Lactate is produced as a byproduct of which metabolic process?
Amino acid synthesis
Aerobic glucose metabolism
Anaerobic glucose metabolism (when oxygen is severely diminished)
Fatty acid breakdown
Lactate is produced as a byproduct of which metabolic process?
Amino acid synthesis
Aerobic glucose metabolism
Anaerobic glucose metabolism (when oxygen is severely diminished)
Fatty acid breakdown
What is the normal end product of glycolysis under adequate oxygen conditions?
Lactate
Pyruvate
ATP
Acetyl-CoA
What is the normal end product of glycolysis under adequate oxygen conditions?
Lactate
Pyruvate
ATP
Acetyl-CoA
Conversion of pyruvate to lactate is triggered by:
Increased acetyl-CoA formation
High levels of NAD⁺ relative to NADH
High glucose intake
Oxygen deficiency leading to excess NADH accumulation
Conversion of pyruvate to lactate is triggered by:
Increased acetyl-CoA formation
High levels of NAD⁺ relative to NADH
High glucose intake
Oxygen deficiency leading to excess NADH accumulation
How much ATP is generated per mole of glucose metabolized to lactate under hypoxic conditions?
10 mol
18 mol
2 mol
38 mol
How much ATP is generated per mole of glucose metabolized to lactate under hypoxic conditions?
10 mol
18 mol
2 mol
38 mol
Excess blood lactate is clinically important because it indicates:
Normal metabolic function
Adequate tissue oxygenation
High glucose levels
Severity of oxygen deprivation
Excess blood lactate is clinically important because it indicates:
Normal metabolic function
Adequate tissue oxygenation
High glucose levels
Severity of oxygen deprivation
Unlike ions such as K⁺ or Ca²⁺, lactate is not specifically regulated because:
It is only produced in muscles
It is stored in bones
The kidneys rapidly excrete it
It is a byproduct of anaerobic metabolism, not a regulated electrolyte
Unlike ions such as K⁺ or Ca²⁺, lactate is not specifically regulated because:
It is only produced in muscles
It is stored in bones
The kidneys rapidly excrete it
It is a byproduct of anaerobic metabolism, not a regulated electrolyte
Blood lactate levels rise and indicate tissue hypoxia:
At the same time as pH changes
Later than pH changes
Earlier than pH changes
Only after pH becomes severely acidic
Blood lactate levels rise and indicate tissue hypoxia:
At the same time as pH changes
Later than pH changes
Earlier than pH changes
Only after pH becomes severely acidic
The major organ responsible for removing lactate from the bloodstream is the:
Lungs
Kidneys
Liver
Heart
The major organ responsible for removing lactate from the bloodstream is the:
Lungs
Kidneys
Liver
Heart
The liver removes lactate by converting it back to glucose through:
Lipolysis
Glycolysis
The citric acid cycle
Gluconeogenesis
The liver removes lactate by converting it back to glucose through:
Lipolysis
Glycolysis
The citric acid cycle
Gluconeogenesis
Blood lactate measurements are NOT used for which of the following?
Indicating illness severity
Diagnosing vitamin B12 deficiency
Determining patient prognosis
Metabolic monitoring of critically ill patients
Blood lactate measurements are NOT used for which of the following?
Indicating illness severity
Diagnosing vitamin B12 deficiency
Determining patient prognosis
Metabolic monitoring of critically ill patients
Type A lactic acidosis is associated with:
Hypoxic conditions
Metabolic disorders unrelated to oxygen
Toxin exposure
Liver disease
Type A lactic acidosis is associated with:
Hypoxic conditions
Metabolic disorders unrelated to oxygen
Toxin exposure
Liver disease
Which of the following is an example of a condition causing Type A lactic acidosis?
Salicylate poisoning
Diabetes mellitus
Shock
Severe infection
Which of the following is an example of a condition causing Type A lactic acidosis?
Salicylate poisoning
Diabetes mellitus
Shock
Severe infection
Type B lactic acidosis has which origin?
Cardiac
Metabolic
Respiratory
Hypoxic
Type B lactic acidosis has which origin?
