Biochemistry Enzymes and Reactions

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Questions and Answers

What is the primary product formed when lactate is converted by lactate dehydrogenase?

Pyruvate (correct)

Hydrogen

Lactate

Ester

Which type of reaction does lactate dehydrogenase facilitate when lactate is converted to pyruvate?

Oxidation (correct)

Reduction

Hydrolysis

Decarboxylation

What is the enzyme classification for lactate dehydrogenase?

Dehydrogenase (correct)

Lyase

Transferase

Hydrolase

What does the first digit in the Enzyme Commission Nomenclature represent?

Class Signup and view all the answers

Which of the following enzymes is specifically responsible for transferring an amino group?

Aminotransferase Signup and view all the answers

What type of reaction does an isomerase catalyze?

Rearrangement of functional groups Signup and view all the answers

Which of the following enzyme classifications is responsible for the removal of carboxyl groups?

Decarboxylase Signup and view all the answers

When pyruvate is converted back into lactate, what kind of reaction occurs?

Reduction Signup and view all the answers

What is the primary target of the viral infection in Hepatitis B?

Hepatocytes facing the bloodstream Signup and view all the answers

Which liver enzyme is primarily requested for assessing hepatocellular disorders?

ALT Signup and view all the answers

Why is AST not considered a reliable marker for heart problems?

It is found in many other tissue sources. Signup and view all the answers

In the context of liver diseases, what does ULN stand for?

Upper Limit of Normal Signup and view all the answers

Which of the following is NOT a typical cause of Hepatitis B?

Airborne transmission Signup and view all the answers

What is the function of the enzyme ALT?

Transfer of an amino group Signup and view all the answers

What condition can lead to elevated levels of ALT and AST?

Liver cirrhosis Signup and view all the answers

Which enzyme is primarily found in cardiac tissues?

Troponin I Signup and view all the answers

Which organ is NOT a common source of alkaline phosphatase (ALP) isoenzyme?

Skin Signup and view all the answers

What is the primary application of ALP testing in laboratory settings?

Differentiating between bone and liver disorders Signup and view all the answers

What is the optimum pH range for alkaline phosphatase (ALP) activity?

9.0 - 10.0 Signup and view all the answers

Why is it important to differentiate ALP isoenzymes?

To determine the exact cause of high ALP levels Signup and view all the answers

Which of the following is NOT a commonly tested isoenzyme of ALP?

Pulmonary ALP Signup and view all the answers

Which cells are primarily responsible for the production of bone ALP?

Osteoblasts Signup and view all the answers

What is a key reason for testing ALP despite its high levels?

It confirms the type of disease a patient has Signup and view all the answers

How is intestinal ALP primarily bound in the body?

To bile canalicular membranes Signup and view all the answers

What is the primary function of the enzymes produced by the pancreas?

Digestion of carbohydrates and fats Signup and view all the answers

Which enzyme is NOT produced by the pancreas?

Pepsin Signup and view all the answers

What is indicated by a high level of amylase in urine?

Acute pancreatitis Signup and view all the answers

When can a rise in amylase levels be observed after the onset of acute pancreatitis?

5-8 hours after the attack Signup and view all the answers

Which isoenzyme of amylase is predominant during acute pancreatitis?

P-type isoamylase Signup and view all the answers

What is the major distinction of amylase when filtered by the glomerulus?

It is easily detected in the urine. Signup and view all the answers

At what time is amylase level expected to peak after the onset of pancreas inflammation?

24 hours after the onset Signup and view all the answers

Which location contributes to the initial digestion of starch?

Mouth Signup and view all the answers

What condition is commonly associated with cholestasis during pregnancy?

Cholestasis in pregnancy Signup and view all the answers

Which event occurs when bile flow is obstructed?

Translocation of ALP to the sinusoidal surface Signup and view all the answers

What pathological condition can result from blocked bile flow?

Cholangitis Signup and view all the answers

What leads to damage of hepatocytes in obstructive conditions?

Pressure from accumulated bile Signup and view all the answers

What role does IgG play in the bile?

Fights off infections Signup and view all the answers

In cases of bile duct blockage, which normal body process is disrupted?

Flow of intestinal flora to the bile duct Signup and view all the answers

Which liver condition is indicated by an alkaline phosphatase (ALP) level less than 3 times ULN?

Hepatitis Signup and view all the answers

What is a significant effect of cholestasis on bile flow during pregnancy?

Decreased bile flow Signup and view all the answers

Study Notes

Inflammation and Cyclooxygenase

Inflammation is initiated by cyclooxygenase, an enzyme that produces prostaglandins.
Lactate is the substrate converted to pyruvate by lactate dehydrogenase through oxidation (removal of hydrogen ion).

Enzyme Nomenclature

Enzymes are typically named by their substrate + "-ase" (not universally applicable).
Examples include:
- Lipid = lipase
- Ester = esterase
- Protein = protease
The type of reaction is indicated in enzyme names:
- Oxidation = oxidase
- Reduction = reductase
- Hydrolysis = hydrolase
- Dehydrogenase = removes hydrogen atoms
- Decarboxylase = removes carboxyl groups

Enzyme Commission Nomenclature (E.C.)

E.C. numbers classify enzymes based on:
- 1st digit: class
- 2nd digit: subclass
- 3rd & 4th: serial number
Example: E.C. 2.6.1.1 corresponds to L-Aspartate 2-Oxaloglutarate aminotransferase, which transfers amino groups.

Isomerases and Transferases

Isomerases rearrange functional groups within a molecule.
Transferases facilitate the transfer of functional groups other than hydrogen between substrates.

Amylase Properties

Molecular weight of amylase: 50,000 – 55,000.
Readily filtered by glomerulus, not reabsorbed in tubules, allowing for urine detection.
First amylase enzyme discovered was from urine sample, referred to as general amylase, not specific.

Diagnostic Significance of Amylase

Elevated amylase indicates acute pancreatitis, peaking 24 hours post-onset.
Hepatitis and cirrhosis lead to ALT and AST elevations, with chronic liver conditions presenting significantly high values (up to four times upper limit of normal).

Enzyme Classification: Alkaline Phosphatase (ALP)

Systematic name: Orthophosphoric Monoester Phosphohydrolase (Alkaline).
Optimum pH for activity: 9.0 - 10.0.
Used to confirm hepatobiliary disorders including cholestasis, biliary obstruction, and viral hepatitis.

Biliary Tract Obstruction raises ALP levels 4-10 times the upper limit of normal (ULN) due to increased synthesis induced by cholestasis.
Hepatocellular disorders typically show ALP elevations of less than three times ULN, while severe conditions may reach higher levels.
Elevated estrogen in pregnant women can lead to cholestasis, affecting bile flow and increasing the risk of cholangitis.

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Description

This quiz covers key concepts related to biochemistry, focusing on enzymes such as lactate dehydrogenase and the processes of substrate conversion. You'll explore the roles of enzymes, including cyclooxygenase and the biochemical reactions they facilitate. Test your understanding of nomenclature and oxidation reactions.