Can Ketone Bodies Be Converted To Glucose?

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Metabolism Flashcards | Quizlet

The three key enzymes catalyzing the three essentially irreversible reactions of glycolysis are, in order: a/ citrate synthase, hexokinase, pyruvate carboxylase b/ pyruvate kinase, phosphofructokinase, protein kinase A c/ protein kinase A (PKA), PFK, hexokinase b/ most of the time in most of the body's tissues c/ after meals in the liver and most of the time in most tissues d/ most of the time in the liver and during strenuous exercise in muscle tissue e/ after meals in the liver and most tissues When blood glucose is low, as during fasting or exercise, glycogen in muscle is broken down by the enzyme ___ to produce ___, which is converted to ___for glycolysis. a/ glucose synthase glucose 6-phosphate, glucose 1-phosphate b/ glycogen phosphorylase, glucose 6P, glucose 1P c/ glycogen phosphorylase, glucose 1P, PEP d/ glycogen carboxylase, glucose, glucose 6P e/ glycogen phosphorylase, glucose 1P, glucose 6P Aside from allosteric regulation by glucose 6-phosphate (glucose 6P), glycogen synthesis and breakdown in muscle is regulated by intracellular signaling pathways controlled by insulin, adrenalin and glucagon. Insulin ___ glucose uptake by tissues, to be stored as glycogen if there Continue reading >>

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  1. Doug Freyburger

    Others have mentioned the chemical details that lead to limits. That's only one side of the story. The other side is redundancy in energy production. Ketones can be used in anaerobic energy production. It's not as efficient but it is faster. There are times when fast beats efficient so redundancy gets selected for.

  2. Anand R

    Acetyl CoA can’t be circulated for two reasons: it’s a high energy compound and it’s labile. So it’s not a stable form for circulation to tissues. Also acetyl coA cannot cross cell membrane.
    Ketone bodies are an alternate fuel source. More importantly, they are water soluble analogs of fatty acids. This is important since, during starvation there is fat breakdown and excess fatty acids circulate in blood. However, fatty acids cannot be used by brain as fuel since, they cannot cross the blood brain barrier. Liver by producing ketone bodies helps brain cells during starvation.

    Also, these ketone bodies, as such, can be used by other tissues as well. There by other tissues refrain from using glucose. Hence, ketone bodies have a glucose-sparing effect. This glucose will be available for tissues like brain and red cells for use.

  3. Barry Gehm

    It’s because oxaloacetate is needed to metabolize acetyl-CoA (first step in the Krebs cycle is the reaction of acetyl-CoA with oxaloacetate) and is also needed (and used up) in gluconeogenesis (the production of glucose from amino acids and other small molecules, but NOT from acetyl groups or fatty acids). The liver is primarily responsible for gluconeogenesis, and if it uses up oxaloacetate on that, acetyl-CoA builds up and ties up all the coenzyme A in acetylated form. In order to alleviate this, the liver converts the acetyl-CoA into ketone bodies, and releases them into the blood. These, as the book says, are taken up by other tissues (such as brain and muscle) and converted back into acetyl-CoA. A key point is that these cells can use the acetyl-CoA because they are not depleted in oxaloacetate because they do not carry out gluconeogenesis.

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