Question

The pentose phosphate pathway (PPP) is localized to the cytosol.

Answer 1

Answer: The pentose phosphate pathway (PPP) is localized to the cytosol because fatty acid synthesis uses the NADPH generated by the PPP.

Explanation:

The pentose phosphate pathway is mainly catabolic and provides an alternative glucose oxidizing pathway for the generation of NADPH that is required for reductive biosynthetic reactions such as those of cholesterol biosynthesis, bile acid synthesis, steroid hormone biosynthesis, and fatty acid synthesis.

Fatty acid biosynthesis occurs in the cytosol and requires the reducing equivalent NADPH in large amounts. The main source of generating NADPH in animal cells, the pentose phosphate pathway is therefore, localized in the cytosol in order to furnish a strongly reducing environment for fatty acid biosynthesis to proceed.