Question 1

What transferase enzyme is involved in the conversion of the stored form of energy to usable energy (adenosine triphosphate [ATP])within cardiac myocytes?

Accepted Answer

Creatine kinase is the enzyme responsible for catalyzing the transfer of a high-energy phosphate group from phosphocreatine to adenosine diphosphate (ADP), resulting in the synthesis of ATP. This process occurs rapidly and is critical for providing energy to cardiac myocytes during high-energy demand situations, such as exercise or stress. Aspartate aminotransferase and lactate dehydrogenase are enzymes involved in other metabolic pathways and are not directly involved in ATP synthesis. Troponinase is not a known enzyme and is not involved in energy metabolism.

Question 2

A hydrolase enzyme important during digestion that catalyzes the hydrolysis of starches while food is still in the mouth is:

Accepted Answer

The hydrolase enzyme important during digestion that catalyzes the hydrolysis of starches while food is still in the mouth is S-type amylase. This enzyme is also known as salivary amylase and is produced by the salivary glands. It begins the breakdown of carbohydrates into simple sugars such as glucose and maltose.

Question 3

Why is heparin the only acceptable anticoagulant to use when obtaining blood samples for ALP analysis?

Accepted Answer

Other anticoagulants can contain inhibitors of magnesium, which is essential for the activation of ALP (Alkaline Phosphatase). Magnesium acts as a cofactor for ALP, and its inhibition by other anticoagulants can lead to falsely low ALP activity readings. Heparin does not inhibit magnesium, making it the preferred anticoagulant for ALP analysis.

Question 4

Tartrate-resistant acid phosphatase (TR-ACP)that is present in unhemolyzed serum is synthesized mainly in:

Accepted Answer

Tartrate-resistant acid phosphatase (TR-ACP) is an important marker of osteoclast activity and is synthesized mainly by osteoclasts. It is involved in the bone resorption process by breaking down bone matrix. TR-ACP levels in serum are used as a diagnostic tool for assessing bone metabolism and osteoporosis.

Question 5

The principal source of serum cholinesterase (CHE)in blood is:

Accepted Answer

The principal source of serum cholinesterase (CHE) in blood is the liver, which synthesizes and secretes it into the bloodstream.

Question 6

A 37-year-old woman who thinks she might be pregnant visits her physician with a complaint of upper right quadrant pain.Blood samples are obtained.Increased enzyme activity was seen for ALP,AST,LD,and GGT.The ALP was 10 times higher than the upper reference limit.A hepatitis panel and a pregnancy test had negative results.Gel electrophoresis was done to separate ALP isoenzymes,with a dense liver band and what appeared to be a diffuse placental band.If there is not a pregnancy,what is the name given to the observed isoenzyme band that migrates in the same region as the placental isoenzyme?

Accepted Answer

The observed isoenzyme band that migrates in the same region as the placental isoenzyme is known as the Regan isoenzyme. It can also be found in patients with certain types of cancer, particularly adenocarcinomas.

Question 7

A physician orders several laboratory tests on a 55-year-old male patient who is complaining of generalized (all-over)pain,stiffness,fatigue,and headaches.Based on the following serum test results,what is the most likely diagnosis: ALP-significantly increased,GGT- normal?

Accepted Answer

Alkaline phosphatase (ALP) is a marker for bone disease, as it is found in high levels in bone tissue. The fact that the patient's ALP levels are significantly increased suggests that they may have a bone disease. The normal levels of gamma-glutamyl transpeptidase (GGT) indicate that the liver may not be the primary source of the ALP elevation, ruling out options A, B, and C.

Question 8

At present,the major diagnostic usefulness of tartrate-resistant acid phosphatase type 5b is in its use as a marker of conditions with:

Accepted Answer

Tartrate-resistant acid phosphatase type 5b is mainly used as a marker of conditions with an osteolytic component, such as osteoporosis, osteopenia, Paget's disease, and bone metastases. It can detect osteoclast activity and bone resorption, which is useful in monitoring the progression of bone diseases and assessing the effectiveness of treatments. Its diagnostic usefulness in liver involvement, pancreatitis, and prostate gland involvement is limited.

Question 9

Heart tissue contains which of the following CK isoenzymes?

Accepted Answer

Heart tissue contains both MM and MB isoenzymes of creatine kinase (CK). CK-MM is found in skeletal muscle and the heart, while CK-MB is primarily in the heart and is often measured to diagnose or monitor myocardial infarction.

