What role do coenzymes like NAD+ and FAD play in cellular respiration?
A They are electron carriers that facilitate redox reactions.
B They are the main source of ATP production.
C They act as enzymes to speed up reactions.
D They provide structural support to mitochondria
The correct answer and explanation is:
The correct answer is: A) They are electron carriers that facilitate redox reactions.
Coenzymes like NAD+ (Nicotinamide adenine dinucleotide) and FAD (Flavin adenine dinucleotide) play a critical role in cellular respiration, primarily in the process of redox reactions. These coenzymes serve as carriers of electrons and hydrogen ions, which are essential for the transfer of energy within cells.
During cellular respiration, glucose is broken down in several stages: glycolysis, the citric acid cycle, and the electron transport chain. NAD+ and FAD are involved in the first two stages of respiration, where they accept electrons and hydrogen atoms from metabolites like glucose. Specifically, NAD+ is reduced to NADH, and FAD is reduced to FADH2. These reduced forms of the coenzymes (NADH and FADH2) then carry the electrons to the electron transport chain (ETC), which is located in the mitochondria.
In the electron transport chain, the electrons are transferred through a series of protein complexes. As they move through the chain, energy is released and used to pump protons across the mitochondrial membrane, creating an electrochemical gradient. This gradient powers the enzyme ATP synthase, which synthesizes ATP, the primary energy currency of the cell.
Ultimately, NAD+ and FAD are crucial for the efficient production of ATP, but their primary role is as electron carriers, facilitating the redox reactions that release energy for ATP synthesis. Without these coenzymes, cellular respiration would not be able to efficiently transfer energy and produce the ATP needed for cellular functions.