pentoosifosfaattireitillä

The pentose phosphate pathway, known in Finnish as pentoosifosfaattireitti, is a fundamental metabolic process that occurs in the cytoplasm of cells. It is an alternative route for glucose metabolism, distinct from glycolysis and the citric acid cycle. The pathway's primary functions are to generate NADPH, a crucial reducing agent for biosynthetic reactions and antioxidant defense, and to produce pentose sugars, such as ribose-5-phosphate, which are essential for nucleotide and nucleic acid synthesis.

The pentose phosphate pathway has two main phases: the oxidative phase and the non-oxidative phase. The oxidative phase involves the irreversible conversion of glucose-6-phosphate into ribulose-5-phosphate, generating two molecules of NADPH in the process. This phase is particularly important for cells that require a high supply of NADPH, such as red blood cells for combating oxidative stress and liver cells for fatty acid synthesis.

The non-oxidative phase, on the other hand, is a reversible series of reactions that interconverts various sugar phosphates. This phase can produce ribose-5-phosphate, which is then used for DNA and RNA synthesis. Alternatively, the products of the non-oxidative phase can be fed back into glycolysis, allowing for the complete oxidation of glucose when NADPH production is not the primary need. The pentose phosphate pathway is thus a dynamic pathway that adapts its output based on the cell's metabolic requirements.