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Questions and Answers
What condition can lead to increased levels of alkaline phosphatase in the blood?
What condition can lead to increased levels of alkaline phosphatase in the blood?
Which enzyme is primarily associated with liver function and is measured in U/L?
Which enzyme is primarily associated with liver function and is measured in U/L?
Which of the following enzyme levels would likely indicate liver damage?
Which of the following enzyme levels would likely indicate liver damage?
What could potentially cause elevated gamma glutamyl transferase levels?
What could potentially cause elevated gamma glutamyl transferase levels?
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Which based on the reference range, indicates a high level of creatinine?
Which based on the reference range, indicates a high level of creatinine?
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In the context of enzyme induction, which scenario would most likely lead to increased enzyme levels?
In the context of enzyme induction, which scenario would most likely lead to increased enzyme levels?
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Which enzyme would be elevated following myocardial infarction?
Which enzyme would be elevated following myocardial infarction?
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What is the reference range for normal levels of potassium in MEQ/L?
What is the reference range for normal levels of potassium in MEQ/L?
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What typically happens to enzymes when cell membranes are damaged?
What typically happens to enzymes when cell membranes are damaged?
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Which of the following statements is true regarding the presence of enzymes in the blood?
Which of the following statements is true regarding the presence of enzymes in the blood?
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What is the role of anticoagulants in the preparation of plasma?
What is the role of anticoagulants in the preparation of plasma?
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How is serum obtained from a blood sample?
How is serum obtained from a blood sample?
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What can cause an increase in the levels of diagnostic enzymes in the blood?
What can cause an increase in the levels of diagnostic enzymes in the blood?
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Which of the following is false regarding enzyme activity measurement?
Which of the following is false regarding enzyme activity measurement?
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What is one of the primary functions of enzymes in cells?
What is one of the primary functions of enzymes in cells?
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Why is serum preferred over plasma for certain laboratory assays?
Why is serum preferred over plasma for certain laboratory assays?
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What percentage of normal, healthy individuals will give results within 1 standard deviation of the mean in a Gaussian distribution?
What percentage of normal, healthy individuals will give results within 1 standard deviation of the mean in a Gaussian distribution?
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Which of the following describes how reference ranges are typically established for Gaussian distributions?
Which of the following describes how reference ranges are typically established for Gaussian distributions?
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What is the danger level for cholesterol values according to the provided information?
What is the danger level for cholesterol values according to the provided information?
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Which method is used to determine reference limits when test results are skewed?
Which method is used to determine reference limits when test results are skewed?
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At what fasting glucose level is impaired fasting glucose or pre-diabetes indicated?
At what fasting glucose level is impaired fasting glucose or pre-diabetes indicated?
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What does critical difference refer to in the context of laboratory tests?
What does critical difference refer to in the context of laboratory tests?
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Which factors may produce unwanted effects on enzyme activity?
Which factors may produce unwanted effects on enzyme activity?
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Which of the following is true regarding isoenzymes?
Which of the following is true regarding isoenzymes?
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What role do subunits play in lactate dehydrogenase?
What role do subunits play in lactate dehydrogenase?
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How is the amount of enzyme in a patient's sample typically determined?
How is the amount of enzyme in a patient's sample typically determined?
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What is the primary advantage of measuring enzyme levels immunologically?
What is the primary advantage of measuring enzyme levels immunologically?
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In electrophoretic separation, at what pH do most proteins migrate toward the positive pole?
In electrophoretic separation, at what pH do most proteins migrate toward the positive pole?
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Which enzymatic isoenzymes can be distinguished using immunological assays?
Which enzymatic isoenzymes can be distinguished using immunological assays?
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What defines the differences in the proportions of lactate dehydrogenase isozymes in various tissues?
What defines the differences in the proportions of lactate dehydrogenase isozymes in various tissues?
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Which lactate dehydrogenase isozyme has the highest proportion of M subunits?
Which lactate dehydrogenase isozyme has the highest proportion of M subunits?
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In which time frame does CK-MB peak after a myocardial infarction?
In which time frame does CK-MB peak after a myocardial infarction?
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How does the presence of enzyme affect reaction velocity in an enzyme activity assay?
How does the presence of enzyme affect reaction velocity in an enzyme activity assay?
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What can be inferred about LD-1 based on its timing related to myocardial infarction?
What can be inferred about LD-1 based on its timing related to myocardial infarction?
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Which protein has the longest duration before returning to normal after elevation?
Which protein has the longest duration before returning to normal after elevation?
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What aspect of creatine kinase influences its activity?
What aspect of creatine kinase influences its activity?
