Final answer:
NADH and FADH2 are the reduced forms of NAD and FAD, respectively, and are essential in energy transfer during ATP synthesis.
Step-by-step explanation:
Which of the following are reduced coenzymes? The correct answer is c. NADH and FADH2. Oxidation-reduction reactions involve enzymes that facilitate the removal of hydrogen atoms, and coenzymes play a pivotal role in these reactions by accepting hydrogen atoms. Nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD) are notable coenzymes in these reactions. When they accept hydrogen atoms, NAD is converted to NADH and FAD to FADH2, forming their respective reduced forms. These energy-rich molecules, NADH and FADH2, are critical for the transfer of energy during ATP synthesis.