Podcast
Questions and Answers
Which characteristic is most responsible for the specificity of an enzyme?
Which characteristic is most responsible for the specificity of an enzyme?
- The unique shape of its active site (correct)
- The speed at which it can catalyze reactions
- Its ability to be regulated by feedback inhibition
- Its requirement for cofactors
Enzymes are able to catalyze a wide array of reactions, regardless of the substrate.
Enzymes are able to catalyze a wide array of reactions, regardless of the substrate.
False (B)
Name the process where enzymes break down complex food molecules into simpler ones for absorption.
Name the process where enzymes break down complex food molecules into simpler ones for absorption.
Digestion
Enzymes are essential for the production of energy through pathways like glycolysis, the citric acid cycle, and oxidative ______.
Enzymes are essential for the production of energy through pathways like glycolysis, the citric acid cycle, and oxidative ______.
Match each process with the type of enzyme primarily involved:
Match each process with the type of enzyme primarily involved:
What role do enzymes play in metabolic pathways?
What role do enzymes play in metabolic pathways?
Enzymes are only involved in breaking down molecules and not in building complex molecules.
Enzymes are only involved in breaking down molecules and not in building complex molecules.
Name the bodily process by which enzymes help to neutralize harmful substances.
Name the bodily process by which enzymes help to neutralize harmful substances.
Enzymes facilitate communication between cells through their involvement in cell ______ pathways.
Enzymes facilitate communication between cells through their involvement in cell ______ pathways.
In which of the following biological processes are enzymes NOT directly involved?
In which of the following biological processes are enzymes NOT directly involved?
In Michaelis-Menten kinetics, what does a low Km value indicate?
In Michaelis-Menten kinetics, what does a low Km value indicate?
In competitive inhibition, Vmax remains the same, while Km increases.
In competitive inhibition, Vmax remains the same, while Km increases.
What type of enzyme inhibition is characterized by the inhibitor binding only to the enzyme-substrate complex?
What type of enzyme inhibition is characterized by the inhibitor binding only to the enzyme-substrate complex?
In a Lineweaver-Burk plot, the x-intercept represents _______.
In a Lineweaver-Burk plot, the x-intercept represents _______.
Match the type of enzyme catalysis with its description:
Match the type of enzyme catalysis with its description:
Which type of enzyme inhibition results in parallel lines on a Lineweaver-Burk plot?
Which type of enzyme inhibition results in parallel lines on a Lineweaver-Burk plot?
Non-competitive inhibitors affect Km but do not affect Vmax.
Non-competitive inhibitors affect Km but do not affect Vmax.
What is the role of cofactors and coenzymes in enzyme activity?
What is the role of cofactors and coenzymes in enzyme activity?
___________ regulation involves modulators binding to regulatory sites on an enzyme, affecting its activity.
___________ regulation involves modulators binding to regulatory sites on an enzyme, affecting its activity.
How does feedback inhibition regulate metabolic pathways?
How does feedback inhibition regulate metabolic pathways?
Which of the following enzyme classes is responsible for catalyzing oxidation-reduction reactions?
Which of the following enzyme classes is responsible for catalyzing oxidation-reduction reactions?
Ligases catalyze the cleavage of bonds by the addition of water.
Ligases catalyze the cleavage of bonds by the addition of water.
What type of reaction do transferases catalyze?
What type of reaction do transferases catalyze?
_________ catalyze the rearrangement of atoms within a molecule.
_________ catalyze the rearrangement of atoms within a molecule.
Match each enzyme class with its corresponding reaction type:
Match each enzyme class with its corresponding reaction type:
Which enzyme class would be utilized to join two large molecules, such as DNA fragments, together?
Which enzyme class would be utilized to join two large molecules, such as DNA fragments, together?
Oxidoreductases are involved in reactions that only involve the addition of oxygen.
Oxidoreductases are involved in reactions that only involve the addition of oxygen.
Describe the general function of lyases in biochemical reactions.
Describe the general function of lyases in biochemical reactions.
In a reaction where a phosphate group is moved from ATP to glucose, the enzyme involved would be classified as a _________.
In a reaction where a phosphate group is moved from ATP to glucose, the enzyme involved would be classified as a _________.
Which of the following is NOT a characteristic reaction catalyzed by hydrolases?
Which of the following is NOT a characteristic reaction catalyzed by hydrolases?
How do enzymes affect the activation energy of a reaction?
How do enzymes affect the activation energy of a reaction?
Enzymes are consumed during the reactions they catalyze.
Enzymes are consumed during the reactions they catalyze.
The location on an enzyme where the substrate binds is called the ______ site.
The location on an enzyme where the substrate binds is called the ______ site.
Which of the following is NOT a common mechanism by which enzymes lower activation energy?
Which of the following is NOT a common mechanism by which enzymes lower activation energy?
Describe the relationship between an enzyme, its substrate, and the enzyme-substrate complex.
Describe the relationship between an enzyme, its substrate, and the enzyme-substrate complex.
Which of the following is true regarding the specificity of enzymes?
Which of the following is true regarding the specificity of enzymes?
Increasing the concentration of an enzyme will not affect the rate of reaction, assuming the substrate is in excess.
Increasing the concentration of an enzyme will not affect the rate of reaction, assuming the substrate is in excess.
What is the transition state in an enzyme-catalyzed reaction?
What is the transition state in an enzyme-catalyzed reaction?
Match the following terms with their correct description:
Match the following terms with their correct description:
Explain how an enzyme's structure is directly related to its function in catalyzing reactions.
Explain how an enzyme's structure is directly related to its function in catalyzing reactions.
Which statement accurately describes the relationship between an apoenzyme, cofactor, and holoenzyme?
Which statement accurately describes the relationship between an apoenzyme, cofactor, and holoenzyme?
A prosthetic group is a cofactor that is loosely bound to the enzyme and easily dissociates during purification.
A prosthetic group is a cofactor that is loosely bound to the enzyme and easily dissociates during purification.
What is the primary role of the apoenzyme component within a holoenzyme structure?
What is the primary role of the apoenzyme component within a holoenzyme structure?
A __________ is the catalytically active enzyme complex formed by the binding of an apoenzyme and its cofactor.
A __________ is the catalytically active enzyme complex formed by the binding of an apoenzyme and its cofactor.
Match each prosthetic group with its associated function:
Match each prosthetic group with its associated function:
Which characteristic distinguishes prosthetic groups from other types of cofactors?
Which characteristic distinguishes prosthetic groups from other types of cofactors?
An apoenzyme can efficiently catalyze reactions without its associated cofactor.
An apoenzyme can efficiently catalyze reactions without its associated cofactor.
What determines the specificity of an enzyme for its substrate?
What determines the specificity of an enzyme for its substrate?
__________ are non-protein chemical compounds required for the biological activity of certain enzymes.
__________ are non-protein chemical compounds required for the biological activity of certain enzymes.
Which of the following is an example of a prosthetic group involved in oxygen transport?