Cardiac
Metabolic
Respiratory
Hypoxic
All of the following are causes of Type B lactic acidosis EXCEPT:
Renal disease
Leukemia
Ethanol poisoning
Myocardial infarction
All of the following are causes of Type B lactic acidosis EXCEPT:
Renal disease
Leukemia
Ethanol poisoning
Myocardial infarction
Special specimen handling is required for lactate analysis primarily because:
Tourniquets have no impact on results
It is only stable in urine samples
Hemolysis decreases lactate levels
Lactate levels can change rapidly after collection due to ongoing metabolism
Special specimen handling is required for lactate analysis primarily because:
Tourniquets have no impact on results
It is only stable in urine samples
Hemolysis decreases lactate levels
Lactate levels can change rapidly after collection due to ongoing metabolism
Based on Figure 11.8, how many moles of ATP are generated via aerobic metabolism of 1 mole of glucose?
38 mol
2 mol
16 mol
24 mol
Based on Figure 11.8, how many moles of ATP are generated via aerobic metabolism of 1 mole of glucose?
38 mol
2 mol
16 mol
24 mol
In anaerobic metabolism, pyruvate is converted to lactate because:
Acetyl-CoA production is enhanced
Oxygen is abundant and drives the reaction
Glucose breakdown stops at pyruvate
Oxidative phosphorylation is absent, causing NADH to accumulate
In anaerobic metabolism, pyruvate is converted to lactate because:
Acetyl-CoA production is enhanced
Oxygen is abundant and drives the reaction
Glucose breakdown stops at pyruvate
Oxidative phosphorylation is absent, causing NADH to accumulate
A tourniquet should generally be avoided for lactate sampling because:
It dilutes the blood sample
It causes hemolysis of red blood cells
Venous stasis increases lactate levels due to local tissue hypoxia
It inhibits lactate oxidase activity
A tourniquet should generally be avoided for lactate sampling because:
It dilutes the blood sample
It causes hemolysis of red blood cells
Venous stasis increases lactate levels due to local tissue hypoxia
It inhibits lactate oxidase activity
What should a patient avoid doing before blood collection?
Sitting for 10 minutes before collection
Exercising or clenching the hand before/during collection
Eating for 2 hours before collection
Drinking water before collection
What should a patient avoid doing before blood collection?
Sitting for 10 minutes before collection
Exercising or clenching the hand before/during collection
Eating for 2 hours before collection
Drinking water before collection
What is the purpose of additives like iodoacetate and fluoride in lactate samples?
Preserve red blood cells
Increase lactate stability at room temperature
Inhibit glycolysis and prevent glucose-to-lactate conversion
Enhance clotting
What is the purpose of additives like iodoacetate and fluoride in lactate samples?
Preserve red blood cells
Increase lactate stability at room temperature
Inhibit glycolysis and prevent glucose-to-lactate conversion
Enhance clotting
Heparinized blood for lactate analysis must be delivered in what manner?
Stored at 37°C for 24 hours
Mixed with saline before processing
Left uncentrifuged until testing
Delivered on ice and plasma separated quickly to prevent metabolic changes
Heparinized blood for lactate analysis must be delivered in what manner?
Stored at 37°C for 24 hours
Mixed with saline before processing
Left uncentrifuged until testing
Delivered on ice and plasma separated quickly to prevent metabolic changes
Which of the following does NOT occur due to hypoxia leading to cell death?
NADH accumulates while NAD⁺ levels decline
Pyruvate converts to acetyl-CoA instead of lactate
Intracellular ionic balance is disrupted (increased Ca²⁺/Na⁺; decreased K⁺/Mg²⁺)
Decreased tissue oxygen supply slows oxidative metabolism
Which of the following does NOT occur due to hypoxia leading to cell death?
NADH accumulates while NAD⁺ levels decline
Pyruvate converts to acetyl-CoA instead of lactate
Intracellular ionic balance is disrupted (increased Ca²⁺/Na⁺; decreased K⁺/Mg²⁺)
Decreased tissue oxygen supply slows oxidative metabolism
Older methods for measuring lactate were considered limited because they were:
Too sensitive to small changes in lactate levels
Unable to distinguish between lactate and pyruvate
Only compatible with urine samples
Slow and laborious
Older methods for measuring lactate were considered limited because they were:
Too sensitive to small changes in lactate levels
Unable to distinguish between lactate and pyruvate
Only compatible with urine samples
Slow and laborious
Current methods for lactate determination are primarily:
Enzymatic and readily available for clinical use
Based on measuring blood flow with indwelling catheters
Pulse oximetry-based
Colorimetric without enzyme use
Current methods for lactate determination are primarily:
Enzymatic and readily available for clinical use
Based on measuring blood flow with indwelling catheters
Pulse oximetry-based
Colorimetric without enzyme use
Which enzyme is most commonly used for lactate measurement?
