Transcript for:
Krebs Cycle Overview and Processes

Hello and welcome to Medsimplified. In this video, we will talk about the Krebs cycle. Krebs cycle is also known as the tricarboxylic acid cycle and it is a biochemical pathway that is used to generate energy through the oxidation of acetyl CoA.

It is also used for the synthesis of NADH and for the production of amino acids. Krebs cycle takes place in the mitochondria of the eukaryotes. and the cytosol of the prokaryotes.

The first step involved is actually a preparatory step which begins with pyruvate. Pyruvate is derived through the glycolysis of glucose which is a six carbon compound and it is split into two molecules of pyruvate which is a three carbon compound. The next step includes the oxidation of pyruvate into acetyl CoA. by the enzyme pyruvate dehydrogenase complex and in this reaction a molecule of carbon dioxide and a molecule of NADH is generated. The acetyl CoA is a two carbon compound.

In the next step the acetyl CoA combines with oxaloacetate which is a four carbon compound to form citrate and hence the resulting molecule is a six carbon compound. This reaction is catalyzed by the enzyme citrate synthase. In the next step, the citrate is isomerized into isocitrate by the enzyme aconitase. Next, the isocitrate is oxidized into alpha-ketoglutarate by the enzyme isocitrate dehydrogenase. And in this reaction, a molecule of NAD is reduced to NADH and a molecule of carbon dioxide is generated.

Hence, the alpha-ketoglutarate is a 5-carbon compound since one molecule of carbon is lost into carbon dioxide. Next, the alpha-ketoglutarate is converted into succinyl-CoA by the enzyme alpha-ketoglutarate dehydrogenase. And in this reaction also, a molecule of NAD is reduced to NADH and a molecule of carbon dioxide is released.

Hence, the succinyl-CoA is a 4-carbon compound. In the next step, the succinyl-CoA is converted into succinate by the enzyme succinyl-CoA synthase. In this reaction, a molecule of GTP is generated.

Next, succinate is converted into fumarate by the enzyme succinate dehydrogenase. In this reaction, a molecule of QH2 is generated which is used for the production of FADH2. Fumerate is then converted into malate by the enzyme fumarase. And in the last step, the malate is converted into oxaloacetate by the enzyme malate dehydrogenase.

And in this reaction also, NAD is reduced to NADH. Now let's look at the results of the Krebs cycle. Through each cycle of the Krebs cycle, following products are generated.

Three molecules of NADH, one molecule of FADH2, one molecule of GTP and two molecules of carbon dioxide. Now since glucose is split into two pyruvate compounds, For each molecule of glucose, this cycle runs twice. Hence, the products formed are 6 NADH, 2 FADH2, 2 GTP and 4 carbon dioxide.

All the NADH and FADH are next fed to the electron transport chain for the generation of ATP. So, this was a short description of the Krebs cycle. Thank you so much for watching this video.

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