Metabolic Pathways has been compared
to roadways as depicted on road maps.
And if thats the case on
the Pentose Phosphate Pathway
is gonna be one of the more interconnective
roadways that we find inside of cells.
The Pentose Phosphate Pathway
is a very important component
of carbohydrate metabolism
having multiple inputs and outputs
as we shall see.
Two of the steps of the Pentose Phosphate
Pathway are oxidated in nature.
And they synthesize about
60% of the cells NADPH.
NADPH of course is necessary for making
bigger and important molecules.
The Pentose Phosphate Pathway generates
intermediates for other pathways as well.
The very important one is Ribose- 5 phosphate
which is needed for making nucleotides.
Erythrose-4 phosphate is necessary
for making aromatic amino acids
and aromatic amino acid metabolism.
NADPH is I know that it is something
this important for synthesizing
of fatty acids and other molecules
of the cell may need.
NADPH is also needed to keep the
important antioxidant glutathione reduced
and protect the cell from
reactive oxygen species.
So, it contains numerous intermediates
of glycolysis and gluconeogenesis
and this provides for a lot of the
pathways flexibility as we shall see.
Now, one of the enzymes of
the Pentose Phosphate pathways
is also used in the Calvin Cycle
and it’s known as transketolase.
And important thing to realize about
the Pentose Phosphate pathway is that
unlike the way it’s commonly thought,
the pathway doesn’t really have a start or an end.
You will see end points but those end points
are connected to other pathways
and there are multiple points
of the entry into the pathway
and we’ll see some examples of that.
The Pentose Phosphate pathway occurs
exclusively in the cytoplasm of cells.
The ten intermediates of the Pentose Phosphate
Pathway are depicted in this figure.
And I put them in the several groups
based upon their sort of commonality.
The first group are three intermediates
from the pathway of glycolysis.
Glucose-6 phosphate, Fructose-6 phosphate
and Glyceraldehyde-3 phosphate.
The next two intermediates
are important in other pathways
Ribose- 5 phosphate, this I know
for nucleotide metabolism
and Erythrose-4 phosphate
for making aromatic amino acids.
The next three are irrelatively
unusual relatively rare sugars
that aren’t found too much outside
the Pentose Phosphate pathway and include
Ribulose-5 phosphate, Xylulose-5 phosphate
and Sedoheptulose-7 phosphate.
And the last two are sugar derude is that pretty much
found only in the Pentose Phosphate pathway.