Question

oxygen is necessary for complete oxidation of glucose give reason

Answer 1

Aerobic oxygen is the process by which the metabolism of sugar and fatty acids take place in the presence of oxygen to produce giving energy ATP. Looking at the reaction of oxidation of glucose, we see that glucose is oxidized in the presence of oxygen. 
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Answer 2

Answer:

Glucose can be used by two pathways i.e. aerobic and anaerobic respiration. Glucose is completely oxidised only in the presence of oxygen and results in the release of energy. It undergoes three steps to finally reach its fate - glycolysis, Kreb's cycle and electron transport chain reaction. In anaerobic respiration, glucose undergoes partial oxidation and results in the release of energy which is comparitvely less to the energy released during aerobic respiration.