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Questions and Answers
What function does a Transferase enzyme perform?
What function does a Transferase enzyme perform?
Which enzyme is classified as a ligase?
Which enzyme is classified as a ligase?
What is the primary role of oxidative enzymes like lactate dehydrogenase?
What is the primary role of oxidative enzymes like lactate dehydrogenase?
What is a characteristic of stereoisomers targeted by isozymes?
What is a characteristic of stereoisomers targeted by isozymes?
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Which of the following statements about enzyme nomenclature is correct?
Which of the following statements about enzyme nomenclature is correct?
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What distinguishes kinases within the Enzyme Commission numerical nomenclature?
What distinguishes kinases within the Enzyme Commission numerical nomenclature?
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Which of the following enzyme functions is associated with hydrolases?
Which of the following enzyme functions is associated with hydrolases?
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In the Enzyme Commission numerical designation, what do the first and second numbers represent?
In the Enzyme Commission numerical designation, what do the first and second numbers represent?
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What type of reaction do lyases catalyze?
What type of reaction do lyases catalyze?
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Which of the following is a characteristic of enzymes?
Which of the following is a characteristic of enzymes?
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Which of the following enzymes serves as an example of an aminotransferase?
Which of the following enzymes serves as an example of an aminotransferase?
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What is the role of capital letter abbreviations for enzyme names?
What is the role of capital letter abbreviations for enzyme names?
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Which of the following statements is false regarding deaminases?
Which of the following statements is false regarding deaminases?
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What happens to an enzyme when it exceeds its optimum temperature?
What happens to an enzyme when it exceeds its optimum temperature?
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What defines the optimum temperature for an enzyme?
What defines the optimum temperature for an enzyme?
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Which statement about enzymes and thermophilic bacteria is correct?
Which statement about enzymes and thermophilic bacteria is correct?
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What role does a coenzyme play in enzyme activity?
What role does a coenzyme play in enzyme activity?
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How does an increase in temperature initially affect enzyme activity?
How does an increase in temperature initially affect enzyme activity?
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What characteristic differentiates the type of amylase that cannot be detected in certain conditions?
What characteristic differentiates the type of amylase that cannot be detected in certain conditions?
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Which statement best describes the peak time for lipase levels in the context of biliary tract disease?
Which statement best describes the peak time for lipase levels in the context of biliary tract disease?
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Which of the following is NOT a type of cardiovascular disease mentioned?
Which of the following is NOT a type of cardiovascular disease mentioned?
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What is the primary function of lactate dehydrogenase (LDH) as described?
What is the primary function of lactate dehydrogenase (LDH) as described?
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Which coenzyme is involved with lactate dehydrogenase during its enzymatic action?
Which coenzyme is involved with lactate dehydrogenase during its enzymatic action?
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What is the primary function of AST in the body?
What is the primary function of AST in the body?
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Which liver enzymes are primarily used to assess liver injury?
Which liver enzymes are primarily used to assess liver injury?
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In which tissues is AST distributed?
In which tissues is AST distributed?
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Which of the following best defines a competitive inhibitor?
Which of the following best defines a competitive inhibitor?
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What is the reference value range for AST in IU/L?
What is the reference value range for AST in IU/L?
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What happens in uncompetitive inhibition?
What happens in uncompetitive inhibition?
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What type of liver enzyme is defined as those used to assess biliary obstruction?
What type of liver enzyme is defined as those used to assess biliary obstruction?
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Which product is produced by the reaction catalyzed by AST?
Which product is produced by the reaction catalyzed by AST?
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What distinguishes stable angina from unstable angina?
What distinguishes stable angina from unstable angina?
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Which of the following symptoms is NOT typically associated with angina pectoris?
Which of the following symptoms is NOT typically associated with angina pectoris?
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What is a common characteristic of unstable angina?
What is a common characteristic of unstable angina?
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What is the preferred pH range for the reference method measuring enzymatic activity?
What is the preferred pH range for the reference method measuring enzymatic activity?
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What effect does adding a-hydroxyurea have on LD4 and LD5 samples?
What effect does adding a-hydroxyurea have on LD4 and LD5 samples?
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What type of chest pain typically indicates stable angina?
What type of chest pain typically indicates stable angina?
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Which method is most commonly used for measuring lactate dehydrogenase activity?
Which method is most commonly used for measuring lactate dehydrogenase activity?
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Which of the following statements about unstable angina is true?
Which of the following statements about unstable angina is true?
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Study Notes
Clinical Enzymology
- Apoenzyme: The protein portion of an enzyme without its cofactor.
- Activator: A molecule that increases an enzyme's activity by binding to it. Can be organic (like NAD/NADH) or inorganic (electrolyte).
- Inhibitor: A substance that reduces the rate of enzymatic reactions. It binds to the active site or allosteric site.
- Active site: The region where a substrate binds to an enzyme.
- Allosteric site: A different region of an enzyme other than the active site where regulatory molecules bind.
