Final answer:
The isoenzyme for brain and lung cells is CPK-BB. CPK, also known as creatine phosphokinase, exists in various isoenzyme forms, with the two polypeptides 'B' and 'M' forming different combinations to give rise to three isoenzymes of CPK. The isoenzyme CPK-BB is predominant in brain and lung cells.
Step-by-step explanation:
Creatine phosphokinase (CPK) is an enzyme that catalyzes the conversion of creatine to creatine phosphate, which is crucial for supplying energy during muscle contraction. CPK has two subunits, 'B' (brain type) and 'M' (muscle type), and these combine to form three distinct isoenzymes.
- CPK-BB: Predominantly found in the brain.
- CPK-MM: Predominant in skeletal muscle.
- CPK-MB: Predominantly found in the cardiac muscle.
The CPK-BB isoenzyme is the one primarily found in brain and lung cells, making option 1) CPK-BB the correct answer to the question, 'What is the isoenzyme for brain and lung cells?'