Which of the following is an example of a prosthetic group involved in oxygen transport?
Which of the following best describes a cofactor?
Which of the following best describes a cofactor?
A coenzyme is a protein that enhances the rate of a reaction.
A coenzyme is a protein that enhances the rate of a reaction.
Explain the role of a metalloenzyme in a biological system. Give an example.
Explain the role of a metalloenzyme in a biological system. Give an example.
A vitamin-derived organic molecule that assists in enzymatic reactions is known as a(n) ________.
A vitamin-derived organic molecule that assists in enzymatic reactions is known as a(n) ________.
Match the following enzymes/cofactors with their respective functions or characteristics:
Match the following enzymes/cofactors with their respective functions or characteristics:
Which of the following is NOT a typical function of cofactors?
Which of the following is NOT a typical function of cofactors?
All enzymes require a cofactor to function.
All enzymes require a cofactor to function.
What distinguishes a metalloenzyme from other types of enzymes?
What distinguishes a metalloenzyme from other types of enzymes?
Describe how a deficiency in a specific vitamin could affect enzyme activity in the human body.
Describe how a deficiency in a specific vitamin could affect enzyme activity in the human body.
An enzyme without its required cofactor is called a(n) ________, while the complete, active enzyme-cofactor complex is called a(n) ________.
An enzyme without its required cofactor is called a(n) ________, while the complete, active enzyme-cofactor complex is called a(n) ________.
Which of the following is a characteristic of a first-order reaction?
Which of the following is a characteristic of a first-order reaction?
For a zero-order reaction, changing the reactant concentration will double the reaction rate.
For a zero-order reaction, changing the reactant concentration will double the reaction rate.
Write the integrated rate law for a first-order reaction, defining all terms used.
Write the integrated rate law for a first-order reaction, defining all terms used.
In a zero-order reaction, the plot of reactant concentration versus time is ________ with a slope of ________.
In a zero-order reaction, the plot of reactant concentration versus time is ________ with a slope of ________.
Match the reaction order with its corresponding half-life characteristic:
Match the reaction order with its corresponding half-life characteristic:
Which of the following reactions is an example of a zero-order reaction?
Which of the following reactions is an example of a zero-order reaction?
If a reaction's rate doubles when the concentration of a reactant is doubled, the reaction is first-order with respect to that reactant.
If a reaction's rate doubles when the concentration of a reactant is doubled, the reaction is first-order with respect to that reactant.
What does the rate constant (k) represent in the rate law for both zero-order and first-order reactions, and how do their units differ?
What does the rate constant (k) represent in the rate law for both zero-order and first-order reactions, and how do their units differ?
The half-life (t1/2) of a first-order reaction is calculated using the formula t1/2 = ________, where k is the rate constant.
The half-life (t1/2) of a first-order reaction is calculated using the formula t1/2 = ________, where k is the rate constant.
For a zero-order reaction with a rate constant k and an initial concentration $[A]_0$, what is the concentration of $A$ after a time interval equal to two half-lives?
For a zero-order reaction with a rate constant k and an initial concentration $[A]_0$, what is the concentration of $A$ after a time interval equal to two half-lives?
Which of the following best describes an apoenzyme?
Which of the following best describes an apoenzyme?
A prosthetic group dissociates from the enzyme between catalytic cycles.
A prosthetic group dissociates from the enzyme between catalytic cycles.
What distinguishes a prosthetic group from other types of cofactors?
What distinguishes a prosthetic group from other types of cofactors?
A holoenzyme is formed when an apoenzyme binds with its necessary ______.
A holoenzyme is formed when an apoenzyme binds with its necessary ______.
Match the enzyme component with its description:
Match the enzyme component with its description:
Which form of an enzyme is catalytically active?
Which form of an enzyme is catalytically active?
If an enzyme requires a metal ion for its activity, what is the protein part of the enzyme called before the metal ion binds?
If an enzyme requires a metal ion for its activity, what is the protein part of the enzyme called before the metal ion binds?
An apoenzyme can catalyze biochemical reactions without its required cofactor(s).
An apoenzyme can catalyze biochemical reactions without its required cofactor(s).
Provide an example of an organic prosthetic group.
Provide an example of an organic prosthetic group.
The binding of a cofactor to an apoenzyme is typically ______ and specific.
The binding of a cofactor to an apoenzyme is typically ______ and specific.
Which of the following is the primary role of a cofactor in an enzyme-catalyzed reaction?
Which of the following is the primary role of a cofactor in an enzyme-catalyzed reaction?
A coenzyme is a type of cofactor that is typically a metal ion or cluster.
A coenzyme is a type of cofactor that is typically a metal ion or cluster.
Briefly explain how the absence of a required metalloenzyme impacts an organism's metabolism.
Briefly explain how the absence of a required metalloenzyme impacts an organism's metabolism.
Apoenzymes are inactive without the addition of a(n) ___________, which completes the active holoenzyme form.
Apoenzymes are inactive without the addition of a(n) ___________, which completes the active holoenzyme form.
Match the following enzymes with their respective cofactors:
Match the following enzymes with their respective cofactors:
Which of the following best describes how coenzymes participate in enzymatic reactions?
Which of the following best describes how coenzymes participate in enzymatic reactions?
All cofactors are permanently bound to their respective enzymes.
All cofactors are permanently bound to their respective enzymes.
How can the concentration of specific metal ions in an organism's environment impact the effectiveness of metalloenzymes?
How can the concentration of specific metal ions in an organism's environment impact the effectiveness of metalloenzymes?
Flavin adenine dinucleotide (FAD), which is derived from vitamin B2, serves as a(n) ___________ in various redox reactions.
Flavin adenine dinucleotide (FAD), which is derived from vitamin B2, serves as a(n) ___________ in various redox reactions.
Identify which statement correctly describes the action of cofactors.
Identify which statement correctly describes the action of cofactors.
Which CK isoenzyme is most specific to cardiac tissue and is often the primary marker for myocardial infarction?
Which CK isoenzyme is most specific to cardiac tissue and is often the primary marker for myocardial infarction?
An elevated CK-BB level in serum is commonly associated with myocardial infarction.
An elevated CK-BB level in serum is commonly associated with myocardial infarction.
Describe the dimeric composition of the CK-MM isoenzyme and its primary tissue source.
Describe the dimeric composition of the CK-MM isoenzyme and its primary tissue source.
The CK isoenzyme predominant in brain tissue is _______.
The CK isoenzyme predominant in brain tissue is _______.
Match each CK isoenzyme with its primary tissue source:
Match each CK isoenzyme with its primary tissue source:
Which condition, other than myocardial infarction, can significantly elevate CK-MB levels due to skeletal muscle involvement?
Which condition, other than myocardial infarction, can significantly elevate CK-MB levels due to skeletal muscle involvement?
The presence of CK-Mt in serum is a routine diagnostic test for assessing tissue damage.
