what enzymes does gluconeogenesis use to bypass the irreversible reactions of glycolysis
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Which enzyme(south) featherbed the pyruvate kinase reaction of glycolysis in gluconeogenesis?
Possible Answers:
pyruvate carboxylase only
phosphoglycerate mutase and pyruvate carboxylase
fructose bis-phosphatase only
phosphoenolpyruvate carboxykinase (PEPCK) merely
pyruvate carboxylase and phosphoenolpyruvate carboxykinase (PEPCK)
Correct answer:
pyruvate carboxylase and phosphoenolpyruvate carboxykinase (PEPCK)
Explanation:
In the first step of gluconeogenesis, pyruvate carboxylase (with ATP and bicarbonate) converts pyruvate to oxaloacetate. Then phosphoenolpyruvate carboxykinase (PEPCK) (with GTP) releases carbon dioxide to give phosphoenolpyruvate.
Which one of the post-obit statements about PEP (phosphoenolpyruvate) synthesis is correct?
Possible Answers:
Pyruvate is converted to PEP by the citric acid cycle.
Pyruvate tin be converted to PEP past a mutase.
Pyruvate can be converted to PEP by a combination of reactions that use energy from 2 dissimilar types of nucleotide triphosphate.
Pyruvate tin be converted to PEP by pyruvate kinase.
Correct respond:
Pyruvate tin be converted to PEP by a combination of reactions that utilise energy from two unlike types of nucleotide triphosphate.
Explanation:
GTP and ATP are used to drive the reactions that brand pyruvate into PEP. Specifically, ATP catalyzes PEP carboxylase and GTP catalyzes PEP carboxykinase. A mutase moves phosphate groups already on a molecule, so information technology cannot be used to introduce one. The citric acrid wheel can make pyruvate into any of the citric acid intermediates, merely PEP isn't ane of them. Pyruvate kinase is the enzyme that makes pyruvate into PEP, which is but favorable in the forward direction.
In order for gluconeogenesis to generate 1 molecule of glucose, how many molecules of ATP and/or GTP are needed?
Right answer:
Explanation:
Answering this question requires knowledge of the pathway of gluconeogenesis. In this pathway, non-saccharide carbon substrates such as lactate, pyruvate, and certain amino acids are used to generate glucose as the concluding product. Much of this pathway utilizes the aforementioned enzymes used in glycolysis, which is substantially the contrary of gluconeogenesis. Yet, it is critical to note that there are iii reactions in glycolysis that are irreversible. Therefore, gluconeogenesis is not an verbal reverse of glycolysis, and instead in that location are a few different enzymes in gluconeogenesis that bypass these irreversible reactions. One of the irreversible steps in glycolysis is the formation of pyruvate from phosphoenolpyruvate (PEP), catalyzed by the glycolytic enzyme pyruvate kinase. To bypass this irreversible reaction, gluconeogenesis makes use of 2 enzymes. First, the enzyme pyruvate carboxylase converts pyruvate into oxaloacetate, which requires the input of i molecule of ATP per molecule of pyruvate used. Next, the gluconeogenic enzyme PEP carboxykinase converts oxaloacetate into PEP, using one molecule of GTP per molecule of oxaloacetate used. The other step that requires an investment of energy is by a reaction that is reversible. The conversion of three-phosphoglycerate into 1,iii-bisphosphoglycerate (1,3-BPG) by the enzyme phosphoglycerate kinase utilizes i molecule of ATP per molecule of 1,3-BPG generated. This is a reversible reaction. Now, we can add up the energy requirements. Since each of these reactions need to occur twice in order to generate a single molecule of glucose, nosotros'll need to multiply the free energy investment by ii in each step. Thus, we take two molecules of ATP from the reaction catalyzed by pyruvate carboxylase. We besides have two molecules of GTP from the reaction catalyzed by PEP carboxykinase. And lastly, we accept two molecules of ATP used from the reaction catalyzed past phosphoglycerate kinase. Adding all of these up, nosotros have a total of four molecules of ATP and ii molecules of GTP.
