Hans Krebs

The held passages do not report his own experiments. They show the name in use: the cycle as a source of NADH and FADH2²³, a limit on pyruvate entry in astrocytes⁴, and a regulator in beta cells⁵.

Born: 25 August 1900
Died: 22 November 1981
Country: Germany
Field: biochemist, physician, university teacher
In the library: 0 works, named in 7 passages elsewhere
Facts from: Wikidata · Wikipedia

The cycle as described

Protasoni and Zeviani place the Krebs cycle in the mitochondrial matrix, downstream of glycolysis¹. Glucose becomes pyruvate, pyruvate becomes acetyl-CoA, and the cycle then runs. They count nine enzymatic reactions. Each round yields three NADH, one FADH2 and one GTP². They also trace FADH2 to the oxidation of succinate to fumarate at complex II. This feeds the ubiquinol pool but does not itself pump protons³.

Use in later bioenergetics

Later authors treat the cycle as a control point in cell physiology. Rose and colleagues report that pyruvate entry into the cycle is limited in astrocytes by reduced pyruvate dehydrogenase activity, which leaves a surplus of pyruvate⁴. Dolenšek and colleagues write that citrate, as a regulatory factor in glucose-induced insulin secretion, influences Krebs cycle activity in pancreatic beta cells⁵. In both cases the cycle's activity is linked to cell behaviour.

SourcesEach quotation was checked word for word against the passage it opens.

known as the citric acid cycle (or tricarboxylic acid cycle or Krebs cycle, Figure 4), which takes place in mitochondria and is aerobic.Protasoni M, Zeviani M, 2021 · Mitochondrial Structure and Bioenergetics in Normal and Disease Conditions · open at passage 27
This cycle is composed of nine different enzymatic reactions and each round generates three nicotinamide adenine dinucleotide (NADH) molecules, one flavine adenine dinucleotide (FADH2) and one guanosine triphosphate (GTP).Protasoni M, Zeviani M, 2021 · Mitochondrial Structure and Bioenergetics in Normal and Disease Conditions · open at passage 27
FADH2 derives from the oxidation of succinate to fumarate by complex II (CII, succinate dehydrogenase) during the Krebs cycleProtasoni M, Zeviani M, 2021 · Mitochondrial Structure and Bioenergetics in Normal and Disease Conditions · open at passage 45
Pyruvate entry into the tricarboxylic acid (TCA or Krebs) cycle (Figure 2.1) is limited by a reduced activity of pyruvate dehydrogenase (PDH) in astrocytesRose J, Brian C, Pappa A, Panayiotidis MI, Franco R, 2020 · Mitochondrial Metabolism in Astrocytes Regulates Brain Bioenergetics… · open at passage 9
in GIIS citrate is an important regulatory MCF and influences Krebs cycle activityDolenšek J, Špelič D, Klemen MS, Žalik B, Gosak M, Rupnik…, 2015 · Membrane Potential and Calcium Dynamics in Beta Cells from Mouse Pancreas… · open at passage 4