In what part of a eukaryotic or
prokaryotic cell does glycolysis take place?
This question is asking about
glycolysis, the first stage of cellular respiration. To answer it, let’s review the key
facts of cellular respiration and where in the cell it occurs.
All organisms use nutrients,
usually glucose, for energy. Some, like plants, make their own
nutrients, and others, like us, eat them. But all use a process called
cellular respiration to break them down to release energy, which is then transferred
to adenosine triphosphate, ATP. Adenosine triphosphate — tri- means
three, so ATP contains three phosphate groups — then stores this energy until it is
needed by the organism to power metabolic reactions or to carry out essential
processes like digestion, breathing, and movement.
Now that we understand the purpose
of cellular respiration, let’s look more closely at the process of glycolysis.
Glycolysis is the first stage of
both aerobic and anaerobic cellular respiration. During the process of glycolysis,
two molecules of the three-carbon molecule pyruvate are produced from one molecule
of the six-carbon glucose. There is a net production of two
adenosine triphosphate molecules, which, as we’ve just seen, are important for
energy storage. Two molecules of reduced NAD are
also produced, which are used in a later stage of cellular respiration.
The whole process takes place in
the cytoplasm of both prokaryotes and eukaryotes. Then, if oxygen is present, the
pyruvate molecules will be transferred into the mitochondria to complete the aerobic
respiration of glucose, aerobic meaning with oxygen. If oxygen is not available, the
pyruvate stays in the cytoplasm for the completion of anaerobic respiration, an-
Now that we have reviewed these key
points about cellular respiration, and in particular glycolysis, let’s return to our
question. We can now give the correct
answer. The part of the eukaryotic or
prokaryotic cell where glycolysis takes place is a cytoplasm.