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Glycolysis is the first pathway most NEET students learn in respiration, and NCERT tells you it is called the EMP pathway after Gustav Embden, Otto Meyerhof and J. Parnas. That is usually all students hear about Meyerhof. His story shows how careful bookkeeping of a few chemicals in a frog's muscle led to one of the central maps in biology. This post covers the experiment, a worked example of his key ratio, and the habit worth copying.
Who was Otto Meyerhof?
The Nobel Prize biography records that Otto Fritz Meyerhof was born on 12 April 1884 in Hannover and grew up in Berlin. He trained in medicine, graduating in 1909 with a thesis on a psychiatric subject, and wrote on psychology and philosophy. Under the influence of Otto Warburg, then at Heidelberg, he turned to cell physiology. He moved to Kiel in 1912.
In 1924 he joined the Kaiser Wilhelm institutes in Berlin-Dahlem, and in 1929 he took charge of the new Kaiser Wilhelm Institute for Medical Research in Heidelberg. In 1938 conditions in Germany became too difficult and he left for Paris. In 1940, when the Nazis invaded France, he fled again, through Spain, to the United States, where the University of Pennsylvania created a research professorship for him. The Nobel facts page gives his death as 6 October 1951 in Philadelphia.
What question was he trying to answer?
The 1922 presentation speech sets out the puzzle. Muscle can convert 20 to 30 percent of its chemical energy into work, which rules out a heat engine at body temperature. A. V. Hill, who shared the prize, had shown with sensitive heat measurements that a muscle's twitch itself does not need oxygen, and that a delayed burst of heat during recovery appears only when oxygen is present. Earlier, Fletcher and Hopkins had shown that muscle forms lactic acid and removes it again in oxygen. The open question was where the lactic acid went.
What did Meyerhof measure?
He measured two things at the same time in recovering frog muscle: how much lactic acid disappeared and how much oxygen was consumed. The speech reports that the oxygen used corresponded to no more than one third to one quarter of the lactic acid removed. Most of it was not being burned.
He also tracked carbohydrate. When lactic acid built up, an equal amount of carbohydrate, mainly glycogen, disappeared. When lactic acid vanished, carbohydrate returned, by the amount not accounted for by oxygen. His scheme: of every four molecules of lactic acid, one is oxidised and three are turned back into carbohydrate.
Can you check the one-in-four ratio?
Use clearly hypothetical sample numbers. Suppose a recovering muscle removes 20 µmol of lactic acid (C3H6O3).
Burning lactic acid: C3H6O3 + 3O2 → 3CO2 + 3H2O. Check atoms: carbon 3 = 3, hydrogen 6 = 6, oxygen 3 + 6 = 9 on the left and 6 + 3 = 9 on the right.
If all 20 µmol were burned, oxygen needed = 20 × 3 = 60 µmol.
Meyerhof's ratio says only one in four is burned: 20 ÷ 4 = 5 µmol, needing 5 × 3 = 15 µmol of oxygen.
The other 15 µmol is rebuilt. Since one glucose unit gives two lactic acid molecules, that is 15 ÷ 2 = 7.5 µmol of glucose units.
Oxygen used compared with the full-burn amount: 15 ÷ 60 = 1/4, matching the range of one third to one quarter he reported.
How did this lead to the steps of glycolysis?
His Nobel biography credits him with a potassium chloride extract of muscle that could carry out all the steps of glycolysis, given glycogen, hexose diphosphate and hexokinase from yeast. In 1925 he extracted the glycolytic enzyme system from muscle, and his group reconstructed the main steps from glycogen to lactic acid, confirming and extending a scheme proposed by Gustav Embden in 1932. His associate Lohmann isolated adenosine triphosphate (ATP).
NCERT Class 11, Chapter 12 (Reprint 2026-27) describes glycolysis as ten enzyme-controlled reactions in the cytoplasm that turn glucose into pyruvate. ATP is used at two steps, glucose to glucose 6-phosphate and fructose 6-phosphate to fructose 1,6-bisphosphate, and made at two steps, BPGA to PGA and PEP to pyruvate. Since one glucose gives two three-carbon molecules, ATP made directly is 2 × 2 = 4, so the net gain is 4 − 2 = 2. NCERT also notes that in exercising muscle short of oxygen, pyruvate is reduced to lactic acid. Glycolysis is in the NEET-UG 2026 syllabus; check the current year's version.
Common mistakes:
Calling lactic acid pure waste. Meyerhof showed most of it is rebuilt into carbohydrate.
Forgetting the P in EMP. It stands for Parnas.
Counting 4 ATP as the net yield of glycolysis. Subtract the 2 used.
What can a student take from Meyerhof?
Meyerhof came to biochemistry from medicine and philosophy, and he kept careful accounts: every molecule that disappeared had to turn up somewhere. That habit works on exam numericals too. When a respiration question gives you quantities, write a balance sheet before you calculate. To practise that kind of question, the Fermi Problem Library has a step-by-step solver that explains the reasoning rather than printing an answer.
Try it: redo the worked example for 36 µmol of lactic acid and check that the oxygen ratio still comes out at one quarter.
