Question

We have discussed fermentation as a mechanism for regeneration of NAD for glycolysis under conditions when an ETC is not available for NAD regeneration. Embden-Meyerhof glycolysis converts one NAD to NADH for each molecule of pyruvate produced. Fermentation of pyruvate to propionic acid converts one NADH to NAD for each molecule of pyruvate fermented. Which of the following statements is TRUE of metabolism under conditions that force the use of pyruvate fermentation to propionate?

It should be possible to perform both Embden-Meyerhof glycolysis and run the Krebs cycle under these conditions.

Enzymes that ferment pyruvate to propionate are expressed under all conditions of growth

An appropriate electron acceptor for ETC is lacking under these conditions.

Regeneration of NAD occurs by reduction of NADH

Answer 1

An appropriate electron acceptor for ETC is lacking under these conditions.

Propionic acid bacteria (also known as propionibacteria) are Gram-positive, anaerobic bacteria that means that they are unable to use oxygen as a terminal electron acceptor in the ETC.