The presence of CK-Mt in serum is a routine diagnostic test for assessing tissue damage.
Why is it important to consider other clinical findings and markers in conjunction with CK-MB levels when diagnosing a myocardial infarction?
Why is it important to consider other clinical findings and markers in conjunction with CK-MB levels when diagnosing a myocardial infarction?
What is the dimeric composition of CK-MB?
What is the dimeric composition of CK-MB?
Elevated levels of CK-BB may indicate damage to the _______, but are not specific and require further investigation.
Elevated levels of CK-BB may indicate damage to the _______, but are not specific and require further investigation.
Which CK isoenzyme is predominantly found in skeletal muscle?
Which CK isoenzyme is predominantly found in skeletal muscle?
In a healthy individual, CK-MB is typically the most abundant CK isoenzyme in serum.
In a healthy individual, CK-MB is typically the most abundant CK isoenzyme in serum.
Following a myocardial infarction (MI), which CK isoenzyme rises and falls most rapidly?
Following a myocardial infarction (MI), which CK isoenzyme rises and falls most rapidly?
The CK isoenzyme primarily associated with brain tissue is ______.
The CK isoenzyme primarily associated with brain tissue is ______.
Which of the following CK isoenzyme patterns is most indicative of a myocardial infarction in the days following the event?
Which of the following CK isoenzyme patterns is most indicative of a myocardial infarction in the days following the event?
In a patient presenting with chest pain, a normal CK-MB level 12 hours after the onset of pain would suggest:
In a patient presenting with chest pain, a normal CK-MB level 12 hours after the onset of pain would suggest:
Elevated CK-BB levels are commonly used as a primary diagnostic marker for myocardial infarction.
Elevated CK-BB levels are commonly used as a primary diagnostic marker for myocardial infarction.
Besides myocardial infarction, what other condition might cause an elevation in CK-MB levels?
Besides myocardial infarction, what other condition might cause an elevation in CK-MB levels?
If a patient has elevated total CK but normal CK isoenzyme levels, it suggests:
If a patient has elevated total CK but normal CK isoenzyme levels, it suggests:
Which of the following methods separates CK isoenzymes based on their electrical charge?
Which of the following methods separates CK isoenzymes based on their electrical charge?
Immunoinhibition directly measures the enzymatic activity of both CK-MB and CK-MM isoenzymes simultaneously.
Immunoinhibition directly measures the enzymatic activity of both CK-MB and CK-MM isoenzymes simultaneously.
What principle does electrophoresis use to separate CK isoenzymes?
What principle does electrophoresis use to separate CK isoenzymes?
In immunoinhibition, antibodies are used to ______ the activity of certain CK isoenzymes.
In immunoinhibition, antibodies are used to ______ the activity of certain CK isoenzymes.
Which CK isoenzyme method involves the use of antibodies to block the activity of one or more isoenzymes?
Which CK isoenzyme method involves the use of antibodies to block the activity of one or more isoenzymes?
Electrophoresis is solely used for CK isoenzymes and cannot be applied to other types of proteins or enzymes.
Electrophoresis is solely used for CK isoenzymes and cannot be applied to other types of proteins or enzymes.
In the context of CK isoenzyme analysis, what is the purpose of inhibiting one isoenzyme when using immunoinhibition?
In the context of CK isoenzyme analysis, what is the purpose of inhibiting one isoenzyme when using immunoinhibition?
The rate of migration of CK isoenzymes during electrophoresis depends on their charge and ______.
The rate of migration of CK isoenzymes during electrophoresis depends on their charge and ______.
Which method would be most suitable for quantifying CK-MB activity in the presence of a high concentration of CK-MM?
Which method would be most suitable for quantifying CK-MB activity in the presence of a high concentration of CK-MM?
Match the following CK isoenzyme procedures with their respective principles:
Match the following CK isoenzyme procedures with their respective principles:
Which liver enzyme is more specific to liver damage, as opposed to damage in other organs such as the heart or muscles?
Which liver enzyme is more specific to liver damage, as opposed to damage in other organs such as the heart or muscles?
Elevated levels of Alkaline Phosphatase (ALP) exclusively indicate liver disease.
Elevated levels of Alkaline Phosphatase (ALP) exclusively indicate liver disease.
Briefly describe the enzymatic reaction catalyzed by Alanine Aminotransferase (ALT).
Briefly describe the enzymatic reaction catalyzed by Alanine Aminotransferase (ALT).
An AST/ALT ratio greater than 2 is suggestive of ______ liver disease.
An AST/ALT ratio greater than 2 is suggestive of ______ liver disease.
Match the liver enzyme with its primary clinical significance:
Match the liver enzyme with its primary clinical significance:
Which of the following methodologies is commonly used to measure AST and ALT activity in a clinical laboratory?
Which of the following methodologies is commonly used to measure AST and ALT activity in a clinical laboratory?
Reference ranges for liver enzymes are consistent across all laboratories and patient populations.
Reference ranges for liver enzymes are consistent across all laboratories and patient populations.
Explain how cholestasis affects Alkaline Phosphatase (ALP) levels.
Explain how cholestasis affects Alkaline Phosphatase (ALP) levels.
Elevated levels of AST and ALT in conjunction with elevated bilirubin and prolonged prothrombin time suggest ______ liver damage.
Elevated levels of AST and ALT in conjunction with elevated bilirubin and prolonged prothrombin time suggest ______ liver damage.
Why are liver enzyme tests like AST, ALT, and ALP essential in clinical practice?
Why are liver enzyme tests like AST, ALT, and ALP essential in clinical practice?
Which of the following statements accurately describes the tetrameric composition of lactate dehydrogenase (LDH) isoenzymes?
Which of the following statements accurately describes the tetrameric composition of lactate dehydrogenase (LDH) isoenzymes?
Match the LDH isoenzyme with its predominant tissue location:
Match the LDH isoenzyme with its predominant tissue location:
LDH5 is primarily found in high concentrations in cardiac muscle due to its optimal function in aerobic conditions.
LDH5 is primarily found in high concentrations in cardiac muscle due to its optimal function in aerobic conditions.
Which LDH isoenzyme is most likely to be elevated in a patient presenting with acute myocardial infarction?
Which LDH isoenzyme is most likely to be elevated in a patient presenting with acute myocardial infarction?
If a patient's blood work reveals a significant elevation in LDH5, which organ systems should be further investigated?
If a patient's blood work reveals a significant elevation in LDH5, which organ systems should be further investigated?
The isoenzyme LDH______ is typically found in the highest concentration in heart tissue, while LDH5 is abundant in ______ and ______.
The isoenzyme LDH______ is typically found in the highest concentration in heart tissue, while LDH5 is abundant in ______ and ______.
How does the relative proportion of M and H subunits influence the functional properties of LDH isoenzymes?
How does the relative proportion of M and H subunits influence the functional properties of LDH isoenzymes?
