Video Transcript
What is the net yield of ATP for
one glucose molecule undergoing glycolysis?
Glycolysis is the first stage of
cellular respiration. Glycolysis takes place in the
cytoplasm of cells of nearly all living organisms, and it happens whether oxygen is
present or not. In glycolysis, a molecule of
glucose undergoes a series of biochemical reactions to form two molecules of
pyruvate or pyruvic acid. In the first set of reactions in
glycolysis, two molecules of ATP are actually used to convert glucose into the
phosphorylated sugar fructose-1,6-bisphosphate. So, currently, the yield of ATP is
minus two.
Next, the six-carbon
fructose-1,6-bisphosphate is split into two three-carbon compounds. This reaction does not use any ATP,
but it also does not produce any ATP. So our current yield of ATP still
stands at minus two. Finally, the two three-carbon
compounds need to be converted into our final product, pyruvate. In this reaction, the three-carbon
compounds donate a hydrogen ion and two electrons to a coenzyme called NAD+ to form
reduced NAD or NADH. This reaction is coupled to another
reaction.
Using the energy from the reduction
of NAD+, G3P gains another phosphate group. This new compound doesn’t last long
though. Following this, G3P loses both of
its phosphate groups. These phosphate groups are gained
by two molecules of ADP to form ATP. For each molecule of pyruvate
formed, two molecules of ATP are produced. Because there are two molecules of
pyruvate, four molecules of ATP are produced in total. So our yield of ATP before this
stage was minus two, and here we have produced four molecules of ATP.
Now, we’re ready to calculate the
net yield of ATP. Minus two ATP plus four ATP gives
us a net yield of two ATP. So, for each single molecule of
glucose that undergoes glycolysis, the net yield of ATP is two molecules.
