Oxidoreductases, decarboxylases, and dehydrogenases are key enzymes involved in cellular respiration. Oxidoreductases transfer electrons, hydrogen, or oxygen between molecules. Decarboxylases catalyze reactions that remove carbon dioxide from molecules, such as in anaerobic respiration. Dehydrogenases remove hydrogen from molecules, as seen in the Krebs cycle, and their activity can be measured using artificial hydrogen acceptors like TTC.