Answer:
Recycles NAD+ molecules for
glycolysis.
Explanation:
First and foremost,it is important to understand what cellular respiration and fermentation are:
Cellular respiration is a set of metabolic reactions and processes
that take place in the cells of organisms to convert chemical energy
from oxygen molecules or nutrients into adenosine triphosphate
(ATP), and then release waste products AND
Fermentation is:
Any energy-releasing metabolic process that takes place only
under anaerobic conditions (becoming more scientific). OR
Any metabolic process that releases energy from a sugar or
other organic molecule, does not require oxygen or an electron
transport system, and uses an organic molecule as the final
electron acceptor.
Back to the role of fermentation in cellular respiration and what it recycles:
Without oxygen, pyruvate ( pyruvic acid) is not metabolized by
cellular respiration but undergoes a process of fermentation. The
pyruvate is not transported into the mitochondrion, but remains in
the cytoplasm, where it is converted to waste products that may be
removed from the cell. This serves the purpose of oxidizing the
electron carriers so that they can perform glycolysis again and
removing the excess pyruvate. Fermentation oxidizes NADH to NAD +
so it can be re-used in glycolysis. In the absence of oxygen,
fermentation prevents the buildup of NADH in the cytoplasm and
provides NAD + for glycolysis.