The different LDH isoenzymes catalyze different reactions. LDH1 catalyzes the oxidation of lactate, while LDH5 exclusively catalyzes the reverse reaction.
The different LDH isoenzymes catalyze different reactions. LDH1 catalyzes the oxidation of lactate, while LDH5 exclusively catalyzes the reverse reaction.
A clinician observes elevated levels of both LDH1 and LDH2 in a patient's serum. Considering the overlap in tissue distribution, what could this indicate?
A clinician observes elevated levels of both LDH1 and LDH2 in a patient's serum. Considering the overlap in tissue distribution, what could this indicate?
Why is it clinically relevant to differentiate between the various LDH isoenzymes in serum samples?
Why is it clinically relevant to differentiate between the various LDH isoenzymes in serum samples?
Gamma-glutamyl transferase (GGT) catalyzes the transfer of a gamma-glutamyl group to which of the following?
Gamma-glutamyl transferase (GGT) catalyzes the transfer of a gamma-glutamyl group to which of the following?
Elevated 5'-nucleotidase (5'-NT) levels are highly specific to bone disorders compared to GGT which is more specific to liver disorders.
Elevated 5'-nucleotidase (5'-NT) levels are highly specific to bone disorders compared to GGT which is more specific to liver disorders.
Briefly describe how GGT levels are clinically significant in differentiating between hepatic and non-hepatic causes of elevated alkaline phosphatase (ALP).
Briefly describe how GGT levels are clinically significant in differentiating between hepatic and non-hepatic causes of elevated alkaline phosphatase (ALP).
The Szasz method for measuring GGT utilizes the substrate L-gamma-glutamyl-p-nitroanilide, which upon reaction releases __________, a yellow-colored compound that is measured spectrophotometrically.
The Szasz method for measuring GGT utilizes the substrate L-gamma-glutamyl-p-nitroanilide, which upon reaction releases __________, a yellow-colored compound that is measured spectrophotometrically.
Which of the following conditions is MOST likely to cause a disproportionately high elevation in GGT compared to other liver enzymes like ALT and AST?
Which of the following conditions is MOST likely to cause a disproportionately high elevation in GGT compared to other liver enzymes like ALT and AST?
Reference ranges for GGT and 5'-NT are consistent across all laboratories and are not affected by age or sex.
Reference ranges for GGT and 5'-NT are consistent across all laboratories and are not affected by age or sex.
Explain the principle behind the clinical use of 5'-NT in confirming hepatobiliary disease.
Explain the principle behind the clinical use of 5'-NT in confirming hepatobiliary disease.
The Bowers and McComb method, commonly used for measuring 5'-NT activity, involves the hydrolysis of ____________ to adenosine, which is then converted to inosine and ammonia.
The Bowers and McComb method, commonly used for measuring 5'-NT activity, involves the hydrolysis of ____________ to adenosine, which is then converted to inosine and ammonia.
A patient presents with elevated alkaline phosphatase (ALP) and normal GGT. Which of the following is the MOST likely cause of the elevated ALP?
A patient presents with elevated alkaline phosphatase (ALP) and normal GGT. Which of the following is the MOST likely cause of the elevated ALP?
Match the enzyme with its clinical significance:
Match the enzyme with its clinical significance:
Which enzyme primarily catalyzes the breakdown of starch and glycogen?
Which enzyme primarily catalyzes the breakdown of starch and glycogen?
Elevated levels of lipase are exclusively indicative of pancreatic disorders.
Elevated levels of lipase are exclusively indicative of pancreatic disorders.
What is the primary clinical significance of measuring amylase and lipase levels in serum?
What is the primary clinical significance of measuring amylase and lipase levels in serum?
The enzyme ________ is crucial for the digestion of fats in the small intestine.
The enzyme ________ is crucial for the digestion of fats in the small intestine.
Match each enzyme with its respective primary substrate:
Match each enzyme with its respective primary substrate:
Which methodologies are commonly used to measure amylase activity in a clinical laboratory?
Which methodologies are commonly used to measure amylase activity in a clinical laboratory?
Trypsin and chymotrypsin are primarily involved in the breakdown of carbohydrates.
Trypsin and chymotrypsin are primarily involved in the breakdown of carbohydrates.
Briefly describe the clinical significance of trypsinogen in serum.
Briefly describe the clinical significance of trypsinogen in serum.
Reference ranges for pancreatic enzymes are typically expressed in units per liter (U/L) and can vary based on ________.
Reference ranges for pancreatic enzymes are typically expressed in units per liter (U/L) and can vary based on ________.
Which condition is MOST likely indicated by significantly elevated levels of both amylase and lipase?
Which condition is MOST likely indicated by significantly elevated levels of both amylase and lipase?
Acid phosphatase (ACP) activity is often measured in forensic medicine to detect:
Acid phosphatase (ACP) activity is often measured in forensic medicine to detect:
Aldolase (ALD) catalyzes a reaction important in gluconeogenesis but not glycolysis.
Aldolase (ALD) catalyzes a reaction important in gluconeogenesis but not glycolysis.
What substrate is commonly used in the clinical assay for cholinesterase (CHE) activity?
What substrate is commonly used in the clinical assay for cholinesterase (CHE) activity?
In the liver, aldolase B (ALD-B) cleaves fructose-1-phosphate into glyceraldehyde and ______.
In the liver, aldolase B (ALD-B) cleaves fructose-1-phosphate into glyceraldehyde and ______.
Match each enzyme with its primary clinical significance.
Match each enzyme with its primary clinical significance.
Which of the following conditions would most likely show decreased levels of serum cholinesterase (CHE)?
Which of the following conditions would most likely show decreased levels of serum cholinesterase (CHE)?
The reference range for acid phosphatase (ACP) is the same for all age groups.
The reference range for acid phosphatase (ACP) is the same for all age groups.
Which method is most commonly used to measure aldolase (ALD) activity in a clinical laboratory?
Which method is most commonly used to measure aldolase (ALD) activity in a clinical laboratory?
Exposure to what type of substances will affect CHE levels in the body?
Exposure to what type of substances will affect CHE levels in the body?
The primary activator for aldolase (ALD) enzyme activity is ______.
The primary activator for aldolase (ALD) enzyme activity is ______.
Flashcards
Enzymes
Enzymes
Biological molecules, mainly proteins, that accelerate chemical reactions within cells.
Catalysis
Catalysis
The main function of enzymes, they speed up chemical reactions.
Specificity
Specificity
Enzymes only catalyze a single reaction, or a set of closely related reactions.
