as Liebig's chemical theory. He formulated his own theory arguing that the production of alcohol was not a biological process but a chemical process. It disputed the idea that fermentation could happen due to microscopic organisms like the yeast as previously contested by Schwann. Liebig assumed that activities coming from the decomposition of organic matter would proceed to the conversion of sugar to carbon dioxide and alcohol only. Then in the middle of 18th Century, Louis Pasteur opposed Liebig' chemical theory. In Pasteur's experiment, he showed that fermentation is highly dependent on the bodily functions that occur in bacteria and in living yeast cells, He wrote that "alcoholic fermentation (Figure 2.4 is an act associated with the life and organization of the yeast cells, not with the death or putrefaction of the cells" themselves." He was highly recognized due this work. From here, the view on the chemistry of life can be distinguished from the chemistry of nonliving things. From this point of view of the gelatinous and homogenous structure of matter in organisms known as the protoplasm (living part of the cell), do all the intracellular processes. These processes include respiration, biosynthesis and decomposition. In spite of all the hullabaloo of vitalism and fermentation, a major substance from animals and plants was identified. It is composed of carbon, hydrogen oxygen and nitrogen and it was now known as "Protein", which means the most important thing. The term was first used in 1838. Then from 1850s-1890s, carbohydrates, lipids, and nucleic acids were also recognized. From here, the term "biochemistry" was coined in the 1870s. In addition to the components within the protoplasm, Friedrich Miescher was able to identify " nuclein", the entit inside the nuclei of leukocytes (human white blood cells) Moreover, in 1878, a German physiologist named Wilhelm Kühne coined the term enzyme, which comes from Greek Ev¿uov "in leaven", to describe the process. Later on, the word enzyme refers to nonliving substances such as pepsin, and the word ferment used to refer to chemical activity produced by living organisms. Then in 1897, "Eduard Buchner (Figure 2.5) began to study the ability of yeast extracts to ferment sugar despite the absence of living yeast cells. In a series of experiments at the University of Berlin, he found that the sugar was fermented even when there were nO living yeast cells in the mixture https://www.nobelprize.org/prizes/chemistry/1907/buchner/biographical/.He named the the fermentation of sucrose enzyme that brought about as "zymase" https://www.nobelprize.org/uploads/3018/06/buchner-lecture.pdf. In 1907 he received the "for his biochemical research and his discovery of cell-free Nobel Prize in Chemistry fermentation" (http://nobelprize.org).Following Buchner's example;,enaymes are usually named according to the reaction they carry out. Typically the suffix -ase is added to the name of the substrate (e.g., lactase is the enzyme that cleaves lactose) or the type of reaction (e.g., DNA polymerase forms DNA polymers). In the early 20th Century, 1903 in particular, the term "Biochemistry" was officially coined by the German chemist Carl Neuberg. from Greek words, bios (= life) and chymos juice). Having presented that enzymes could function outside a living cell, the next step was to determine their biochemical nature. Many early workers noted that enzymatic activity was associated with proteins, but several scientists (such as Nobel laureate Richard Willstätter) argued that proteins were merely carriers for the true enzymes and that proteins per se were incapable of catalysis. However, in 1926, James B. Sumner showed that the enzyme urease was a pure protein and crystallized it; Sumner did likewise for the enzyme catalase in 1937. The conclusion that pure proteins can be enzymes was definitively proved by Northrop and Stanley, who worked on the digestive enzymes pepsin (1930), trypsin and chymotrypsin. These three scientists were awarded the 1946 Nobel Prize in Chemistry This discovery that enzymes could be crystallized eventually allowed their structures to be solved by x-ray crystallography. This was first done for lysozyme, an enzyme found in tears, saliva and egg whites that digests the coating of some bacteria; the structure was solved by a group led by David Chilton Phillips and published in 1965(Blake CC). This high-resolution structure of lysozyme marked the beginning of the field of structural biology and the effort to understand how enzymes work at an atomic level of detail. Question: Identify three enzymes and the scientists who worked on them. What are the importance of these enzymes?