أسئلة المحاضرة الـ 11 بيو (قبل التعديل)
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Questions and Answers

What distinguishes true isoenzymes from multiple forms of an enzyme?

  • They have different catalytic activities.
  • They differ in electrophoretic mobility.
  • They are produced by more than one gene. (correct)
  • They undergo post-translational modifications.

Which statement about lactate dehydrogenase (LDH) is correct?

  • LDH can only be found in the heart.
  • LDH consists of four subunits, each called a protomer. (correct)
  • LDH does not have variations in its electromagnetic mobility.
  • LDH is formed of two protein subunits.

What is the role of post-translational modifications in enzyme variation?

  • They increase the number of genes involved in enzyme production.
  • They enhance the enzyme's stability against inhibitors.
  • They produce variations in the subunits from the same gene. (correct)
  • They lead to changes in the catalytic regions of enzymes.

Which of the following is an example of multiple forms of an enzyme?

<p>Creatine kinase (CK) (C), Lactate dehydrogenase (LDH) (D)</p> Signup and view all the answers

Which subunit types are associated with creatine kinase (CK)?

<p>H (heart) and M (muscle) (B)</p> Signup and view all the answers

Which type of plasma enzymes are present in higher concentrations compared to tissues?

<p>Non-functional plasma enzymes (A)</p> Signup and view all the answers

What is the primary function of functional plasma enzymes?

<p>They have known physiological functions. (C)</p> Signup and view all the answers

Which enzyme is typically associated with assessing blood diseases?

<p>Lactate dehydrogenase (D)</p> Signup and view all the answers

What effect does liver disease have on the concentration of certain enzymes?

<p>It decreases the concentration of specific enzymes. (A)</p> Signup and view all the answers

What is a consequence of increased permeability of the cell membrane?

<p>Cell damage and enzyme release into the blood (A)</p> Signup and view all the answers

Which of the following is NOT a typical site for the synthesis of non-functional plasma enzymes?

<p>Lungs (D)</p> Signup and view all the answers

Which isoenzyme is primarily associated with myocardial infarction?

<p>Creatine kinase (CK) (C), Lactate dehydrogenase (LDH) (D)</p> Signup and view all the answers

Which enzyme is associated primarily with liver diseases?

<p>Alkaline phosphatase (D)</p> Signup and view all the answers

Which of the following conditions does creatine kinase (CK) increase in?

<p>Myocardial infarction (D)</p> Signup and view all the answers

Which factor can lead to enzyme release into the bloodstream?

<p>Tissue hypoxia due to obstruction (B)</p> Signup and view all the answers

Which isoenzyme increases specifically with leukemia?

<p>Lactate dehydrogenase (LDH) (C)</p> Signup and view all the answers

What is one of the clinical significances of isoenzymes?

<p>They help in differentiating diseases affecting organs (A)</p> Signup and view all the answers

What disease is associated with an increase in lactate dehydrogenase enzyme?

<p>Viral hepatitis (D)</p> Signup and view all the answers

What organ condition can be indicated by the rise of creatine kinase (CK)?

<p>Brain tumors (C)</p> Signup and view all the answers

Which of the following conditions is NOT indicated by an increase in lactate dehydrogenase?

<p>Skeletal muscle diseases (A)</p> Signup and view all the answers

Which isoenzyme would NOT be relevant for differentiating between brain diseases and skeletal muscle diseases?

<p>Amylase (D)</p> Signup and view all the answers

What is a characteristic of true isoenzymes?

<p>They are produced by more than one gene. (D)</p> Signup and view all the answers

Which of the following statements accurately describes lactate dehydrogenase (LDH)?

<p>LDH can exist in multiple forms depending on tissue type. (A)</p> Signup and view all the answers

What defines the electrophoretic mobility of an enzyme?

<p>The enzyme's migration in an electric field. (C)</p> Signup and view all the answers

Which of the following enzymes is characterized as a dimer?

<p>Creatine kinase (CK) (A)</p> Signup and view all the answers

What is the primary form of creatine kinase (CK) found in the heart?

<p>H (heart) (A)</p> Signup and view all the answers

What is one of the primary medical significances of lactate dehydrogenase in relation to diseases?

<p>It has a diagnostic relevance to heart diseases. (D)</p> Signup and view all the answers

Which of the following conditions is associated with an increase in the enzyme serum glutamic pyruvic transaminase?

<p>Liver diseases. (C)</p> Signup and view all the answers

How does liver disease affect the concentration of functional plasma enzymes?

<p>Decreases their concentration. (C)</p> Signup and view all the answers

Which enzyme is likely elevated in both liver and heart diseases?