Regulation
Regulation
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Digestion
Digestion
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Energy Production
Energy Production
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Synthesis
Synthesis
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Detoxification
Detoxification
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Cell signaling
Cell signaling
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DNA Replication and Repair
DNA Replication and Repair
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Enzyme Definition
Enzyme Definition
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Vmax
Vmax
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Km (Michaelis Constant)
Km (Michaelis Constant)
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Lineweaver-Burk Plot
Lineweaver-Burk Plot
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Competitive Inhibition
Competitive Inhibition
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Uncompetitive Inhibition
Uncompetitive Inhibition
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Non-competitive Inhibition
Non-competitive Inhibition
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Lowering Activation Energy
Lowering Activation Energy
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Proximity and Orientation Effects
Proximity and Orientation Effects
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Feedback Inhibition
Feedback Inhibition
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Oxidoreductases Enzymes
Oxidoreductases Enzymes
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Transferases Enzymes
Transferases Enzymes
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Hydrolases Enzymes
Hydrolases Enzymes
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Lyases Enzymes
Lyases Enzymes
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Isomerases Enzymes
Isomerases Enzymes
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Ligases Enzymes
Ligases Enzymes
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Activation Energy
Activation Energy
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Active Site
Active Site
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Substrate
Substrate
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Enzyme-Substrate Complex
Enzyme-Substrate Complex
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Enzyme Catalysis
Enzyme Catalysis
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Apoenzyme
Apoenzyme
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Cofactor
Cofactor
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Prosthetic Group
Prosthetic Group
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Holoenzyme
Holoenzyme
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Heme
Heme
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Biotin
Biotin
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Flavin Nucleotides (FAD/FMN)
Flavin Nucleotides (FAD/FMN)
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Metalloenzyme
Metalloenzyme
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Chemical Kinetics
Chemical Kinetics
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Reaction Order
Reaction Order
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First-Order Reactions
First-Order Reactions
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Half-Life (t1/2)
Half-Life (t1/2)
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Integrated Rate Law
Integrated Rate Law
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Zero-Order Reactions
Zero-Order Reactions
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Zero-Order Half-life equation
Zero-Order Half-life equation
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Zero-Order Integrated Rate Law
Zero-Order Integrated Rate Law
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Apoenzyme's state
Apoenzyme's state
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Binding of Prosthetic Group
Binding of Prosthetic Group
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Holoenzyme's function
Holoenzyme's function
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CK-MM (CK3)
CK-MM (CK3)
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CK-MB (CK2)
CK-MB (CK2)
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CK-BB (CK1)
CK-BB (CK1)
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CK-MM composition
CK-MM composition
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CK-MB composition
CK-MB composition
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CK-BB composition
CK-BB composition
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Normal CK Isoenzyme Pattern
Normal CK Isoenzyme Pattern
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CK Pattern After MI
CK Pattern After MI
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Electrophoresis (CK Isoenzymes)
Electrophoresis (CK Isoenzymes)
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Immunoinhibition (CK Isoenzymes)
Immunoinhibition (CK Isoenzymes)
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Aspartate Aminotransferase (AST)
Aspartate Aminotransferase (AST)
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Alanine Aminotransferase (ALT)
Alanine Aminotransferase (ALT)
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Alkaline Phosphatase (ALP)
Alkaline Phosphatase (ALP)
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AST, ALT and ALP Methodologies
AST, ALT and ALP Methodologies
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Elevated Liver Enzymes Significance
Elevated Liver Enzymes Significance
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LD Isoenzymes
LD Isoenzymes
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Clinical Significance (LD)
Clinical Significance (LD)
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Gamma-Glutamyl Transferase (GGT)
Gamma-Glutamyl Transferase (GGT)
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5'-Nucleotidase (5'-NT)
5'-Nucleotidase (5'-NT)
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GGT and 5'-NT Methodologies
GGT and 5'-NT Methodologies
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Amylase (AMY)
Amylase (AMY)
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Lipase (LPS)
Lipase (LPS)
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Trypsin (TRY)
Trypsin (TRY)
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Chymotrypsin (CHY)
Chymotrypsin (CHY)
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Acid Phosphatase (ACP)
Acid Phosphatase (ACP)
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Aldolase (ALD)
Aldolase (ALD)
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Cholinesterase (CHE)
Cholinesterase (CHE)
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Study Notes
- Enzymes are biological molecules, primarily proteins, that significantly speed up the rate of virtually all of the chemical reactions that take place within cells without being consumed themselves
- Essential for life and serve a wide range of important functions in the body
- Enzyme-catalyzed reactions follow specific mechanisms
- Some enzymes need non-protein components (organic or inorganic) to function correctly
- Chemical kinetics studies reaction rates and factors influencing them
- Reaction order indicates how reactant concentration affects reaction rate
- Apoenzyme, prosthetic groups, and holoenzyme are terms associated with enzymes
- Many enzymes require additional non-protein components called cofactors to carry out their catalytic activity
- Cofactors can be metal ions or organic molecules
- Apoenzyme, prosthetic groups, and holoenzyme describe the state of an enzyme concerning the presence or absence of its necessary cofactors
General Functions of Enzymes
- Catalysis: The primary and most well-known function of enzymes is to act as catalysts
- Specificity: Enzymes are highly specific; each enzyme typically catalyzes a single reaction or a set of closely related reactions
- Regulation: Enzymes are involved in regulatory pathways, controlling metabolic flux and maintaining homeostasis
