contributes to the differences in alcohol metabolism between males and females?
What physiological factor contributes to the differences in alcohol metabolism between males and females?
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In which scenario would creatinine kinase levels likely be higher?
In which scenario would creatinine kinase levels likely be higher?
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What happens to Km and Vmax in the presence of uncompetitive inhibition?
What happens to Km and Vmax in the presence of uncompetitive inhibition?
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What is a characteristic of lower creatinine kinase levels found in a population?
What is a characteristic of lower creatinine kinase levels found in a population?
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Which demographic might exhibit higher creatinine kinase levels due to muscle mass characteristics?
Which demographic might exhibit higher creatinine kinase levels due to muscle mass characteristics?
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Study Notes
Enzyme Activity Factors
- Enzyme Concentration: Higher enzyme levels accelerate reactions due to increased availability for substrate interaction.
- Temperature Impact: For every 10°C increase, enzyme activity doubles, enhancing molecular movement and reaction speed.
- pH Levels: Optimal activity occurs between pH 7.0-8.0; extreme pH can denature enzymes or alter amino acid states, affecting active sites.
Multi-Enzyme Methods
- Enzymes work sequentially in biochemical pathways; the product of one reaction acts as the substrate for the next.
- Measuring the final target substrate indicates the overall efficiency of the pathway.
Serum Bilirubin Determination Experiment Steps
- Label test tubes for Reagent Blank, Standard, Patient Sample, and Control.
- Add specified volumes of Total Bilirubin Reagent, Bilirubin Activator, and corresponding samples, then mix.
- Let the mixture stand for 90 seconds before zeroing the spectrophotometer and measuring absorbance at 540 nm.
Calculation and Reference Values
- Total Bilirubin Calculation: Uses absorbance values of unknown relative to the standard.
- Reference values at birth: up to 5 mg/dL and up to 85.5 μmol/L.
Influence of Inhibitors on Enzyme Kinetics
- Competitive Inhibition: Increases Km, Vmax remains unchanged.
- Noncompetitive Inhibition: Reduces both Km and Vmax.
- Uncompetitive Inhibition: Km unchanged, Vmax reduced.
Factors Affecting AST Activity
- Elevated AST levels can result from various conditions including lipemic samples, high pyruvate levels, anabolic steroids, and chronic alcoholism.
- Exercise: Strenuous physical activity can significantly increase AST levels.
Temperature Correction
- For reactions performed at different temperatures, apply correction factors (e.g., multiply by 1.43 for results at 30°C to report at 37°C).
Detection Limits and Sample Considerations
- Reagents have a linear detection limit up to 500 IU/L; samples exceeding should be diluted and results adjusted accordingly.
- Serum is preferred for testing but plasma may be acceptable; avoid hemolyzed samples as they affect results.
Advantages of Kinetic Methods
- Kinetic assays, especially those using spectrophotometry, provide more accurate assessment of enzymatic reactions compared to colorimetric methods.
- Allows for continuous monitoring improving the accuracy of linearity assessments across reactions.
Interfering Substances
- Pyridoxal phosphate can artificially elevate ALT values by stimulating apoenzyme activation.
- High levels of pyruvate (> 0.2 mmol/L) can similarly interfere with results.
Specimen Considerations
- Serum is ideal; plasma may be used but must be free of hemolysis to ensure reliable activity measurement.
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Description
This quiz explores the relationship between enzyme concentration and the rate of biochemical reactions. Understand the impact of higher enzyme levels on reaction speed and the advantages of continuous measurement techniques. Perfect for students studying biochemistry concepts.