Metabolism | Transition Stage (Preparatory Phase)

I enjoy nerds in this video we're going to continue on and we're going to talk about the transition step or even sometimes they call the preparation phase so if you remember we left off with forming pyruvate from glycolysis right so from glycolysis we made pyruvate and pyruvate was a three carbon molecule right it was a three carbon molecule that we form from the end product of glycolysis and if you remember I said so again it's three carbons if you remember I told you that the only way that pyruvate can get taken into the mitochondria right is if there is oxygen because remember NADH that was generated within glycolysis has to go and drop those hydride ions onto the electron transport chain if not and there's no oxygen it drops those high drives off onto pyruvate and converts them into lactic acid and this pathway won't occur but if there is oxygen so again when is this part occurring this is occurring in the presence of oxygen in other words it has to be under aerobic conditions so the only way that pyruvate can get taken into the mitochondria and start getting converted to this next molecule is if there is oxygen present now when pyruvate is transported from the cytosol into the mitochondria there's a specific enzyme right here that's going to be controlling this we're going to talk about this in more detail in the biochemistry video but specifically look what happens here Piru baby's three carbons right look what happens at the end of this reaction it goes from three carbons to two carbons another thing happens let me show it like this look at this you see that right there I added something on to this two carbon molecule this two carbon molecule has this thing on it called a co enzyme a so what did I do I took pyruvate which is my 3 carbon molecule so this is my PI root of 8 and guess what I convert it into I convert it into a seagull Co a acetyl co a now acetyl co has two carbons pyruvate is 3 carbon so that means I had to lose a carbon I do and whenever you lose carbons you want to know what's called whenever there is a removal of a carbon they call that decarboxylation okay so decarboxylation is removing a carbon off of this substrate in the form of co2 so that's one part of this enzyme okay this is going to be working I'm going to mention the enzyme in a second another thing that the enzyme does is obviously it's adding on this coenzyme a it's adding on this co enzyme a this is getting added into this reaction you know what else is happening I'm taking NAD+ and I'm converting this into in ADH so this guy has must has a specific hydride ions that I'm going to rip off of him in order to convert him into acetyl co a and for him to be able to gain hydride ions so now here's another thing remember I told you that at the end of like hollis aside form pyruvate right but how many of the pyruvates - i'm actually making two of these pyruvate so I'm actually getting to pyruvate molecules so if I'm getting two of these pyruvate molecules how many co claims am I making - if I'm making two acetyl co a s how many co2 is am I actually generating I'm technically one from the first pyruvate and then another from the second pyruvate so that is a total of two co 2's how many Koei's am i adding into this process then I must be adding in two quois because I'm going to get two acetyl co a and how many nad positives are being converted into NADH as well if there's two pyruvates one for one pyruvate and then second for the other pyruvate so this is two of these this whole process is regulated by specific enzyme and this enzyme we'll talk about this in great detail biochemistry this enzyme is called a pyruvate dehydrogenase enzyme and this enzyme is super super interesting but he is the enzyme that is catalyzing this reaction here he is the one who is catalyzing this reaction now whenever this happens remember that this is a root this is an irreversible step in other words this step can't go backwards I can't go from acetyl coit to pyruvate so remember that pdh is not it going to be a reversible enzyme it's irreversible it only works in unidirectional not bidirectional only one direction so again as a result what did I get out of this transition state I went from I brought the pyruvate into the actual mitochondria and the presence of oxygen aerobic conditions in other words the NADH had to drop those hydrides onto the electron transport chain if that happens pyruvate gets brought into the mitochondria acted on by the pyruvate dehydrogenase and then what happens this enzyme will pull off two co2 molecules add in two Koei's generate two NADH s and form two acetyl co ways which will then go down into the Krebs cycle are in the next video we're going to go over the mechanism of this process in more detail and the regulation alright see you then

Channel: Ninja Nerd

Views: 149,215

Rating: 4.9834394 out of 5

Keywords: Transition stage, preparatory phase, metabolism

Id: 5WHFJ0ypeFE

Length: 6min 1sec (361 seconds)

Published: Tue Jun 13 2017