- Digestion: Enzymes play a crucial role in digestion, breaking down complex food molecules into simpler ones that the body can absorb
- Energy Production: Enzymes are essential for energy production pathways like glycolysis, the citric acid cycle, and oxidative phosphorylation
- Synthesis: Enzymes are responsible for synthesizing complex molecules from simpler precursors
- Detoxification: Enzymes play a critical role in detoxifying harmful substances in the body
- Cell Signaling: Enzymes are involved in cell signaling pathways, transmitting signals and coordinating cellular responses
- Muscle Contraction: Enzymes are involved in muscle contraction
- Nerve Function: Enzymes are critical for nerve function
- Blood Clotting: Enzymes are involved in the blood clotting cascade
- DNA Replication and Repair: Enzymes are essential for DNA replication, repair, and maintenance of genomic integrity
- Cell Growth and Differentiation: Enzymes play roles in cell growth, differentiation, and development
Apoenzyme
- Refers to the protein part of an enzyme that is inactive on its own
- Requires a cofactor to become catalytically active
- The apoenzyme provides the specific binding site for the substrate and the cofactor
- Without the cofactor, the apoenzyme cannot properly catalyze a reaction
- The apoenzyme establishes the specificity of the enzyme for its substrate
- Refers to an enzyme that requires a cofactor but does not have one bound
- It is the protein part of an enzyme without its prosthetic group(s) or cofactor(s)
- Inactive and cannot catalyze a biochemical reaction without its required cofactor(s)
- Becomes catalytically active once the necessary cofactor(s) bind to it
- The binding of the cofactor to the apoenzyme is specific and usually involves non-covalent interactions
- Some enzymes may require more than one cofactor to be catalytically active
- Example: In enzymes that require a metal ion for activity, the protein without the metal ion is the apoenzyme
Cofactors
- Cofactors are non-protein chemical compounds required for the biological activity of some specific enzymes
- Examples: Metal ions, such as Mg2+, Zn2+, or organic molecules
Coenzymes
- Coenzymes are organic non-protein molecules that help enzymes carry out catalysis
- Many coenzymes are derived from vitamins
- Examples: NAD+, FAD, coenzyme A
Metalloenzymes
- Metalloenzymes are enzymes that contain one or more metal ions that are essential for their catalytic activity
- The metal ion is tightly bound to the enzyme
- Examples: Cytochrome oxidase (containing copper and iron), superoxide dismutase (containing zinc and copper), and catalase (containing iron)
Prosthetic Groups
- Prosthetic groups are cofactors that are tightly or covalently bound to the enzyme protein
- They are a specific type of cofactor that is essential for the enzyme's function
- Because they are tightly bound, they remain associated with the enzyme even through purification processes
- Examples:
- Heme in hemoglobin and cytochromes: Heme is an iron-containing porphyrin ring essential for oxygen transport (hemoglobin) and electron transfer (cytochromes)
- Biotin in carboxylases: Biotin is a vitamin that serves as a carrier of carbon dioxide in carboxylation reactions
- Flavin nucleotides (FAD/FMN) in flavoproteins: FAD and FMN are derived from riboflavin (vitamin B2) and are involved in redox reactions
- The key characteristic of prosthetic groups is their permanent or very stable association with the enzyme
- Tightly or covalently bound to an enzyme
- Essential for the enzyme's function
- A specific type of cofactor
- Remains permanently associated with the enzyme, even between catalytic cycles
- Can be organic molecules or metal ions
- Organic prosthetic groups include heme in hemoglobin and flavin adenine dinucleotide (FAD) in flavoproteins
- Metal ion examples include iron-sulfur clusters in enzymes involved in electron transfer
- Tight binding distinguishes prosthetic groups from other cofactors (coenzymes) that bind transiently
Holoenzyme
- Holoenzyme is the catalytically active enzyme complex
- Consists of the apoenzyme and its required cofactor(s)
- It is formed when the cofactor binds to the apoenzyme, resulting in a functional enzyme
- Holoenzyme = Apoenzyme + Cofactor
- Only the holoenzyme form can efficiently bind substrate and catalyze the reaction
- The formation of a holoenzyme is essential for the enzyme to perform its biological function
- Refers to the catalytically active enzyme complex, which includes both the enzyme (apoenzyme) and its necessary cofactor(s)
- Consists of the apoenzyme plus the prosthetic group(s) or coenzyme(s)
- The complete and functional enzyme unit
- Only the holoenzyme form of an enzyme can catalyze biochemical reactions
- The formation of a holoenzyme from an apoenzyme and its cofactor(s) involves the correct binding and positioning of the cofactor within the enzyme's active site
- Example: An enzyme like cytochrome oxidase, which requires both a protein component and heme as a cofactor, is only active when both are present, forming the holoenzyme
Michaelis-Menten Kinetics
- Describes the rate of enzymatic reactions, relating reaction rate (V) to the concentration of substrate ([S])
- The Michaelis-Menten equation is: V = (Vmax [S]) / (Km + [S])
- V is the reaction velocity
- Vmax is the maximum reaction velocity when the enzyme is saturated with substrate
- [S] is the substrate concentration
- Km is the Michaelis constant, representing the substrate concentration at which the reaction rate is half of Vmax
- Km indicates the affinity of the enzyme for the substrate
- A low Km indicates high affinity, meaning the enzyme reaches Vmax at a lower substrate concentration
- A high Km indicates low affinity, meaning a higher substrate concentration is needed to reach Vmax
Lineweaver-Burk Plot
- Also known as the double reciprocal plot
- It is a graphical representation of the Michaelis-Menten equation
- Useful for determining Km and Vmax, and also for analyzing enzyme inhibition
- The Lineweaver-Burk equation is: 1/V = (Km/Vmax) (1/[S]) + 1/Vmax
- The plot of 1/V versus 1/[S] yields a straight line
- The y-intercept is 1/Vmax
- The x-intercept is -1/Km
- The slope is Km/Vmax
Enzyme Inhibition
- Enzyme inhibitors reduce the rate of enzyme-catalyzed reactions
- There are several types of enzyme inhibition such as: competitive, uncompetitive, non-competitive, and mixed inhibition
Competitive Inhibition
- The inhibitor binds to the active site of the enzyme
- It prevents the substrate from binding
- Competitive inhibition increases Km, but does not affect Vmax
- The enzyme can still reach Vmax if there is enough substrate to outcompete the inhibitor
- In Lineweaver-Burk plot, competitive inhibition is indicated by the same y-intercept (Vmax is unchanged) but a different x-intercept (Km is increased)
Uncompetitive Inhibition
- The inhibitor binds only to the enzyme-substrate complex
- Prevents the complex from proceeding to form products
- Uncompetitive inhibition decreases both Km and Vmax
- In Lineweaver-Burk plot, uncompetitive inhibition is indicated by parallel lines, showing both Km and Vmax are decreased
Non-competitive Inhibition
- The inhibitor binds to both the enzyme and the enzyme-substrate complex
- It binds at a site distinct from the active site
- Non-competitive inhibition decreases Vmax, but does not affect Km
- The enzyme's efficiency is reduced, regardless of substrate concentration
- In Lineweaver-Burk plot, noncompetitive inhibition is indicated by the same x-intercept (Km is unchanged) but a different y-intercept (Vmax is decreased)
Mixed Inhibition
- The inhibitor can bind to both the enzyme alone and the enzyme-substrate complex
- Affects both Km and Vmax, but to different extents
- If the inhibitor binds the enzyme with equal affinity whether or not the substrate is bound, it is called non-competitive
- In Lineweaver-Burk plot, mixed inhibition is indicated by lines that intersect, but not on either axis
Enzyme Catalysis Mechanism
- Enzymes enhance reaction rates by lowering the activation energy (Ea)
