Question

why is oxygen is needen in cellular respiration?

Answer 1

CAN ALSO BE ANAEROBIC

Answer 2

IT IS USED TO OXIDIZE A SUGAR MOLECULE IN AEROBIC RESPIRATION

Answer 3

TO RELEASE ATP CO2 AND H2O

Answer 4

Strictly, speaking, it's not, but... in the aerobic part of cellular respiration, it's used as the terminal electron acceptor in the electron transport chain.

Answer 5

Sorry, @katragaddasaichandra, but it's not that simple! Glucose is broken down in a whole bunch of different steps in glycolysis (which does not require oxygen), and under aerobic conditions, the resulting molecule (pyruvate) is then modified a bit and fed into the citric acid cycle (in the mitochondria), where it's oxidised through even more steps to become CO2. During the citric acid cycle, you get several molecules of NADH and FADH2, which are then used to feed electrons into the electron transport chain. The electron transport chain involves protein complexes embedded in one of the mitochondrial membranes, and this is the step that generates the most ATP for the cell. It is ALSO the step that requires oxygen.

Answer 6

Have to agree with @Calliope. Oxygen's primary purpose in respiration is as a final electron acceptor in the ETC or electron transport chain. The step that initially breaks up glucose into smaller carbon molecules called pyruvate is possible with out without oxygen and is common to both aerobic and anaerobic respiration.