Video Transcript
What is the role of reduced NAD and
FAD in the electron transport chain? (A) To act as the final electron
acceptor. (B) To actively transport hydrogen
ions across the mitochondrial membrane. (C) To provide the energy to
phosphorylate ADP to form ATP. (D) To provide electrons for the
electron transport chain.
The electron transport chain refers
to a series of protein complexes including cytochromes, enzymes, and coenzymes that
are specialized to transport electrons. The electron transport chain is
found within the inner membrane of mitochondria. Let’s have a look at the electron
transport chain in a bit more detail. We can see in the diagram that
electrons move between protein complexes in the chain before eventually leaving and
joining with hydrogen ions and oxygen to form water. As electrons move through the
electron transport chain, free energy is released. This energy is used to actively
transport hydrogen ions across the membrane, out of the matrix, and into the
intermembrane space.
But what about reduced NAD and
reduced FAD? Where do they come into this? In chemistry, when we say that
something is reduced, we mean it has gained electrons. NAD and FAD become reduced in the
preceding stage of respiration, the Krebs cycle. When they enter oxidative
phosphorylation, reduced NAD and FAD donate their electrons to the electron
transport chain.
Let’s go through these reactions
together now. During the reactions, their
hydrogen atoms disassociate. This means that the atoms split
into positively charged ions and negatively charged electrons. The electrons now move along the
electron transport chain, and hydrogen ions are actively transported across the
inner mitochondrial membrane. Due to the electrochemical gradient
produced, the enzyme ATP synthase can use the movement of hydrogen ions back into
the matrix to produce ATP.
So now we can accurately describe
the role of reduced NAD and reduced FAD in the electron transport chain. Our correct answer is (D) to
provide electrons for the electron transport chain.
