This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
Respiratory burst in neutrophils occurs due to 
Select and explain. 
A. NADPH oxidase, B. NADP oxidase, C. FADH2 oxidase, D. FAD
A: NADPH oxidase
Answer: A: NADPH oxidase 
Explanation: When the cell membrane-bound enzyme NADPH oxidase is activated, with the production of toxic oxygen metabolites. The combination of the toxic oxygen metabolites and the proteolytic enzymes from the granules makes the neutrophil a very effective killing machine. Activation of NADPH oxidase is associated with a sharp increase in O2 uptake and metabolism in the neutrophil (the respiratory burst) and generation of O2- by the following reaction: NADPH + H+ + 2O2+ - NADP+ + 2H++ 2O2- O2- is a free radical formed by the addition of one electron to O2.Ref: Ganong's Review of Medical Physiology Twenty-Third Edition Page no: 64