10 years old Ramu has increasing muscle weakness and raised CPK levels. The most likely defect is in plasma membrane of-

Ans. is 'b' Muscle fibres (Ref. Chandrasoma Taylor, 3/e, p. 953).Increase in CPK level with muscle weakness suggests muscle cell damage.Creatine kinase is an enzyme found mainly in:Skeletal muscle*Heart*Brain*Its levels will be raised in the serum when any of the above mentioned cell is damaged.There are various isotypes of the enzyme which are specific for difference cells.Enzyme - TissueCreatine kinase - Heart*(MB isoenzyme)Creatine kinase - Brain*(BB isoenzyme)Creatine kinase - Skeletal muscle*(MM isoenzyme)Other enzymes elevated in muscle diseasesAldolase*Aminotransferases specially (ACT) *Lactate dehydrogenase*