Question

The net energy yield from this pathway, where glucose is broken down through several steps forming pyruvate, is ________ molecules of ATP and _____ molecules of NADH.

Answer 1

Answer:

2 molecules of ATP and 2 molecules of NADH

Explanation:

Glycolysis is the first step of cellular respiration (break down of glucose to extract energy) which occurs in the cytoplasm. Glycolysis is a pathway common to all living organisms- prokaryotes and eukaryotes, as it does not require oxygen to occur.

Glycolysis occurs in two major phases (ten steps) requiring 10 enzymes catalyzing each step; the energy-requiring phase and the energy-requiring phase.

In the energy-requiring phase, the starting molecule (glucose) gets rearranged in a series of chemical reactions, and two phosphate groups gets attached to it producing fructose-1,6-bisphosphate which is unstable, This modified sugar then splits in half due to its instability to form two different but inter-convertible phosphate-bearing three-carbon sugars (Dihydroxyacetonephosphate, DHAP and Glyceraldehyde-3-phosphate, G3P). Because the phosphates used in these steps come from 2 ATP molecules, 2 ATP molecules get used up in this phase

All the DHAP molecules get converted to G-3-P in order to enter the next phase.

In the energy-recovering phase, the 3-carbon sugar (G3P) is converted into another three-carbon molecule called pyruvate, through a series of reactions. In these reactions, two ATP and 1 NADH molecules are made. This recovery phase occurs twice (one for each of the two isomeric three-carbon sugars, DHAP and G3P). Hence, a total of 4 ATP and 2 NADH molecules are produced in this phase.

Overall, Glycolysis converts one glucose (six-carbon) molecule to two pyruvate (three-carbon) molecules and a net release of 2 ATP molecules (4 overall - 2 used) and 2 NADH molecules.