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Process of Metabolism

by Georgina Cornwall, PhD
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    00:00 In this figure you can see some negative feedback loops. So the whole thing, you'll recall negative feedback works by the end product feeding back somewhere higher in the chain.

    21:22 Cellular metabolism or cellular respiration is a great example of how this happens.

    00:17 For example, lets start just with ATP. If we have tons of ATP, we really don't need to break down more sugar and produce anymore ATP. So, ATP levels are high, they are going to bind on to phosphofructokinase, one of the enzyme in the process of glycolysis. And they will shut down the action of phosphofructokinase.

    00:43 I believe it's an allosteric inhibitor. And that will shut the process down, whereas if we have lots of ADP, we may see that ADP allosterically activates phosphofructokinase to allow it to take glucose and produce more pyruvate and thus more ATP.

    01:06 So, those two end products feedback in a negative feedback loop in order to regulate the production of themselves. Another couple of key pieces that act in the regulation of these cycles would be NADH.

    01:22 NADH, the electron electron carriers, when there is tons of electron carriers, and they all have their electrons and protons, and they are off to the party at the electron transport chain, then they will feedback on pyruvate oxidation and prevent the production of more NADH's, cause we don't need them. Finally, we'll look at citrate. Citrate is one of the early intermediaries of the Krebs cycle.

    01:51 Citrate can also feedback if there are high levels citrate and act to negatively impact the production of more citrate. So, it's regulating the production of itself.

    02:05 Again, negative feedback is one of the primary mechanisms for controlling the rate of cellular respiration.

    02:12 Regardless of which fuels we're using, we're going to see that end products feedback to the beginning to slow down the process. And if there's not enough of the end products, then that will activate the process.

    02:23 Bringing back together our conversation on enzymes, where we considered allosteric activation and allosteric inhibition, ADP and ATP play a primary role in regulating the enzyme phosphofructokinase.

    02:38 So now, you have a fairly good understanding of where all three fuel types enter into the process of cell respiration.

    02:48 We've learned that proteins and fats are broken down into their constituents, and they enter cell respiration at various points throughout the process. We also have found that Acetyl CoA is a pivotal molecule in metabolism.

    03:04 And we have learned that the products of cell respiration also can feedback in a negative feedback loop to regulate the whole process. So now, you should be able to identify some of the entry points for proteins and fats in the process of cellular respiration, as well as describe some of the intermediates.

    03:28 And finally you should be able to identify some of the key regulators in the process of cell respiration.

    03:36 Thanks so much for your attention. I look forward to seing you in the next lecture.


    About the Lecture

    The lecture Process of Metabolism by Georgina Cornwall, PhD is from the course Energy, Enzymes and Metabolism.


    Included Quiz Questions

    1. If ATP levels are high, it is important to directly inhibit the reaction that commits the substrate to glycolysis to allow the substrate to be available for other reactions, since the cell has ample energy.
    2. If ATP levels are high, this provides a mechanism to directly inhibit the Krebs cycle, thus preventing further generation of NADH, FADH2 and ATP molecules that are not needed.
    3. If ATP levels are high, it is important to inhibit ATP synthase, and phosphofructokinase directly inhibits ATP synthase.
    4. If ATP levels are high, this provides a mechanism to directly inhibit the electron transport chain, thus preventing the formation of a proton gradient in the intermembrane space of mitochondria.
    1. …negative feedback mechanism.
    2. …positive feedback mechanism.
    3. …substrate concentration.
    4. …the presence of O2.
    5. …the presence of CO2.

    Author of lecture Process of Metabolism

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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    Great!
    By B?o B. on 30. June 2018 for Process of Metabolism

    You make it much more easier. However, I still understand all important points. Thank you!

     
    The Very Best So Far!!!!
    By Angela N. on 20. March 2018 for Process of Metabolism

    I do not think there can be any simpler explanation of these concepts. Dr. Cornwall takes her time to explain these concepts in a way that they stick with you, and the analogies she uses engrave them into the medulla so that you can relate to the concept. You can't beat this! This is exceptional!!!! Thank you so much!!

     
    Exceptional lecturer.
    By Anthony F. on 13. July 2017 for Process of Metabolism

    What I loved the most about this lecture was how Dr. Cornwall actually took her time to explain the concepts discussed, and even used simple analogies to ensure that the information was easier to digest. This is something you find lacking in many professional lectures. Thanks again Dr. Cornwall!