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How are enzyme reactions performed (with substrate in excess)?
Zero-order kinetics
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What are the 2 test methods used to measure enzyme reactions?
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What test methodology is a type of reaction that combines reactants, stops the reaction at a fixed time, then measures the product formed?
Endpoint
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What test methodology is a type of reaction that combines reactants, then measures the change in absorbance at specific interfals over a specific time period?
Kinetic
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How are enzymes reported and why are they reported that way?
Reported in activity units (because they are measured based on their activity instead of their concentration)
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What is the quantity of enzyme that catalyzes the reaction of one micromole of substrate per minute under specified conditions?
International units (IU or U)
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Where are the highest concentrations of lactate dehydrongenase (LD) located?
- Liver
- Heart
- Skeletal muscle
- Kidney
- Erythrocytes
- Lesser amounts in other tissues
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What do LD isoenzymes consist of?
Four subunits (polypeptide chains) - derived from 2 types of polypeptides designated M (muscle/liver) and H (heart)
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What clinical conditions is associated with elevated LD values?
- Cardiac disorders (acute myocardial infarction)
- Hepatic disease (viral hepatitis, cirrhosis, infectious mononucleosis)
- Skeletal muscle diseases
- Hemolytic and hematologic disorders (pernicious anemia exhibits extreme elvations of LD)
- Neoplastic disorders (acute lymphoblastic leukemia)
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In AMI, how do the levels of LD rise and fall?
- Rise within 8-12 hours
- Peak at 24-48 hours
- Return to normal in 7-10 days
- Not used to diagnose AMI
- Useful when assessing concurrent liver damage
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What is the reference rang of LD?
100-225 U/L at 37 degrees celcius
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Where are the highest concentrations of Creatine kinase (CK) and CK Isoenzymes located?
- Skeletal muscle
- Heart muscle
- Brain tissue
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What do the CK isoenzymes consist of?
2 subunits: M (muscle) and B (brain)
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What is the clinical significance of an increase in CK-MB?
- Heart muscle damage
- Indicative of AMI (when used in conjunction with other markers)
- Skeletal muscle damage
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What is the clinical significance of an increase of CK-MM?
- Skeletal muscle disorder
- Heart muscle disorder
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What is the clinical significance of and increase in CK-BB?
- CNS disorders
- Tumors of various organs, including the prostate gland
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What is the clinical significance of an increase of CK?
- Cardiac disorders (AMI)
- Skeletal muscle disorders (muscular dystrophy)
- CNS disorders (seizures and cerebral vascular accidents)
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When do the CK-MB values rise and fall following AMI?
- Rise within 4-6 hours
- Peak 12-24 hours
- Return to normal at 2-3 days
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What is the reference range of CK?
- Male: 15-160 U/L
- Female: 15-130 U/L
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What is the reference range of CK-MB?
- <6% of CK value
- Mass assay: 0-5 ng/mL
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Where are the highest concentrations of Aspartate aminotransferase (AST) located?
- Heart
- Liver
- Skeletal muscle
- Lesser ammounts in kidney and other tissues (including erythrocytes)
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What clinical conditions are associated with AST?
- Hepatocellular disorders
- Skeletal muscle disorders
- Pulmonary emboli
- Acute pancreatitis
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What is the reference range for AST?
5-30 U/L
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Where are the highest concentrations of alanine aminotransferase (ALT) located?
- Liver
- Lesser amounts in other tissues (kidneys and erythrocytes)
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What clinical conditions are associated with ALT?
Hepatocellular disorders
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What is more specific indicator of liver disease, AST or ALT?
ALT
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What is the reference range for ALT?
6-37 U/L
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Where are the highest concentrations of alkaline phophatase (ALP) located?
- Liver
- Bone
- Intestines
- Spleen
- Kidney
- Placenta
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What is the clinical significance of increased ALP?
- Hepatobiliary disease
- Bone disorders
- Paget disease
- Healing bone fractures
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In hepatobiliary disorders that are caused by obstructive diseases, what lab would be more increased, AST, ALT, or ALP?
ALP
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What causes a decrease of ALP levels?
Hypophophatasia (lack of ALP bone isoenzyme) - characterized by insufficient bone calcification
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What is the reference range of ALP?
- Adults: 50-115 U/L
- Children (4-15 yrs): 54-369 U/L
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Where are the highest concentrations of Acid phosphatase (ACP) located?
- Prostate gland
- Lesser amounts in bone, liver, spleen, erythrocytes, plts
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What causes an increase of acid phosphatase (ACP)?
- Prostate cancer
- Benign prostatic hypertrophy
- Bone disease
- Paget disease
- Breast cancer with bone metastases
- Gaucher disease
- Plt damage
- Idiopathic thrombocytopenic purpura
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What are the reference ranges of acid phosphatase (ACP)?
- Total ACP Male: 2.5-11.7 U/L
- Total ACP Female: 0.3-9.2 U/L
- Prostatic ACP Male: 0.2-5.0 U/L
- Prostatic ACP Female: 0.0-0.8 U/L
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Where are the highest concentrations of gamma-glutamyltransferase (GGT) located?
- Liver
- Kidneys
- Pancreas
- Intestine
- NOT found in Skeletal muscle or bone
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What causes an increase of GGT?
- Hepatobiliary diseases
- Intra- and posthepatic biliary tract obstruction
- Induced by drugs and alcohol
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What is the reference range of GGT?
- Male: up to 55 U/L
- Female: up to 38 U/L
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Where is amylase found?
- Pancreas
- Salivary glands
- Small intestine
- Fallopian tubes
- Other tissues
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What causes an increase of amylase?
- Acute pancreatitis
- Mumps
- Perforated peptic ulcer
- Intestinal obstruction
- Cholecystitis
- Ruptured ectopic pregnancy
- mesenteric infarction
- Acute appendicitis
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Where is lipase found?
- Pancreas
- Lesser amounts in gastric mucosa, intestinal mucosa, adipose tissue
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What causes an increase of lipase?
- Acute pancreatitis
- Perforated peptic ulcer
- Duodenal ulcer
- Intestinal obstruction
- Cholecystitis
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What is the reference range for lipase?
Up to 38 U/L
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Where is True cholinesterase found?
- RBCs
- Lungs
- Spleen
- Nerve endings
- Gray matter of the brain
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Where is pseudocholinesterase found?
- Liver
- Pancreas
- Heart
- White matter of brain
- Serum
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What causes a decrease in pseudocholinesterase?
- Hepatocellular disease (due to decreased synthesis)
- Insecticide poisonings
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What is the reference range for psuedocholinesterase?
- Male: 40-78 U/L
- Female: 33-76 U/L
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Where s glucose-6-phosphate dehydrogenase (G6PD) found?
- Erythrocytes
- Adrenal glands
- Thymus
- Lymph nodes
- Spleen
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What causes a decrease in G6PD?
- Inherited as a sex-linked trait
- Drug induced hemolytic anemia
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What causes an increase of G6PD?
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G6PD requires the analysis of a ___ ____ ____ ______
Red blood cell hemolysate
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What is the reference range for G6PD?
8-14 U/g Hgb
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