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Carbohydrate Metabolism: Gluconeogenesis

by Kevin Ahern, PhD
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    In a previous lecture I described the way in which glucose is broken down. But glucose is not the only sugar that we ourselves need to deal with. In this lecture I will talk about the metabolism of other sugars. I will discuss the process of gluconeogenesis, that's the way cells make glucose that they can use. And then last I will talk about the phenomenon of reciprocal regulation, the way cells control sugar metabolism. Now cells have a lot of different sugars that they get besides glucose. So it's important that we understand something about what they do. In this pathway we see that metabolism of a sugar known as galactose. Now we get galactose in our diet fairly regularly if we eat dairy products because galactose comes from lactose which is known as milk sugar. So our cells have to be able to metabolize galactose. To metabolize galactose, the metabolism is actually shown on the screen. I am gonna step you through it and it looks a little complicated but it is actually fairly simple. The reactions of galactose basically involve its conversion into an intermediate in glycolysis. Now this starts with an enzyme that has a mouthful of a name: galactose-1-phosphate uridyl transferase. Hopefully, the reaction is simpler then the name of the enzyme is. The reaction catalyzed by this enzyme takes galactose-1-phosphate on the upper left and combines it with UDP glucose on the lower left. And what it’s doing is essentially swapping the galactose for the glucose. So we see when this process happens that we start with galactose-1-phosphate and we end up with UDP galactose. UDP glucose releases a glucose-1-phosphate. So because of that we now have glucose-1-phosphate that is free. A glucose-1-phosphate is relatively easy to get into glycolysis because there is an...

    About the Lecture

    The lecture Carbohydrate Metabolism: Gluconeogenesis by Kevin Ahern, PhD is from the course Carbohydrate Metabolism. It contains the following chapters:

    • Metabolism of Galactose
    • Metabolism of Fructose
    • Gluconeogenesis - Synthesis of Glucose
    • Gluconeogenesis: Reactions
    • Regulation of Gluconeogenesis and Glycolysis

    Included Quiz Questions

    1. ...occurs ultimately in glycolysis.
    2. ...requires a CDP intermediate.
    3. ...requires lactase.
    4. ...produces fructose.
    1. It is inhibited by excess glucose.
    2. It bypasses regulatory enzymes in glycolysis.
    3. It ultimately produces glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.
    4. It can bypass phosphofructokinase (PFK).
    1. ...bypasses three enzyme reactions of glycolysis.
    2. ...starts with acetyl-CoA.
    3. ...occurs in most cells of the body.
    4. ...occurs solely in the cytoplasm and mitochondrion.
    1. ...catalyzes a reaction that requires biotin.
    2. ...catalyzes a reaction that uses GTP.
    3. ...catalyzes a reaction that produces phosphoenolpyruvate (PEP).
    4. ...catalyzes the backwards reaction of pyruvate kinase.
    1. It is found in the mitochondrion.
    2. It requires a triphosphate in the reaction it catalyzes.
    3. It has one four carbon substrate.
    4. It produces a glycolysis intermediate.
    1. ...releases phosphate in the reaction it catalyzes.
    2. ...requires ATP for catalysis.
    3. ...catalyzes an oxidation reaction.
    4. ...is regulated by phosphorylation.
    1. ...is important in the liver.
    2. ...uses a phosphate in the reaction it catalyzes.
    3. ...produces glucose from fructose-6-phosphate directly.
    4. ...is found in the mitochondrion.
    1. ...use energy and produce no net amounts of molecules.
    2. ...are favored when cells are running low on energy.
    3. ...are essential for catabolic processes.
    4. ...produce excess NAD+.

    Author of lecture Carbohydrate Metabolism: Gluconeogenesis

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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