Question

Which group of scientists discovered glycolysis?
(a) Embden, Merrison, and Pitches
(b) Embden, Meyerhof, and Parnas
(c) Emerson, Hoffman, and Peterson
(d) Avery, Macleod, and McCarthy

Answer 1

The groups of three scientists worked in unity to elucidate the pathway of glycolysis in 1940 while working on muscle extracts. Glycolysis is the first step common to both aerobic and anaerobic respiration.

Complete answer:
Glycolysis is a ten-step pathway that occurs in the cytoplasm of the cell. In Glycolysis, 6-Carbon molecule glucose is oxidized to two 3-Carbon molecules of pyruvate whose scheme was given by Gustav Embden, Otto Meyerhof, and J Parnas, and thus, is also known as the EMP pathway. It is grossly divided into two phases i.e preparatory phase and pay-off phase.
- The energy is invested or consumed in the preparatory phase, while in the payoff phase, energy is released.
- In the preparatory phase, glucose is phosphorylated by ATP to produce glucose-6-phosphate which isomerizes to fructose-6-phosphate.
- Another phosphorylation by ATP leads to the production of fructose-1,6-bisphosphate from fructose- 6-phosphate.
- Fructose-1,6-bisphosphate is cleaved to produce two 3-C molecules. These are glyceraldehyde- 3-phosphate and dihydroxyacetone phosphate.
- Dihydroxyacetone phosphate isomerizes to create Glyceraldehyde-3-phosphate. With this, the preparatory phase ends.
- The pay-off phase begins with the two molecules of Glyceraldehyde-3-phosphate converted to release 1,3- bisphosphoglycerate catalyzed by dehydrogenase coupled with the release of NADH.
- A high energy phosphate group is transferred from 1,3- bisphosphoglycerate to ADP. This leads to the generation of ATP and 3-phosphoglycerate.
- Isomerization of 3-phosphoglycerate to 2-phosphoglycerate is forwarded by the removal of a water molecule to release phosphoenolpyruvate.
- Glycolysis ends with an irreversible step of generation of ATP and the end product ‘pyruvate.’
So, the correct answer is ‘(b) Embden, Meyerhof, and Parnas’.

Note:
- The product ‘pyruvate’ is further oxidized into acetyl-CoA. In eukaryotes, this reaction takes place in the matrix of mitochondria.
- Pyruvate is a charged molecule and thus requires a transport protein to enter mitochondria.
- Production of acetyl-CoA is the junction between glycolysis and the next step of aerobic respiration i.e Krebs cycle.