Sandbox Oldenburg02 - Revision history

Verena Pietzner at 06:57, 28 July 2014

Verena Pietzner — Mon, 28 Jul 2014 06:57:20 GMT

←Older revision		Revision as of 06:57, 28 July 2014
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	combustion processes, Alber Szent-Györgyi was awarded the 1937 Nobel Prize in Physiology.</p>		combustion processes, Alber Szent-Györgyi was awarded the 1937 Nobel Prize in Physiology.</p>

-	<p>At the same time and independent from Szent-Györgyi, Franz Knoop and Carl Martius presendet the following reaction sequence in 1937. They also discovered that the decomposition of citric acid is done by an enzyme. ~~</p>~~</p>	+	<p>At the same time and independent from Szent-Györgyi, Franz Knoop and Carl Martius presendet the following reaction sequence in 1937. They also discovered that the decomposition of citric acid is done by an enzyme. </p>
	[[Image:discovery_4.jpg]]		[[Image:discovery_4.jpg]]
	<p>Figure 2: Reaction sequence of Knoop and Martius</p>		<p>Figure 2: Reaction sequence of Knoop and Martius</p>

Verena Pietzner at 06:56, 28 July 2014

Verena Pietzner — Mon, 28 Jul 2014 06:56:57 GMT

←Older revision		Revision as of 06:56, 28 July 2014
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	that succinate was still present in the tissue. Therefore he suggested that succinate served as a catalyst. From his experiments, he derived the following reaction sequence:</p>		that succinate was still present in the tissue. Therefore he suggested that succinate served as a catalyst. From his experiments, he derived the following reaction sequence:</p>

-	[[Image:discovery_2.~~gif~~]]	+	[[Image:discovery_2.jpg]]
	<p>Figure 1: Reaction sequence of Szent-Györgyi (1935)</p>		<p>Figure 1: Reaction sequence of Szent-Györgyi (1935)</p>
	<p>For his work in the field of cellular respiration and the catalytic role of fumarate in biological		<p>For his work in the field of cellular respiration and the catalytic role of fumarate in biological
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	converted into succinate. With this knowledge, Krebs could complete the reaction sequence of the cycle:</p>		converted into succinate. With this knowledge, Krebs could complete the reaction sequence of the cycle:</p>

-	<p>Citrate → Aconitate → Isocitrate → Ketoglutarate → Succinate → Fumarate → Malate → Oxalacetate</o:p~~></p>~~	+	<p>Citrate → Aconitate → Isocitrate → Ketoglutarate → Succinate → Fumarate → Malate → Oxalacetate</p>
-	~~</span~~>	+

	<p>The only two pieces that was now missing in the puzzle was the reaction that it returns to the beginning of the reaction		<p>The only two pieces that was now missing in the puzzle was the reaction that it returns to the beginning of the reaction

Verena Pietzner at 06:56, 28 July 2014

Verena Pietzner — Mon, 28 Jul 2014 06:56:26 GMT

←Older revision		Revision as of 06:56, 28 July 2014
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	that succinate was still present in the tissue. Therefore he suggested that succinate served as a catalyst. From his experiments, he derived the following reaction sequence:</p>		that succinate was still present in the tissue. Therefore he suggested that succinate served as a catalyst. From his experiments, he derived the following reaction sequence:</p>

-		+	[[Image:discovery_2.gif]]
-	~~<p><img src="entdeckung_image002~~.gif~~" width="448" height="149"></p>~~	+
	<p>Figure 1: Reaction sequence of Szent-Györgyi (1935)</p>		<p>Figure 1: Reaction sequence of Szent-Györgyi (1935)</p>
	<p>For his work in the field of cellular respiration and the catalytic role of fumarate in biological		<p>For his work in the field of cellular respiration and the catalytic role of fumarate in biological
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	<p>At the same time and independent from Szent-Györgyi, Franz Knoop and Carl Martius presendet the following reaction sequence in 1937. They also discovered that the decomposition of citric acid is done by an enzyme. </p></p>		<p>At the same time and independent from Szent-Györgyi, Franz Knoop and Carl Martius presendet the following reaction sequence in 1937. They also discovered that the decomposition of citric acid is done by an enzyme. </p></p>
-	~~<img src="entdeckung_image004.gif" alt="Knoop" width="586" height="182">~~	+	[[Image:discovery_4.jpg]]
-	<![~~endif]></span><span~~	+
-	~~style='mso-ansi-language~~:~~DE'>~~	+
-		+
	<p>Figure 2: Reaction sequence of Knoop and Martius</p>		<p>Figure 2: Reaction sequence of Knoop and Martius</p>

