The dotted line most likely represent C NADH and FADH2
Explanation:
NADH is a reducing agent formed during glycolysis and TCA cycle. FADH2 also act as electron donor or reducing equivalent generated only during TCA cycle.
NADH and FADH2 are reduced form of coenzyme NAD+ and FAD. NADH and FADH2 formed during glycolysis or TCA cycle, enters into the electron transport chain(ETC) to perform oxidative phosphorylation that deals with reduction of oxygen(O2) to water(H2O) along with the formation of energy in form of ATP.
Enzymes help speed up chemical reactions in the human body. They bind to molecules and alter them in specific ways. They are essential for respiration, digesting food, muscle and nerve function, among thousands of other roles.