his study on proteins. In 1910 he received the Nobel
Prize in physiology or medicine for his contributions in
cell chemistry and work on proteins.
Among his important publications are Unter-
suchungen über die Nukleine und ihre Spaltungspro-
dubte (Investigations into the nucleins and their
cleavage products), 1881; Die Gewebe des mensch-
lichen Körpers und ihre mikroskopische Untersuchung
(The tissues in the human body and their microscopic
investigation), 1889–91, in two volumes, with Behrens
and Schieerdecker; and the Leitfaden für medizinisch-
chemische Kurse (Textbook for medical-chemical
courses), 1888. He was also the author of Die Prob-
leme der Biochemie(The problems of biochemistry),
1908; and Die Beziehungen der Chemie zur Physiolo-
gie(The relationships between chemistry and physiol-
ogy), 1913.
Kossel had honorary doctorates from the Universi-
ties of Cambridge, Dublin, Ghent, Greifswald, St.
Andrews, and Edinburgh, and he was a member of var-
ious scientific societies, including the Royal Swedish
Academy of Sciences and the Royal Society of Sciences
of Uppsala. Albrecht Kossel died on July 5, 1927.
Krebs, Sir Hans Adolf(1900–1981) German/British
Biochemist Sir Hans Adolf Krebs was born at
Hildesheim, Germany, on August 25, 1900, to Georg
Krebs, M.D., an ear, nose, and throat surgeon of that
city, and his wife Alma (née Davidson).
Krebs was educated at the Gymnasium Andreanum
at Hildesheim. Between 1918 and 1923 he studied
medicine at the Universities of Göttingen, Freiburg-
im-Breisgau, and Berlin. He received a M.D. degree at
the University of Hamburg in 1925. In 1926 he was
appointed assistant to professor Otto Warburg at the
Kaiser Wilhelm Institute for Biology at Berlin-
Dahlem, where he remained until 1930. He was
forced to leave Germany in 1933 because of his Jew-
ish background.
In 1934 he was appointed demonstrator of bio-
chemistry in the University of Cambridge, and the fol-
lowing year he was appointed lecturer in pharmacology
at the University of Sheffield. In 1938 he became the
newly founded lecturer-in-charge of the department of
biochemistry. In 1939 he became an English citizen. By
1945 he was professor and director of the Medical
Research Council’s research unit established in the
department. In 1954 he was appointed Whitley Profes-
sor of Biochemistry in the University of Oxford, and
the Medical Research Council’s Unit for Research in
Cell Metabolism was transferred to Oxford.
At the University of Freiburg (1932), he discovered
a series of chemical reactions (now known as the urea
cycle) by which ammonia is converted to urea in mam-
malian tissue. For his discoveries of chemical reactions
in living organisms now known as the citric acid or
KREBS CYCLE, he was awarded the 1953 Nobel Prize
for physiology or medicine. These reactions involve the156 Krebs, Sir Hans Adolf
Portrait of Sir Hans Krebs (1900–81), German-British biochemist
and Nobel laureate. Krebs trained, like his father, in medicine.
During 1932 he discovered the ornithine cycle, in which the liver
converts amino acids to nitrogen and urea. The following year he
fled from Nazism to Britain. He eventually settled in Sheffield, and
it was there that he discovered the Krebs cycle. This describes
how the body breaks down glucose into carbon dioxide, water,
and energy. This is central to energy production in the mitochon-
dria of most cells and generates energy for whole organisms.
For this work he shared the 1953 Nobel Prize with F. Lipmann.
(Courtesy of Science Photo Library)