<prompt> 10 years old Ramu has increasing muscle weakness and raised CPK levels. The most likely defect is in plasma membrane ofNervesMuscle fibresBasement membraneAll body cells  <response>: Increase in CPK level with muscle weakness suggests muscle cell damage.Creatine kinase is an enzyme found mainly in Skeletal muscle, Heart, BrainIts 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 MB isoenzyme HeartCreatine kinase BB isoenzyme BrainCreatine kinase MM isoenzyme Skeletal muscleOther enzymes elevated in muscle diseases Aldolase, Aminotransferases specially ACT, Lactate dehydrogenase 