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← Theoretical 2

Q75 — Plasma Enzyme Diagnostics After Myocardial Infarction

Theoretical 2 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Cardiovascular Physiology

Measurement of blood plasma enzymes allows precise diagnosis of some diseases. Creatine kinase (CK), lactate dehydrogenase (LDH) and β-hydroxybutyrate dehydrogenase (β-HBDH) were measured in the blood of a patient with acute chest pain. Additionally, electrophoretic separation of creatine kinase isoforms was performed. Creatine kinase is an enzyme composed of two subunits, the brain-typical subunit B and the muscle-typical subunit M, encoded by different genes. Different tissues have different isoforms of the enzymes: BB occurs in the brain, MB in the heart muscle and MM in skeletal muscles.

Two-panel figure. Image 1: change in enzyme activity (relative to norm after infarction) over the days following a myocardial infarction, with curve 1 (CK) rising sharply and peaking around day 1 before falling back to normal by about day 3-4, curve 2 (LDH) peaking more gradually around day 4-5 and declining slowly, and curve 3 (β-HBDH) declining the most slowly, still above normal by day 16. Image 2: electrophoretic separation of CK isoforms showing a large MM peak and small MB peak in a healthy individual (a), versus a large MM peak and a clearly larger MB peak in a patient following myocardial infarction (b). Image 1: change in the activity of enzymes after myocardial infarction (1-CK, 2-LDH, 3-β-HBDH). Image 2: isoforms of CK in blood plasma; (a) a healthy individual, (b) a patient following myocardial infarction.

Based on this biochemical analysis, determine whether the following statements are true or false.

A. Elevated levels of CK, LDH and β-HBDH in the plasma can be caused by tissue and cell damage due to pathological conditions.
B. The rapid rise in CK activity, 24-48 hours after the emergence of pain, points to the developing dystrophy in the skeletal muscles of the chest.
C. The three- to four-fold increase in the activity of the MB isoenzyme is caused by the developing damage to the heart muscle.
D. All enzymes discussed, i.e. CK, LDH and β-HBDH, participate in the energy supply in muscles.
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Question reproduced from IBO 2022, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)