Exam 4 Practice Questions

Lipase is predominately produced in what organ/tissue?

pancreas

What accelerates the rate of lipase activity in the body?

presence of bile salt

What is the function of LD in the body?

Interconversion of lactate and pyruvate

Which one of the following is a TRUE statement concerning alkaline phosphatase? -It is optimally active at pH 5 -It is decreased in bone disorders involving the osteoblasts -It is increased in obstructive jaundice -It is increased in myocardial infarctions

It is increased in obstructive jaundice

Isoenzymes of alkaline phosphatase occur in:

Kidney, bone, intestines, liver

When measuring enzyme activity, if the instrument is operating 5ºC lower than the temperature prescribed for the method, how will the results be affected?

Lower than actual

What coenzyme does LD use when converting lactate to pyruvate?

NAD+

Which of the following analytes would be increased due to delay in centrifugation?

AST released over time from cells into serum or plasma.

All of the following are sources of serum alkaline phosphatase EXCEPT: -liver -placenta -intestine -brain

brain

In healthy individuals, the normal ratio of AST/ALT is

<1.0.

The De Ritis ratio is the calculation of AST/ALT and is used for evaluating liver disease. What should the ratio be when ethanol-related liver disease is expected?

>2.0

Which one of the following cardiac biomarkers could detect a recent reinfarction? -Troponin T - Troponin I - LD - CK-MB

CK-MB: Following an acute myocardial infarction (AMI), elevated CK-MB returns to normal ranges in 48-96 hours. If a patient has a second AMI in this time period, a second rise in concentrations of CK-MB would be seen. This is not true for the cardiac troponins since they remain elevated for much longer periods of time following an AMI: 8-21 days for TnT and 7-14 days for TnI. LD levels are elevated for up to one week following AMI.

Which of the statements below regarding the diagnosis of pancreatitis is CORRECT? -Amylase and lipase are as predictive in chronic as in acute pancreatitis. -Diagnostic sensitivity for acute pancreatitis is increased by assaying both amylase and lipase. -Chronic pancreatitis occurs more often in women. -Increased amylase levels stay increased after the cause of the pancreatitis is removed.

Diagnostic sensitivity for acute pancreatitis is increased by assaying both amylase and lipase. Increased levels of amylase and lipase are very useful for detecting acute pancreatitis.

Elevation of serum creatine kinase may be associated with:

Duschenne muscular dystrophy or cerebrovascular accident (stroke) or vigorous exercise

The properties of enzymes are CORRECTLY described by which of the following statements? -Enzyme activity is not altered by heat denaturation -Enzymes are protein catalysts of biological origin -Enzymes are stable proteins and unaffected by pH changes -Enzymes affect the rate of a chemical reaction by raising the activation energy needed

Enzymes are protein catalysts of biological origin

What role does lipase play in the body?

Hydrolyzes fat esters to produce alcohol and fatty acids

Given the following data, what is the most likely disease state? Total bili = 4.0 (0.5-1.5) Direct bili = 3.0 (0.2-0.5) AST = 75 (2-25) ALT = 118 (2-23) LD = 220 (< 140) ALP = 841 (28-68) GGT =150 (21-40 U)

The correct answer is biliary duct obstruction, as seen by the increase in both ALP and GGT, both enzymes that are specific for biliary tree issues. The conjugated bilirubin is also increased, showing that bilirubin are getting to the liver for processing, but spilling over as it cannot be removed properly.

According to the Michaelis-Menton kinetics theory, when a reaction is performed in zero-order kinetics:

The substrate concentration is in excess and the reaction rate is dependent on the enzyme concentration

What function in the body does GGT have?

Transfer of gamma-glutamyl peptides amino acids, water, and other peptides

Mrs. Jones, a diabetic, is admitted to the hospital on November 25th. It appears that she has had an acute myocardial infarction (AMI), but did not feel the severe chest pain because of diabetic neuropathy. She has not felt well since November 20th and her physician believes she possibly had an AMI on November 20th.Assuming that the infarct was uncomplicated, which cardiac biomarker would most likely still be elevated and would assist in an AMI diagnosis?

Troponin T remains elevated after an AMI for 8-21 days, with an initial elevation within 3-12 hours after onset of myocardial necrosis. Myoglobin returns to normal range within 24-36 hours and CK-MB is back to normal range in 48-96 hours, so neither could be used in this case.

Which analyte should be increased in the presence of muscular dystrophy?

aldolase

That portion of an enzyme which when separated from its cofactor is called a(n):

apoenzyme

Which type of kinetic reactions are reactions in which the enzyme is in excess and the substrate concentration is the limiting factor?

first order

Which of the following is a liver enzyme that is instrumental in allowing glucose to enter the blood stream? -Glucose oxidase -Glucose-6-isomerase -Glucose-6-convertase -Glucose-6-phosphatase

glucose-6-phosphatase. Glucose-6-phosphatase is a liver enzyme that acts as a catalyst in the conversion of glucose-6-phosphate to glucose and inorganic phosphate. This action allows glucose in the liver to enter the peripheral blood circulation.

A patient presents with an elevation of unconjugated bilirubin, normal serum alkaline phosphatase, normal liver enzymes, and no bilirubin in the urine. This combination would suggest:

increased rate of hemolysis. Unconjugated bilirubin is a byproduct of RBC breakdown, or hemolysis. It would be expected to see an increase in unconjugated bilirubin when hemolysis is occurring at an increased rate. The liver enzymes would not remain at normal levels if there were a viral infection of the liver, chemical damage to the liver, or obstruction of bile ducts.

An important metallic activator of alkaline phosphatase and creatine kinase is:

magnesium

Which of the following conditions would be suggested by a jaundiced patient experiencing a marked rise in alkaline phosphatase (ALP), conjugated bilirubin, and a slight rise in alanine aminotransferase (ALT)?

post-hepatic cholestasis. Post-hepatic cholestasis (stoppage or suppression of the flow of bile) is characterized by jaundice, a marked increase in ALP, GGT, conjugated bilirubin, as well as other hepatic enzymes. The slight rise of ALT suggests that the issue is not hepatitis.

A reaction is in _______ kinetics when the reaction rate depends only on enzyme concentration.

zero order In this case the substrate concentration is high and the only limiting factor to the reaction and the formation of the enzyme-substrate complex is the enzyme concentration. Once all of the enzyme is bound to the substrate, no further complex concentration can occur and the maximum velocity of the reaction has been reached.

Which two of the following biomarkers are not specific to cardiac muscle and may be elevated in patients with injury to muscle other than cardiac muscle? - cTnI and cTnT - CK-MB and myoglobin - cTnT and CK-MB - Myoglobin and cTnI

-CK-MB and myoglobin Troponin T and I tests are much more specific to cardiac muscle than myoglobin and CK-MB assays.

The recommended storage temperature for the preservation of activity for MOST enzymes is:

4C