A bacterium was grown in two test tubes filled with media rich in glucose. One tube was sealed to produce anaerobic conditions, and the other was not. A third uninoculated, unsealed tube was used as a control. Glucose utilization by this bacterium causes acid production, which is indicated by a lightening of the media color. If the bacterium is able to produce ATP only by aerobic respiration, we expect lightening of media in .

unsealed tube only.

Explanation:

Oxygen is the combustion fuel of glucose in cellular respiration.It is the final electron acceptor  in the process of oxidative phosphorylation , needed for ATPs synthesis in the bacteria.

In its absence as in sealed tube, ATP synthesis will not occur because the electron transport chain needed  to generate Proton Motive Force(PMF) , to pump protons  into membranes for electrochemical gradients  needed to supply energy for  Enzyme ATPase to synthesized ATPs is missing. The oxygen must  accept the electrons to create gradients for the ETC

.

Therefore it is only under aerobic medium, unsealed tube, that it  lightening must occur.Besides the control tube is not inoculated.

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