Energy is released to be used by a cell when a phosphate group is <u><em>Removed from ATP to form ADP.</em></u>
Answer: <em>C. Removed from ATP to form ADP
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Explanation:
Three important energy carrier molecules in a cell are: ATP (Adenosine triphosphate, NADPH (Nicotinamide Adenosine Dinucleotide Phosphate) and FADH2. All the three carrier molecules play an important role in cellular respiration and photosynthesis.
One NADH molecule is equal to 3 ATP molecule while 1 FADH2 molecule is equal to 2 ATP molecule. During the active process, ATP is used as a form of energy because ATP dephosphorylates to ADP and Inorganic phosphate, Pi and release energy.