- Activation energy is the energy required to reach the transition state
- Enzymes provide an alternative reaction pathway with a lower Ea
- Enzymes achieve this through several mechanisms
Proximity and Orientation Effects
- Enzymes bring substrates into close proximity
- They orients them correctly for the reaction
- Increases the frequency of effective collisions
Acid-Base Catalysis
- Enzymes use acidic or basic amino acid residues in the active site
- Transfer protons to or from the substrate
- Stabilizes transition states
Covalent Catalysis
- The enzyme forms a temporary covalent bond with the substrate
- This creates a new reaction pathway
- It lowers the activation energy
Metal Ion Catalysis
- Metal ions in the active site participate in catalysis
- Act as electrophiles or nucleophiles
- Stabilize charged intermediates
Factors Affecting Enzyme Activity
- Several factors influence the rate of enzyme-catalyzed reactions
Temperature
- Increasing temperature generally increases reaction rate
- Excessive heat can denature the enzyme and abolish activity
- Enzymes have an optimal temperature range
pH
- Enzymes have an optimal pH range
- Extremes of pH can denature the enzyme
- Disrupt ionic and hydrogen bonds that maintain the enzyme's structure
Enzyme Concentration
- Increasing enzyme concentration generally increases reaction rate, assuming substrate is not limiting
- More enzyme molecules are available to catalyze the reaction
Substrate Concentration
- Increasing substrate concentration increases reaction rate
- Up to a point where the enzyme becomes saturated (Vmax)
Cofactors and Coenzymes
- Many enzymes require cofactors or coenzymes for activity
- Cofactors are inorganic ions (e.g., Mg2+, Zn2+)
- Coenzymes are organic molecules (e.g., vitamins)
- They assist in the catalytic mechanism
Enzyme Regulation
- Metabolic pathways are regulated through various mechanisms
- These control enzyme activity
Allosteric Regulation
- Allosteric enzymes have regulatory sites
- Modulators bind to these sites
- Modulators can be activators or inhibitors
- They induce conformational changes that affect enzyme activity
Feedback Inhibition
- The product of a metabolic pathway inhibits an earlier enzyme in the pathway
- It prevents overproduction of the product
Covalent Modification
- Enzymes can be activated or inactivated by covalent modification
- Phosphorylation is a common modification
- Kinases add phosphate groups
- Phosphatases remove phosphate groups
Proteolytic Activation
- Some enzymes are synthesized as inactive precursors (zymogens)
- They are activated by proteolytic cleavage
- Examples include digestive enzymes like trypsin and chymotrypsin
Major Enzyme Groups and Reactions Catalyzed
Oxidoreductases
- Catalyze oxidation-reduction reactions
- Involve the transfer of electrons between molecules
Transferases
- Catalyze the transfer of a functional group from one molecule to another
Hydrolases
- Catalyze the hydrolysis of chemical bonds
- Addition of water
Lyases
- Catalyze the breaking of chemical bonds by means other than hydrolysis and oxidation
Isomerases
- Catalyze the rearrangement of atoms within a molecule
Ligases
- Catalyze the joining of two molecules
- Usually coupled with ATP hydrolysis
First-Order Reactions
- Rate depends linearly on the concentration of one reactant
- Rate Law: rate = k[A], where [A] is the reactant concentration, and k is the rate constant
- Doubling [A] doubles the reaction rate
- Half-life (t1/2) is constant and independent of initial concentration
- Half-life Equation: t1/2 = 0.693 / k
- Integrated Rate Law: ln[A]t - ln[A]0 = -kt, where [A]t is concentration at time t, and [A]0 is initial concentration
- A plot of ln[A] versus time is linear with a slope of -k
- Examples: Radioactive decay; unimolecular isomerization reactions
Zero-Order Reactions
- Rate is independent of reactant concentration
- Rate Law: rate = k, where k is the rate constant
- Changing reactant concentration has no effect on reaction rate
- Rate is constant until the reactant is depleted
- Half-life (t1/2) is directly proportional to initial concentration
- Half-life Equation: t1/2 = [A]0 / 2k
- Integrated Rate Law: [A]t - [A]0 = -kt, where [A]t is concentration at time t, and [A]0 is initial concentration
- A plot of [A] versus time is linear with a slope of -k
- Examples: Reactions catalyzed by surfaces when the surface is saturated; enzymatic reactions when the enzyme is saturated
Creatine Kinase (CK) Isoenzymes - Clinical Significance
- CK isoenzymes are diagnostically important, particularly in assessing tissue damage.
- CK is a dimer, and its isoenzymes are composed of two subunits: M (muscle) and B (brain).
- There are three major CK isoenzymes: CK-MM, CK-MB, and CK-BB.
CK-MM
- Dimeric Composition: Composed of two M subunits (MM).
- Major Sources: Skeletal muscle (primary source) and cardiac muscle.
- Clinical Significance: Elevated levels indicate muscle damage; used in evaluating musculoskeletal disorders and, to a lesser extent, myocardial infarction.
CK-MB
- Dimeric Composition: Composed of one M subunit and one B subunit (MB).
- Major Sources: Primarily cardiac muscle
- Clinical Significance: Elevated levels are a specific and sensitive marker for myocardial infarction (heart attack); used to assess the extent of cardiac damage.
CK-BB
- Dimeric Composition: Composed of two B subunits (BB).
- Major Sources: Brain tissue (primary source), smooth muscle, and some other tissues.
- Clinical Significance: Elevated levels may indicate brain injury or damage; less commonly used compared to CK-MB due to its rapid clearance from serum.
Normal CK Isoenzyme Pattern
- Predominantly CK-MM is found in healthy individuals.
- Small amounts of CK-MB may be present, but CK-BB is typically very low or undetectable.
CK Isoenzyme Pattern Following Myocardial Infarction (MI)
- Initially, total CK levels rise, followed by a rise in CK-MB.
- CK-MB levels typically increase within 4-6 hours after the onset of chest pain.
- CK-MB peaks at around 12-24 hours and returns to normal within 48-72 hours.
- The rise and fall pattern of CK-MB is crucial for diagnosing MI.
- CK-MM levels also increase due to muscle damage, but CK-MB is more specific to cardiac damage.
Other CK Isoenzyme Procedures
- Electrophoresis and Immunoinhibition are alternative methods for CK isoenzyme analysis.
Electrophoresis
- Separates CK isoenzymes based on their electrical charge using an electric field.
- After separation, specific staining is used to visualize and quantify each isoenzyme band.
Immunoinhibition
- Uses antibodies to inhibit the activity of CK-M subunits, allowing for the measurement of CK-B activity.
- By inhibiting CK-M, the remaining activity is primarily due to CK-BB, which can then be quantified.
- This method is particularly useful for detecting CK-BB.
Liver Enzymes: AST, ALT, and ALP
Aspartate Aminotransferase (AST)
- Reaction Catalyzed: AST catalyzes the transfer of an amino group from aspartate to α-ketoglutarate, forming oxaloacetate and glutamate.
- Methodologies: Typically measured using spectrophotometric assays that monitor the rate of NADH oxidation or production, which is coupled to the AST reaction.
- Clinical Significance: Elevated levels indicate liver damage (e.g., hepatitis, cirrhosis) or muscle damage. It's also found in other tissues like heart and kidneys, so it is less specific for liver damage than ALT.
- Reference Range: Varies by laboratory but generally ranges from 5-40 U/L.
Alanine Aminotransferase (ALT)
- Reaction Catalyzed: ALT catalyzes the transfer of an amino group from alanine to α-ketoglutarate, forming pyruvate and glutamate.
- Methodologies: Similar to AST assays, ALT is measured spectrophotometrically by monitoring the rate of NADH oxidation or production, which is coupled to the ALT reaction.
- Clinical Significance: Elevated levels are highly indicative of liver damage. More specific to liver damage than AST, as it is primarily found in the liver. It is used to detect hepatitis, cirrhosis, and other liver disorders.
- Reference Range: Varies by laboratory but generally ranges from 7-56 U/L.
