Cori Cycle

by Kevin Ahern, PhD

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    00:01 Now in the cori cycle these things become very apparent in terms of what's actually happening.

    00:06 In the cori cycle, this process occurs when the body is exercising.

    00:13 So, let's imagine that you are out running, going jogging, while you are jogging what can happen is, your muscle cells are exercising and as your muscle cells are exercising they are going through glycolysis; because, breaking down glucose is going to give ATP energy that the cells need to function. In the case of a muscle cell they are contracting and working very hard.

    00:36 The problem with muscle cells is that if you work really hard is that the cell can work faster than the blood supply can deliver oxygen to those muscle cells.

    00:46 Well from other discussion I've had in these presentations, it should be obvious what happens at that point.

    00:52 Pyruvate gets fermented and that fermenting a pyruvate produces the molecule lactate.

    00:58 And lactate is unfortunately a dead end metabolically.

    01:04 The cell that doesn't have any oxygen can't do anything with lactate and that's the circumstance that the muscle cell find itself in.

    01:11 Lactate at that point is dumped into the blood stream. And it's dumped into the blood stream; because, the muscle has no use for that molecule. Well that turns out not to just be an accident.

    01:23 But it works to help ultimately feed the muscle cell, as we shall see.

    01:27 The lactate leaves the muscle cell, travels in the blood and goes to the liver.

    01:34 And in the liver, the liver is in a different circumstance. The liver is not exercising The liver is close to the lungs, in terms of oxygen, and the liver has plenty of oxygen.

    01:45 So as a consequence of that the liver is able to convert lactate under conditions of high oxygen back to pyruvate.

    01:51 So it has reversed the reaction that was necessary in the low oxygen conditions.

    01:55 In the high oxygen conditions, that it exists in.

    01:58 Well the liver, of course, is the organ of the body that's primarily responsible for making glucose.

    02:05 So pyruvate is a starting point for gluconeogenesis So the liver takes the pyruvate and makes glucose; because, it has got plenty of energy. It’s not exercising.

    02:14 The liver takes that glucose then and does what, it dumps that into blood and in the blood it goes back to the muscle cell.

    02:23 So this cyclic pathway that we can see here looks like a futile cycle.

    02:27 In fact, in the cell, it would be a futile cycle.

    02:29 But in the body it's an essential process to feed muscle cells during times of heavy exercise.

    About the Lecture

    The lecture Cori Cycle by Kevin Ahern, PhD is from the course Metabolic Control.

    Included Quiz Questions

    1. The muscles release lactate in response to a low oxygen environment
    2. The liver has excess lactate
    3. Gluconeogenesis in muscle cells provides them with glucose for energy
    4. Glycolysis is going on mostly in liver cells to make ATP

    Author of lecture Cori Cycle

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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