- Catalytic activity: An enzyme's ability to speed up biochemical reactions.
- Coenzyme: A low molecular weight, diffusible, heat-stable substance that combines with an inactive protein (apoenzyme) to form an active compound (holoenzyme).
- Enzyme: A protein molecule that accelerates chemical reactions without being consumed itself. Specific for a substrate. Large molecules typically located inside cells. They're released into the blood after cellular injury and degradation.
- Isoenzyme: Related enzymes that catalyze the same reaction, but with different structures and physical, biochemical, and immunological properties.
- International unit (IU): A standard unit of enzyme measurement. Also expressed as Katal.
- Substrate: A reactant in a biochemical reaction.
- Product: A substance produced by an enzyme-catalyzed reaction.
Enzyme Theories
- Emil Fischer's "Lock and Key" Theory: Enzymes have rigid active sites, and the substrate shape must precisely fit.
- Koshland's "Induced Fit" Theory: Enzymes have flexible active sites that adjust their shape to accommodate the substrate.
Enzyme Kinetics
- Activation energy: The minimum energy needed for a reaction to proceed.
- Transition state: The intermediate stage between substrate and product during a catalyzed reaction.
- Zero-order reaction: Reaction rate depends only on enzyme concentration.
- First-order reaction: Reaction rate is directly proportional to substrate concentration.
Enzyme Specificity
- Absolute specificity: Enzymes combine with only one substrate and catalyze only one reaction.
- Group specificity: Enzymes combine with any substrate within a specific chemical group (e.g., all alcohols).
- Bond specificity: Enzymes react with specific chemical bonds (e.g., ionic, covalent, ester bonds).
Enzyme Classification
- Oxidoreductases: Catalyze oxidation-reduction reactions.
- Transferases: Catalyze the transfer of functional groups.
- Hydrolases: Use water to break down bonds.
- Lyases: Catalyze reactions that remove groups from molecules
- Isomerases: Catalyze structural changes within a molecule.
- Ligases: Combine molecules through bonds.
Enzyme Nomenclature
- Systematic name: Describes the nature of the reaction catalyzed by the enzyme.
- Numerical nomenclature: Associated with a unique numerical code (EC).
Enzyme Activity Measurement
- Fixed-time (Endpoint) Method: Measures the concentration of products at a specific time point during a reaction
- Continuous Monitoring (Kinetic Assay): Measures reaction rate during the reaction, providing ongoing measurements of product formation or substrate consumption.
Units for Enzyme Activity
- International Unit (IU): Amount of enzyme that catalyzes 1 micromole of substrate per minute.
- Katal (kat): Amount of enzyme that catalyzes 1 mole of substrate per second.
Liver Enzymes and Liver Function Tests
- AST (Aspartate aminotransferase): Enzyme found in various tissues, including the liver and heart. Elevated levels can indicate liver damage.
- ALT (Alanine aminotransferase): Primarily found in the liver. Elevated levels strongly suggest liver injury.
- Other liver specific markers: These other enzymes can be associated with obstructive jaundice.
Cardiac Markers
- Troponin I and T: Highly specific markers for myocardial damage. Elevated levels indicate a heart attack.
- Creatine kinase (CK): Enzyme released from damaged muscle cells, especially the heart, but widely distributed in tissues.
- Lactate dehydrogenase (LD): Enzyme found in many tissues, including the heart. Elevated levels can indicate heart attack or other conditions.
- Other markers: Myoglobin, H-FABP, IMA (Ischemia-Modified Albumin) may have uses in cardiac diagnosis.
Alkaline Phosphatase (ALP)
- Hydrolase (EC 3.1.3.1): Enzyme involved in the hydrolysis of phosphate monoesters, mainly in the liver, bone, and intestine.
- Clinical Significance: Elevated levels may suggest skeletal, liver or intestinal conditions, such as obstructive jaundice or bone diseases.
Acid Phosphatase (ACP)
- Hydrolase (EC 3.1.3.2): Enzyme that hydrolyzes phosphate groups from organic phosphate compounds, found typically in various tissues and cells.
- Clinical Significance: Elevated levels may be associated with certain cancers and other illnesses.
Other Clinically Significant Enzymes
- Amylase: Enzyme that breaks down carbohydrates (starch, glycogen); elevated levels can suggest pancreatitis (inflammation of the pancreas).
- Lipase: Enzyme that breaks down lipids; elevated levels are highly specific for pancreatic damage.
- Gamma-glutamyl transferase (GGT): Enzyme indicating liver damage or blockage of bile ducts; useful in monitoring chronic alcohol use.
- Glucose-6-Phosphate Dehydrogenase (G6PD): Enzyme important for protecting red blood cells from oxidative stress.
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Description
Test your knowledge on clinical enzymology concepts, including the roles of apoenzymes, activators, inhibitors, and the active site of enzymes. This quiz covers important definitions and functions that are critical in biochemistry and medicine. Challenge yourself with questions related to enzymatic reactions and their regulation.