Verena Pietzner: New page:

The discovery of the Krebs cycle

The degradation pathway of glucose to pyruvate or lactate is known in his roughly sequence since the 1930s. However, the fact that six molecu...

Verena Pietzner — Mon, 28 Jul 2014 06:53:59 GMT

New page: <h2>The discovery of the Krebs cycle</h2> The degradation pathway of glucose to pyruvate or lactate is known in his roughly sequence since the 1930s. However, the fact that six molecu...

New page

<h2>The discovery of the Krebs cycle</h2>

The degradation pathway of glucose to pyruvate or lactate is known in his roughly sequence since the
1930s. However, the fact that six molecules of carbon dioxide and six molecules of water from can be obtained out of one molecule
of glucose, was not known at that time. Although some researchers indicated the presence of
dicarboxylic acids, but the structure of these compounds cold not be correlated with the structure of glucose.
In 1935, Albert Szent-Györgyi did some experiments with freshly prepared breast muscles. He discovered that the oxygen
consumption increased as soon as succinate, fumarate, malate or oxaloacetate have been added. However, the comsumption of oxygen was much higher than usual. In addition, Szent Györgyi found
that succinate was still present in the tissue. Therefore he suggested that succinate served as a catalyst. From his experiments, he derived the following reaction sequence:

<img src="entdeckung_image002.gif" width="448" height="149">
Figure 1: Reaction sequence of Szent-Györgyi (1935)
For his work in the field of cellular respiration and the catalytic role of fumarate in biological
combustion processes, Alber Szent-Györgyi was awarded the 1937 Nobel Prize in Physiology.

At the same time and independent from Szent-Györgyi, Franz Knoop and Carl Martius presendet the following reaction sequence in 1937. They also discovered that the decomposition of citric acid is done by an enzyme. 
<img src="entdeckung_image004.gif" alt="Knoop" width="586" height="182">
<![endif]>

Figure 2: Reaction sequence of Knoop and Martius

Hans Krebs could prove the reaction sequence of Knoop and Martius working with
freshly prepared pigeon breast muscle and additionally realised that the α-ketoglutarate was
converted into succinate. With this knowledge, Krebs could complete the reaction sequence of the cycle:

Citrate → Aconitate → Isocitrate → Ketoglutarate → Succinate → Fumarate → Malate → Oxalacetate</o:p>


The only two pieces that was now missing in the puzzle was the reaction that it returns to the beginning of the reaction
sequence: the reaction that leads from oxalacetate to citrate, and how this cycle relates to the glycolysis. The essential information for the discovery of the
citric acid cycle provided Martius and Knoop in 1937: Oxalacetate and pyruvate can be converted to citrate in the presence
of hydrogen peroxide. Pyruvate as a product of glucose metabolism was detected by Krebs as
the missing link. For he was familiar with the principle of a catalytic cyclic reaction sequence
(in 1932 he investigated the urea cycle together with Kurt Henseleit), Krebs transformed the linear reaction sequence to a cyclic system. In the same year he and WA Johnson could
suggest the citric acid cycle as an explanation for previously clarified observations. The fact that not pyruvate, but acetyl-CoA reacts with oxalacetate
into citrate, was discarded in 1951.

For the discovery of the citric acid cycle Hans Adolf Krebs awarded jointly with Fritz
Albert Lipmann the Nobel Prize in Physiology in 1953.