Pyruvate kinase
Peroxidase
Lactate oxidase
Lactate dehydrogenase
Which enzyme is most commonly used for lactate measurement?
Pyruvate kinase
Peroxidase
Lactate oxidase
Lactate dehydrogenase
What reaction does lactate oxidase catalyze?
Pyruvate + O₂ → lactate + H₂O₂
Lactate + O₂ → pyruvate + H₂O₂
Lactate + H₂O₂ → pyruvate + O₂
Pyruvate + H₂O₂ → lactate + O₂
What reaction does lactate oxidase catalyze?
Pyruvate + O₂ → lactate + H₂O₂
Lactate + O₂ → pyruvate + H₂O₂
Lactate + H₂O₂ → pyruvate + O₂
Pyruvate + H₂O₂ → lactate + O₂
In the coupled reaction for lactate measurement, peroxidase produces a colored dye from:
NADH, NAD⁺, and chromogen
Lactate, oxygen, and chromogen
Hydrogen peroxide, an H donor, and chromogen
Pyruvate, hydrogen peroxide, and an H donor
In the coupled reaction for lactate measurement, peroxidase produces a colored dye from:
NADH, NAD⁺, and chromogen
Lactate, oxygen, and chromogen
Hydrogen peroxide, an H donor, and chromogen
Pyruvate, hydrogen peroxide, and an H donor
Which of the following is NOT an alternative method to assess tissue oxygenation besides blood lactate measurements?
Base-excess determinations
Indwelling catheters to measure blood flow
Pulse oximetry
Cholesterol testing
Which of the following is NOT an alternative method to assess tissue oxygenation besides blood lactate measurements?
Base-excess determinations
Indwelling catheters to measure blood flow
Pulse oximetry
Cholesterol testing
As hypoxia disrupts intracellular ionic balance, it causes:
Increased Ca²⁺ and Na⁺; decreased K⁺ and Mg²⁺
Decreased Ca²⁺ and Na⁺; increased K⁺ and Mg²⁺
No changes in cation levels
Decreased levels of all cations
As hypoxia disrupts intracellular ionic balance, it causes:
Increased Ca²⁺ and Na⁺; decreased K⁺ and Mg²⁺
Decreased Ca²⁺ and Na⁺; increased K⁺ and Mg²⁺
No changes in cation levels
Decreased levels of all cations
In aerobic metabolism, NADH is oxidized back to NAD⁺ via:
Gluconeogenesis in the liver
Anaerobic glycolysis
Conversion of pyruvate to lactate
Oxidative phosphorylation in mitochondria
In aerobic metabolism, NADH is oxidized back to NAD⁺ via:
Gluconeogenesis in the liver
Anaerobic glycolysis
Conversion of pyruvate to lactate
Oxidative phosphorylation in mitochondria
Lactate is produced as a byproduct of which metabolic process?
Aerobic glucose metabolism
Anaerobic glucose metabolism (when oxygen is severely diminished)
Amino acid synthesis
Fatty acid breakdown
What is the normal end product of glycolysis under adequate oxygen conditions?
Lactate
Acetyl-CoA
ATP
Pyruvate
Conversion of pyruvate to lactate is triggered by:
Increased acetyl-CoA formation
Oxygen deficiency leading to excess NADH accumulation
High glucose intake
High levels of NAD⁺ relative to NADH
How much ATP is generated per mole of glucose metabolized to lactate under hypoxic conditions?
38 mol
2 mol
10 mol
18 mol
Excess blood lactate is clinically important because it indicates:
High glucose levels
Adequate tissue oxygenation
Severity of oxygen deprivation
Normal metabolic function
Unlike ions such as K⁺ or Ca²⁺, lactate is not specifically regulated because:
It is a byproduct of anaerobic metabolism, not a regulated electrolyte
The kidneys rapidly excrete it
It is only produced in muscles
It is stored in bones
Blood lactate levels rise and indicate tissue hypoxia:
Only after pH becomes severely acidic
Earlier than pH changes
Later than pH changes
At the same time as pH changes
The major organ responsible for removing lactate from the bloodstream is the:
Kidneys
Heart
Lungs
Liver
The liver removes lactate by converting it back to glucose through:
Gluconeogenesis
The citric acid cycle
Glycolysis
Lipolysis
Blood lactate measurements are NOT used for which of the following?