Which of the following are true about oxaloacetate?
Possible Answers:
It is a lipid
It is an intermediary in glycolysis
It is an intermediary in the synthesis of glucose from glycerol
It can cross mitochondrial membranes
It is an intermediary in the synthesis of glucose from lactate
Right answer:
It is an intermediary in the synthesis of glucose from lactate
Explanation:
Oxaloacetate contributes to fat acrid synthesis, but it'south non a lipid, because, amidst other reasons, it's not hydrophobic. This is also why it cannot cantankerous mitochondrial membranes. Glucose can exist synthesized from glycerol, just this process occurs via dihydroxyacetone phosphate, and doesn't involve oxaloacetate. Oxaloacetate is synthesized from pyruvate, which is the terminate product of glycolysis, so oxaloacetate cannot be an intermediary in glycolysis. Nevertheless, lactate tin can exist converted to pyruvate, which is the principle substrate for gluconeogenesis (sometimes chosen "reverse glycolysis"). In gluconeogenesis, oxaloacetate is an intermediary in the conversion of pyruvate to phosphoenolpyruvate, and so that makes it an intermediary, as well, in the synthesis of glucose from lactate.
Which of the following is an example of futile cycling?
Possible Answers:
Glycolysis and beta oxidation occurring simultaneously.
Glycolysis and oxidative phosphorylation occurring simultaneously.
Glycolysis and ketogenesis occurring simultaneously.
Glycolysis and the Krebs cycle occurring simultaneously.
Glycolysis and gluconeogenesis occurring simultaneously.
Correct answer:
Glycolysis and gluconeogenesis occurring simultaneously.
Explanation:
Futile cycling occurs when two metabolic processes occur in opposite directions, and thus outcome in no cyberspace change. This is very wasteful, and not platonic. The only instance of the reply choices of metabolic processes occurring in opposite directions is glycolysis and gluconeogenesis occurring simultaneously. Other possible examples could include: glycogenesis and glycogenolysis, beta-oxidation and fatty acid synthesis, etc.
Which of the following is non true nearly the gluconeogenesis pathway'south role in organismal homeostasis?
Possible Answers:
Gluconeogenesis is a pathway for cells to create glucose from various precursors when glucose itself is unavailable
Gluconeogenesis will typically remain quiescent if the prison cell has an overabundance of energy from other pathways
Gluconeogenesis is primarily restricted to the liver and kidneys in mammalian species
Pyruvate and glycerol tin can be substrates for conversion to glucose in gluconeogenesis
Gluconeogenesis occurs when an organism consumes abnormally high amounts of carbohydrates and fat acids
Right answer:
Gluconeogenesis occurs when an organism consumes abnormally high amounts of carbohydrates and fatty acids
Caption:
Gluconeogenesis occurs in times of starvation, fasting, and depression access to sources of glucose. This is the cells way of creating its own precursor when none is available, albeit at a high energetic cost (one cycle of gluconeogenesis can toll 6 ATP). Thus, it is untrue that gluconeogenesis occurs during loftier consumption of carbohydrates and fatty acids. Each other option is truthful regarding gluconeogenesis.
During anaerobic conditions, lactate travels from the muscle to the liver via the bloodstream.
What is lactic acrid converted into when it reaches the liver earlier information technology returns back to the muscle?
Possible Answers:
Glycogen
Citrate
Glucose
Acetyl-CoA
Glucagon
Caption:
The Cori cycle comes into play during anaerobic atmospheric condition; where lactate from glycolysis travels from the muscle to the liver to exist converted into glucose via gluconeogenesis. The glucose is then sent dorsum to the musculus to be used for energy. Note that some of the lactate that is converted into glucose tin can be stored every bit glycogen in the liver, but glycogen is not transported from the liver to the skeletal musculus.
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