17. Gluconeogenesis. Substrates, importance. Overcoming the irreversible steps of glycolysis. Regulation. Tissue localization. Maintaining of the blood sugar level.

Describe the importance of gluconeogenesis for the human body. Which tissues critically depend on glucose as their energy source? What happens when glycogen stores are depleted?

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List the main substrates of gluconeogenesis and explain their origins. Why can’t acetyl-CoA be used for net glucose synthesis?

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Illustrate the three irreversible steps of glycolysis that must be bypassed in gluconeogenesis. Describe the enzymatic reactions that allow these obstacles to be overcome. What are the energetic differences between glycolytic and gluconeogenic reactions?

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Explain the role of transporting oxaloacetate from the mitochondrion to the cytosol in gluconeogenesis. Why is this step necessary? Which enzymes and transporters are involved?

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Describe in detail the regulatory mechanisms of gluconeogenesis. How do the hormones glucagon and insulin influence the activity of key gluconeogenic enzymes? What is the role of fructose 2,6-bisphosphate in the reciprocal regulation of glycolysis and gluconeogenesis?

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In which tissues does gluconeogenesis primarily occur? What is the relative contribution of the liver and kidneys to maintaining blood glucose levels? What is the potential role of the small intestine?

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Discuss the role of the Cori cycle and the alanine cycle in gluconeogenesis. How do these interorgan cycles contribute to recycling lactate and alanine produced by peripheral tissues?

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Analyze the clinical aspects related to defects in gluconeogenesis. What are the consequences of a deficiency in fructose-1,6-bisphosphatase? Why can ethanol induce hypoglycemia? What are the peculiarities of gluconeogenesis in newborns?

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