Diagnosing vitamin B12 deficiency
Determining patient prognosis
Metabolic monitoring of critically ill patients
Indicating illness severity
Type A lactic acidosis is associated with:
Toxin exposure
Metabolic disorders unrelated to oxygen
Liver disease
Hypoxic conditions
Which of the following is an example of a condition causing Type A lactic acidosis?
Shock
Diabetes mellitus
Salicylate poisoning
Severe infection
All of the following are causes of Type B lactic acidosis EXCEPT:
Myocardial infarction
Ethanol poisoning
Renal disease
Leukemia
Special specimen handling is required for lactate analysis primarily because:
Tourniquets have no impact on results
Hemolysis decreases lactate levels
It is only stable in urine samples
Lactate levels can change rapidly after collection due to ongoing metabolism
Based on Figure 11.8, how many moles of ATP are generated via aerobic metabolism of 1 mole of glucose?
16 mol
2 mol
24 mol
38 mol
In anaerobic metabolism, pyruvate is converted to lactate because:
Oxidative phosphorylation is absent, causing NADH to accumulate
Oxygen is abundant and drives the reaction
Glucose breakdown stops at pyruvate
Acetyl-CoA production is enhanced
A tourniquet should generally be avoided for lactate sampling because:
It dilutes the blood sample
It causes hemolysis of red blood cells
It inhibits lactate oxidase activity
Venous stasis increases lactate levels due to local tissue hypoxia
What should a patient avoid doing before blood collection?
Sitting for 10 minutes before collection
Exercising or clenching the hand before/during collection
Drinking water before collection
Eating for 2 hours before collection
What is the purpose of additives like iodoacetate and fluoride in lactate samples?
Inhibit glycolysis and prevent glucose-to-lactate conversion
Increase lactate stability at room temperature
Enhance clotting
Preserve red blood cells
Heparinized blood for lactate analysis must be delivered in what manner?
Left uncentrifuged until testing
Stored at 37°C for 24 hours
Mixed with saline before processing
Delivered on ice and plasma separated quickly to prevent metabolic changes
Which of the following does NOT occur due to hypoxia leading to cell death?
Intracellular ionic balance is disrupted (increased Ca²⁺/Na⁺; decreased K⁺/Mg²⁺)
Decreased tissue oxygen supply slows oxidative metabolism
Pyruvate converts to acetyl-CoA instead of lactate
NADH accumulates while NAD⁺ levels decline
Older methods for measuring lactate were considered limited because they were:
Too sensitive to small changes in lactate levels
Slow and laborious
Unable to distinguish between lactate and pyruvate
Only compatible with urine samples
Current methods for lactate determination are primarily:
Colorimetric without enzyme use
Based on measuring blood flow with indwelling catheters
Enzymatic and readily available for clinical use
Pulse oximetry-based
Which enzyme is most commonly used for lactate measurement?
Peroxidase
Lactate dehydrogenase
Pyruvate kinase
Lactate oxidase
What reaction does lactate oxidase catalyze?
Lactate + O₂ → pyruvate + H₂O₂
Pyruvate + H₂O₂ → lactate + O₂
Lactate + H₂O₂ → pyruvate + O₂
Pyruvate + O₂ → lactate + H₂O₂
In the coupled reaction for lactate measurement, peroxidase produces a colored dye from:
Hydrogen peroxide, an H donor, and chromogen
Pyruvate, hydrogen peroxide, and an H donor
Lactate, oxygen, and chromogen
NADH, NAD⁺, and chromogen
Which of the following is NOT an alternative method to assess tissue oxygenation besides blood lactate measurements?
Base-excess determinations
Indwelling catheters to measure blood flow
Cholesterol testing
Pulse oximetry
As hypoxia disrupts intracellular ionic balance, it causes:
Decreased levels of all cations
No changes in cation levels
Decreased Ca²⁺ and Na⁺; increased K⁺ and Mg²⁺
Increased Ca²⁺ and Na⁺; decreased K⁺ and Mg²⁺
In aerobic metabolism, NADH is oxidized back to NAD⁺ via:
Gluconeogenesis in the liver
Anaerobic glycolysis
Conversion of pyruvate to lactate
Oxidative phosphorylation in mitochondria
Lactate is produced primarily through anaerobic metabolism when oxygen levels are low.
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