Question 10

A 37-year-old woman who thinks she might be pregnant visits her physician with a complaint of upper right quadrant pain.Blood samples are obtained.Increased enzyme activity was seen for ALP,AST,lactate dehydrogenase (LD),and GGT.The ALP was 10 times higher than the upper reference limit.A hepatitis panel and a pregnancy test had negative results.Gel electrophoresis was done to separate ALP isoenzymes,with a dense liver band and what appeared to be a diffuse placental band.If this woman's physician has ruled out pregnancy,activity of what other serum enzyme could be measured to differentiate between hepatobiliary disease and liver disease?

Accepted Answer

The answer of A 37-year-old woman who thinks she might...

Question 11

Increased enzyme activity is typically observed in serum or plasma:

Accepted Answer

Increased enzyme activity is often a sign of tissue damage or injury, as enzymes are released into the bloodstream from damaged cells. This can be seen in conditions such as heart attacks or liver disease.

Question 12

A specimen is received in a green top tube (heparin)with a request for alkaline phosphatase analysis.The plasma is separated and the test is performed.How will this specimen type affect the ALP results?

Accepted Answer

This is an acceptable specimen for alkaline phosphatase analysis and will not affect the test results.

Question 13

Which of the following products are formed from the forward reaction catalyzed by ALT?

Accepted Answer

ALT (Alanine aminotransferase) catalyzes the conversion of alanine and alpha-ketoglutarate to pyruvate and glutamate.

Question 14

Which is the most sensitive enzyme for monitoring chronic alcoholic liver disease?

Accepted Answer

Gamma-glutamyl transferase (GGT) is the most sensitive marker for chronic alcoholic liver disease. It is found in cell plasma and weakly in liver cells, and its level increases with alcohol consumption. Elevated levels of GGT indicate liver damage and can help diagnose and monitor alcoholic liver disease. Other enzymes such as AST and ALP can also be elevated in liver disease, but GGT is more specific to alcohol-induced liver injury. Therefore, the correct answer is B) GGT.

Question 15

Which one of the following enzymes catalyzes the transfer of an amino group to alpha- ketoglutarate with the formation of oxaloacetate and glutamate?

Accepted Answer

Aspartate aminotransferase (AST), also known as transaminase or serum glutamic oxaloacetic transaminase (SGOT), catalyzes the transfer of an amino group from aspartate to alpha-ketoglutarate to form oxaloacetate and glutamate.

Question 16

If you were asked by your laboratory director to set up an enzyme profile (group of tests)specifically to assess hepatobiliary (biliary obstruction)disease,which one of the following sets of enzymes would be most appropriate?

Accepted Answer

The enzymes NTP (total bilirubin), ALP (alkaline phosphatase), and GGT (gamma-glutamyltransferase) are commonly used to assess hepatobiliary disease as they are elevated in cases of biliary obstruction. F1F1F1S1F1F1F10 is not a known enzyme and CK (creatine kinase) is not specific to hepatobiliary disease. Similarly, CHE (cholinesterase) and LD (lactate dehydrogenase) are not as sensitive or specific for assessing hepatobiliary disease compared to NTP, ALP, and GGT. ALT (alanine transaminase) and AST (aspartate transaminase) may also be elevated in hepatobiliary disease, but they are not as specific as ALP and GGT. Therefore, the best choice for assessing hepatobiliary disease would be NTP, ALP, and GGT.

Question 17

All of the statements below about the clinically significant phosphatases are true except they:

Accepted Answer

The clinically significant phosphatases do not catalyze the transfer of amine groups to ketoacids. Instead, they catalyze the removal of a phosphate group from a substrate molecule. They are divided into two classes based upon the pH required for their respective reactions, are isoenzyme forms of the phosphatases, and are classified as hydrolases.

Question 18

A 10-year-old girl visits her pediatrician with the complaint of bone pain.Following enzyme studies,these results were obtained: ALP 3.5 higher than upper reference limit; NTP normal.These results are consistent with a diagnosis of:

Accepted Answer

Elevated alkaline phosphatase (ALP) levels in a 10-year-old can be indicative of normal bone growth, especially if other enzymes like nucleotidase (NTP) are normal, as bone turnover can increase ALP.

Question 19

Activators that are required for normal CK activity include:

Accepted Answer

The answer of Activators that are required for normal CK...

Question 20

Which one of the following statements concerning lipase is incorrect?

Accepted Answer

Lipase is not detected in urine, as it is not excreted by the kidneys. Lipase is an enzyme that is involved in the breakdown of fats and is primarily located in the pancreas, although small amounts may be found in other tissues. Lipase activity can increase following an acute attack of pancreatitis, which is an inflammation of the pancreas. Lipase belongs to the class of hydrolase enzymes, which break down molecules by adding water.

Quiz 19: Serum Enzymes

What transferase enzyme is involved in the conversion of the stored form of energy to usable energy (adenosine triphosphate [ATP]) within cardiac myocytes?