Alkaline Phosphatase (ALP)
- Reaction Catalyzed: ALP catalyzes the hydrolysis of phosphate esters in an alkaline environment.
- Methodologies: ALP activity is usually measured spectrophotometrically by monitoring the hydrolysis of a specific phosphate ester substrate, such as p-nitrophenyl phosphate, at an alkaline pH. The release of p-nitrophenol is measured.
- Clinical Significance: Elevated levels can indicate liver disease (e.g., biliary obstruction, cirrhosis) or bone disorders (e.g., Paget's disease, bone cancer). Additional tests are needed to differentiate between liver and bone sources.
- Reference Range: Varies by laboratory and age, but generally ranges from 30-120 U/L. Higher in children and adolescents due to bone growth.
Lactate Dehydrogenase (LD) Isoenzymes
- LD is a tetrameric enzyme composed of two types of subunits: H (heart) and M (muscle).
- These subunits combine to form five isoenzymes: LD1, LD2, LD3, LD4, and LD5.
LD1
- Tetrameric Composition: HHHH (4H)
- Major Tissue(s): Heart (primary source) and red blood cells.
LD2
- Tetrameric Composition: HHHM (3H1M)
- Major Tissue(s): Heart (also found in red blood cells).
LD3
- Tetrameric Composition: HHMM (2H2M)
- Major Tissue(s): Lung (primary source), spleen, and other tissues.
LD4
- Tetrameric Composition: HMMM (1H3M)
- Major Tissue(s): Liver and muscle.
LD5
- Tetrameric Composition: MMMM (4M)
- Major Tissue(s): Skeletal muscle (primary source) and liver.
Biliary Tract Enzymes: GGT and 5’-NT
Gamma-Glutamyl Transferase (GGT)
- Reaction Catalyzed: GGT catalyzes the transfer of a gamma-glutamyl group from gamma-glutamyl peptides to other amino acids or peptides.
- Methodologies: Commonly measured spectrophotometrically using substrates like γ-glutamyl-p-nitroanilide, where the release of p-nitroanilide is monitored.
- Clinical Significance: Elevated levels are highly indicative of liver and biliary tract diseases (e.g., cholestasis, biliary obstruction). It is also elevated in alcohol-induced liver disease. Very sensitive for detecting biliary obstruction.
- Reference Range: Varies by laboratory but generally ranges from 9-48 U/L.
5’-Nucleotidase (5’-NT)
- Reaction Catalyzed: 5’-NT catalyzes the hydrolysis of nucleoside-5’-phosphates.
- Methodologies: Typically measured spectrophotometrically by monitoring the release of inorganic phosphate from a substrate such as adenosine-5’-monophosphate (AMP).
- Clinical Significance: Elevated levels primarily indicate hepatobiliary disease (e.g., biliary obstruction, intrahepatic cholestasis). Useful in confirming that an elevated ALP is of hepatic origin, as 5’-NT is not elevated in bone diseases.
- Reference Range: Varies by laboratory but generally ranges from 2-12 U/L.
Pancreatic and Liver Enzymes
Amylase (AMY)
- Reaction Catalyzed: AMY catalyzes the hydrolysis of starch into smaller sugar molecules (maltose, glucose)
- Methodologies: Measured using enzymatic methods where amylase activity is coupled with indicator reactions, often spectrophotometrically monitoring the production of colored products or the consumption of substrates.
- Clinical Significance: Elevated levels indicate pancreatic disorders (e.g., acute pancreatitis), salivary gland inflammation, or other abdominal conditions.
- Reference Range: Varies by laboratory, generally ranging from 30-110 U/L
Lipase (LPS)
- Reaction Catalyzed: LPS catalyzes the hydrolysis of triglycerides into glycerol and fatty acids.
- Methodologies: Measured using enzymatic assays, often utilizing turbidimetric or colorimetric methods, that measure the release of fatty acids or changes in turbidity due to substrate hydrolysis.
- Clinical Significance: Elevated levels are a specific indicator of acute pancreatitis. More specific than amylase for pancreatic damage.
- Reference Range: Varies by laboratory, generally ranging from 0-160 U/L
Trypsin (TRY)
- Reaction Catalyzed: TRY catalyzes the hydrolysis of peptide bonds, specifically cleaving proteins at lysine and arginine residues.
- Methodologies: Typically measured using synthetic peptide substrates that release a chromogenic or fluorescent product upon hydrolysis by trypsin, allowing spectrophotometric or fluorometric detection. Immunological assays also exist.
- Clinical Significance: Elevated levels can be indicative of acute pancreatitis or cystic fibrosis. Immunoreactive trypsinogen (IRT) is used in newborn screening for cystic fibrosis.
- Reference Range: Varies significantly by the assay used.
Chymotrypsin (CHY)
- Reaction Catalyzed: CHY catalyzes the hydrolysis of peptide bonds, preferentially cleaving at tyrosine, phenylalanine, and tryptophan residues.
- Methodologies: Similar to trypsin assays, chymotrypsin activity is measured using synthetic peptide substrates that release a detectable product upon hydrolysis, enabling spectrophotometric or fluorometric quantification.
- Clinical Significance: Decreased levels can indicate pancreatic insufficiency or other malabsorptive disorders. Fecal chymotrypsin is sometimes measured to assess exocrine pancreatic function.
- Reference Range: Varies significantly by the assay used.
Miscellaneous Enzymes: ACP, ALD, and CHE
Acid Phosphatase (ACP)
- Reaction Catalyzed: ACP catalyzes the hydrolysis of phosphate esters at an acidic pH.
- Methodologies: Measured spectrophotometrically using substrates like p-nitrophenyl phosphate. The release of p-nitrophenol is monitored.
- Clinical Significance: Elevated in prostate cancer (especially prostatic ACP), bone diseases, and Gaucher's disease
- Reference Range: Varies, but generally up to 11 U/L.
Aldolase (ALD)
- Reaction Catalyzed: ALD catalyzes the cleavage of fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate during glycolysis and gluconeogenesis.
- Methodologies: Measured spectrophotometrically by coupling the aldolase reaction to NADH-dependent reactions.
- Clinical Significance: Elevated in muscle disorders (e.g., muscular dystrophy), liver damage, and myocardial infarction.
- Reference Range: Varies, but generally up to 8 U/L.
Cholinesterase (CHE)
- Reaction Catalyzed: CHE (also known as pseudocholinesterase or butyrylcholinesterase) catalyzes the hydrolysis of choline esters, including succinylcholine.
- Methodologies: Measured by monitoring the hydrolysis of substrates like butyrylthiocholine.
- Clinical Significance: Decreased levels can indicate liver disease, exposure to organophosphate insecticides, or genetic variants affecting enzyme activity which can prolong the effects of certain muscle relaxants used during anesthesia; increased levels may be associated with nephrotic syndrome.
- Reference Range: Varies, but generally 5,300-12,900 U/L.
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