<p>Lactate dehydrogenase. (A)</p> Signup and view all the answers

Which enzyme is specifically related to detecting brain diseases?

<p>Creatine kinase. (B)</p> Signup and view all the answers

What is a common outcome of cell damage regarding enzyme presence in the blood?

<p>Certain enzymes leak into the bloodstream. (D)</p> Signup and view all the answers

Which of the following diseases is most likely indicated by elevated alkaline phosphatase?

<p>Liver disease. (C)</p> Signup and view all the answers

In which scenario would a non-functional plasma enzyme likely be present in higher concentration?

<p>In specific disease states. (D)</p> Signup and view all the answers

Which disease is NOT indicated by an increase in lactate dehydrogenase (LDH)?

<p>Brain tumors (D)</p> Signup and view all the answers

Creatine kinase (CK) is primarily associated with increases in which of the following conditions?

<p>Skeletal muscle diseases (B)</p> Signup and view all the answers

Which isoenzyme is primarily used to diagnose heart diseases?

<p>Lactate dehydrogenase (LDH) (C)</p> Signup and view all the answers

What is the significance of measuring isoenzymes in clinical settings?

<p>Differentiating between organ-specific diseases (A)</p> Signup and view all the answers

Increases in creatine kinase (CK) levels can indicate which of the following diseases?

<p>Skeletal muscle dystrophy (D)</p> Signup and view all the answers

Which factor is NOT typically associated with an increase in creatine kinase (CK) levels?

<p>Viral hepatitis (D)</p> Signup and view all the answers

Which condition indicates a significant increase in lactate dehydrogenase (LDH) levels?

<p>Myocardial infarction (C)</p> Signup and view all the answers

Flashcards

Isoenzymes

Enzymes with the same catalytic activity but different physical properties, like electrophoretic mobility and susceptibility to inhibitors.

True genetic variants (True isoenzymes)

Isoenzymes created by different genes. Each gene produces one subunit of the protein.

Multiple forms - post-translational modifications

Isoenzymes created by the same gene, but the subunits undergo different post-translational modifications in different tissues.

Lactate dehydrogenase (LDH)

A tetrameric enzyme, containing four protein subunits (H or M), involved in lactate metabolism.

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Creatine kinase (CK)

A dimeric enzyme, containing two protein subunits (M or B), involved in muscle energy metabolism.

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Diagnostic Value of Isoenzymes

Measurement of specific isoenzymes in blood can help pinpoint the site of tissue damage.

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LDH1 Elevated

Elevated levels of LDH isoenzyme 1 indicate a heart attack.

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LDH5 Elevated

High levels of LDH5 suggest a liver disease like viral hepatitis.

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CK-MB Elevated

Increased levels of CK-MB often signify a myocardial infarction.

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CK-BB Elevated

Elevated CK-BB isoenzyme indicates brain tumors.

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CK-MM Elevated

Higher levels of CK-MM usually point to skeletal muscle injuries.

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Applications of Isoenzymes in Medicine

Isoenzymes can differentiate between various diseases affecting the heart, liver, and brain.

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Non-functional Plasma Enzymes

Enzymes found in blood that have no known function in the bloodstream. Their presence in blood usually indicates tissue damage.

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Functional Plasma Enzymes

Enzymes found in blood that have a specific function in the bloodstream. Their levels can be used as indicators of disease or organ damage.

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Serum Glutamic Pyruvic Transaminase (SGPT)

An enzyme found in the liver, its levels can be elevated due to liver damage and various diseases.

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Plasma Concentration of Functional Enzymes

Enzymes that are present in the bloodstream at high concentrations compared to tissues.

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Plasma Concentration of Non-functional Enzymes

Enzymes that are present in the bloodstream at very low concentrations compared to tissues.

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Cell Damage and Enzyme Release

The release of enzymes from damaged cells into the bloodstream, leading to elevated levels of these enzymes.

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What are isoenzymes?

Isoenzymes are different molecular forms of an enzyme that have the same catalytic activity but differ in physical properties, such as electrophoretic mobility and susceptibility to inhibitors.

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How are true isoenzymes formed?

True genetic variants, also known as true isoenzymes, are produced by multiple genes. Each gene codes for a specific subunit of the enzyme.

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What about isoenzymes from post-translational modifications?

These isoenzymes are created from the same gene but undergo different post-translational modifications in different tissues. These modifications alter the enzyme's structure and function.

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Explain the different subunits of Lactate dehydrogenase (LDH)

Lactate dehydrogenase (LDH) is a tetramer, consisting of four subunits, either H (heart) or M (muscle). The specific combination of subunits affects the enzyme's activity. For example, LDH1 (H4) is associated with heart tissue, while LDH5 (M4) is found in skeletal muscle.