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Which of the following is the molecular weight of Troponin T?
Which of the following is the molecular weight of Troponin T?
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Study Notes
Diagnostic Use of Enzymes
- Most enzymes have intracellular functions and are not normally present in blood.
- Damage to cell structures can release intracellular enzymes into bodily fluids.
- Enzyme activity can be measured in serum, the fluid obtained from blood after clotting.
- Increased blood plasma enzyme levels can indicate:
- Cell membrane injury
- Enzyme induction
- Tumor presence
- Cell proliferation
- Common examples of enzymes used in diagnostics include:
- Alkaline phosphatase (ALP or ALK): found in liver, bone, and other tissues.
- Gamma glutamyl transferase (GGT or GGTP): found in liver and pancreas
-
Transaminases:
- Alanine aminotransferase (ALT or SGPT): found in liver.
- Aspartate aminotransferase (AST or SGOT): found in liver, muscle.
- Lactate dehydrogenase (LDH or LD): found in liver, muscle, red blood cells.
- Creatine kinase (CK or CPK): found in muscle.
Laboratory Test Results and Interpretation
-
Gaussian distribution: most laboratory test results for healthy populations follow a bell-shaped curve with:
- 67% of results within 1 standard deviation of the mean.
- 95% of results within 2 standard deviations of the mean.
- 99.7% of results within 3 standard deviations of the mean.
- Skewed distributions: some tests may have skewed distributions where reference ranges are established by dropping the top and bottom 2.5% of results.
- Critical difference: the difference between serial test results that must occur before significance can be claimed.
Isoenzymes
- Isoenzymes are different forms of the same enzyme with varying physical properties but the same catalytic function.
- They can be found in different tissues, organisms, or even different cells within the same tissue.
Lactate Dehydrogenase
- LDH is a tetramer composed of two subunit types (H and M).
- Five possible isoenzyme combinations exist: LDH1 (HHHH), LDH2 (HHHM), LDH3 (HHMM), LDH4 (HMMM), LDH5 (MMMM).
- Tissue-specific expression of H and M subunits results in varying amounts of each isoenzyme in different tissues.
- Elevated LDH1 may indicate a myocardial infarction.
- Elevated LDH5 may indicate liver disease.
Creatine Kinase
- CK exists as a dimer with two types of subunits: B and M.
- Three possible isoenzyme combinations exist: CK1 (BB), CK2 (MB), CK3 (MM).
- CK-MB is specific to heart muscle.
- Elevated CK-MB may indicate a myocardial infarction.
Protein Markers of Myocardial Infarction
- Different protein markers can indicate a myocardial infarction, each with a specific time frame for detection:
- Myoglobin: Initial elevation 2-4 hours, peak 6-9 hours, returns to normal 24-36 hours.
- CK-MB: Initial elevation 6-10 hours, peak 18-24 hours, returns to normal 1-3 days.
- Troponin I: Initial elevation 3-12 hours, peak 18-24 hours, returns to normal 5-9 days.
- Troponin T: Initial elevation 3-12 hours, peak 18-24 hours, returns to normal by 14 days.
- LDH-1: Initial elevation 12-24 hours, peak 36-40 hours, returns to normal 5-14 days.
Enzyme Activity Assays
- Enzyme activity is measured by quantifying the formation of reaction products over time.
- Samples are compared to known enzyme concentrations to determine the amount of enzyme present.
- Enzyme activity can be affected by factors such as pH, temperature, cofactors, and inhibitors.
Enzyme Immunoassays
- Immune assays utilize antibodies that bind to specific enzymes.
- Labeled antibodies allow for quantification of the enzyme present.
- Immunological assays measure the amount of enzyme regardless of functionality.
Electrophoretic Separation
- Electrophoresis separates charged particles based on their mobility in an electric field.
- isoenzymes with different charges can be separated using this technique.
- Isoenzymes are separated based on their migration patterns towards the positive electrode.
Clinical Significance of Isoenzyme Analysis
- By analyzing isoenzyme patterns, we can identify the tissue of origin for enzyme leakage, aiding in diagnosis.
- For example:
- Elevated CK-MB suggests heart muscle damage.
- Elevated LDH1 suggests heart muscle damage and may also be present with liver or red blood cell damage.
- Monitoring changes in isoenzyme levels over time can provide insight into disease progression and treatment effectiveness.
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Description
Explore the diagnostic use of enzymes in medical tests. This quiz covers how intracellular enzymes are released into bodily fluids and the significance of various enzyme levels in detecting injuries, tumors, and other health conditions. Key enzymes such as ALP, GGT, ALT, and others are highlighted.
