Reactions above show the conversion of pyruvate to PEP. This is a key regulatory
ID: 84070 • Letter: R
Question
Reactions above show the conversion of pyruvate to PEP. This is a key regulatory point in which cycle? _______________
This process requires:
1)pyruvate carboxylase to convert pyruvate to __________ and PEP carboxykinase (PEPCK) to convert oxaloacetate to ___________. Would glucose level increase/decrease (circle one) if an inhibitor of pyruvate carboxylase was present? What about levels of citrate? Increase/decrease/no effect? (circle one)
PO2 pyruvate O o O O O O PEPCK carboxylase CH3-C C-C-O C-O O-C CH2-C C-O CH2 GTP GDP Phospho enol- CO2 pyruvate (PEP) Oxaloacetate Pyruvate HCO3 ATP ADP PiExplanation / Answer
In the process of respiration, the second stage is called the TCA cycle or Krebs cycle where the glucose broken down into pyruvate is further released out as carbon dioxide molecules while in the process also producing the ATP. There are a series of steps in the TCA cycle.This cycle has many intermediates such as oxaloacetate, citrate, fumarate, malate etc.., Apart from the TCA cycle, these molecules are also used in the other metabolic pathways. Hence these intermediates are often pulled out and also replenished through the process called anaplerotic pathways. In the TCA, Pyruvate is usually converted into acetyl CoA molecule.then it is further converted into citrate by combining with oxaloacetate.The anaplerotic pathway here is pyruvate is directly converted to oxaloacetate by the enzyme pyruvate carboxylase. Oxaloacetate is a gluconeogenic compound which means it acts as a precursor for the production of glucose and the levels of glucose would decrease if there was a pyruvate carboxylase inhibitor as this prevents the conversion of oxaloacetate to glucose.Of course PEPCK an enzyme which converts the oxaloacetate to phosphoenolpyruvate is necessary. For the formation of citrate both oxaloacetate and acetylCoA are required.If the pyruvate is directly converted to oxaloacetate the supply of acetyl CoA would stop which would result in the reduced formation of citrate.If instead there was an inhibitor of pyruvate carboxylase the TCA cycle would proceed further as both the acetyl CoA and oxaloacetate from the conversion of malate are used to form citrate.
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