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What are the subunits of Creatine kinase (CK) and their significance?

Creatine kinase (CK) is a dimer, composed of two subunits, M (muscle) or B (brain). CK-MB, with one M and one B subunit, is specifically elevated during heart attacks.

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True Isoenzymes

Enzymes that catalyze the same reaction but have different structures and properties. They are coded by different genes.

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Multiple Forms of Enzymes

Enzymes that catalyze the same reaction but differ due to post-translational modifications, like phosphorylation or glycosylation.

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LDH1: The 'Heart Isoenzyme'

LDH1 is the most prevalent isoenzyme in the heart. Elevated LDH1 levels indicate heart damage or a heart attack.

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LDH5: The 'Liver Isoenzyme'

LDH5 is abundant in the liver. Elevated LDH5 levels suggest liver problems like viral hepatitis.

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CK-MB: The 'Heart Attack Isoenzyme'

CK-MB is a specific isoenzyme found primarily in the heart. Elevated CK-MB levels indicate myocardial infarction or heart attack.

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Heart Attack

A heart attack is a medical emergency. Seek immediate medical attention for chest pain, shortness of breath, or discomfort.

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Study Notes

Biochemistry Lecture Notes

  • Isoenzymes: Different molecular forms of an enzyme with the same catalytic activity but physically distinct. They differ in electrophoretic mobility (movement in an electric field) and susceptibility to inhibitors.
  • Isoenzyme Sources: True isoenzymes result from true genetic variants, where different genes produce separate subunits. Multiple forms can arise from post-translational modifications of subunits from the same gene, leading to variations in different organs.
  • Isoenzyme Examples: Lactate dehydrogenase (LDH), creatine kinase (CK), acid phosphatase, and alkaline phosphatase are examples of isoenzymes.
  • LDH (Lactate Dehydrogenase): A tetramer of four protein subunits (protomer). It comes in five forms (LDH1-LDH5) designated by different combinations of H (heart) and M (muscle) subunits.
    • LDH Function: Clinically important for differentiating heart, liver, and blood diseases. Increased levels often indicate problems like myocardial infarction or viral hepatitis.
  • CK (Creatine Kinase): A dimer formed by two protein subunits. Isoenzymes include CK-BB (brain), CK-MB (cardiac/skeletal), and CK-MM (muscle).
    • CK Function: Important for diagnosis, particularly in distinguishing brain, heart, and skeletal muscle diseases. Increased CK-MB activity can signify myocardial infarction.
  • Plasma Enzymes:
    • Functional Plasma Enzymes: Present in plasma at higher concentrations compared to tissues. They have known functions (e.g., clotting factors, lipoprotein lipase).
    • Non-functional Plasma Enzymes: Exist in plasma at lower levels. They lack known functions in plasma.
    • Clinical Significance: Decreased levels of certain enzymes in liver diseases correlate to liver damage or disease. Increased plasma levels often indicate problems like liver or heart disease, bone disease, and obstructive or other diseases. Different enzymes are elevated in varying diseases.
    • Enzyme Classification (Non-functional): Functional plasma enzymes have known functions, measured in higher concentrations in plasma than in tissue. Non-functional enzymes have unknown functions; measured at low concentrations.

Medical Importance of Isoenzymes

  • Isoenzymes Diagnostic Value: Isoenzymes are vital in diagnostics since they help pinpoint diseased organs in the body.
  • LDH Isoenzymes and Diseases:
    • LDH 1 & 2: Raised in myocardial infarction (heart attack), leukemia, and blood diseases.
    • LDH 3: Elevated due to leukemia.
    • LDH 4 & 5: High levels may indicate viral hepatitis (liver disease).
  • CK Isoenzymes and Diseases:
    • CK-BB: Increased activity points to brain tumors.
    • CK-MB: Raised levels in myocardial infarction (heart attack).
    • CK-MM: Elevated levels indicate skeletal muscle problems (e.g., muscle dystrophy).
  • Other Plasma Enzymes and Diseases:
    • SGPT/ALT (Alanine Transaminase): Indicates liver conditions.
    • SGOT/AST (Aspartate Transaminase): Indicates liver, heart problems, and obstructive liver disease.
    • Alkaline Phosphatase: Associated with bone and prostate conditions.
    • Acid Phosphatase: Associated with different diseases, including prostate cancer.
    • Amylase: Important for pancreatitis diagnosis.
    • Lipase: Also pivotal in diagnosing pancreatitis.

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