2. Predict the effect of fasting/starvation on the regulation of both glycolysis
ID: 195035 • Letter: 2
Question
2. Predict the effect of fasting/starvation on the regulation of both glycolysis and gluconcogenesis. How do you think glycolysis and gluconeogenesis would be regulated while fasting/starving? Which enzyme(s) do you think would be targeted? Why and how? (4 pts) 3. Pyruvate carboxylase (PC) uses biotin (vitamin B) as a cofactor to covert pyruvate to oxaloacetate () What amino acid of the enzyme is biotin covalently attached to? What kind of bond or functional group links biotin to this residue? Draw the structure of biotin attached to this amino acid of the enzyme, indicating stereochemistry ifDwhere applicable. What is the role of biotin in the reaction? (4 pts) (b) ATP hydrolysis is often used in reactions where an input of energy is required. Why does PC activity require ATP hydrolysis? Briefly describe why an input of energy needed in the PC reaction? (2 pts)Explanation / Answer
2. Effect of fasting/starvation on the regulation of glycolysis and gluconeogenesis:
Glycolysis is controlled by the amount of glucose present in the liver whereas gluconeogenesis is controlled by the amount of lactate present.
During starved conditions, gluconeogenesis predominates whereas glycolysis is diminished. Glucagon rises during starvation and leads to the increase in expression levels of enzymes namely fructose 1,6 bisphosphate and phosphoenolpyruvate carboxylase. These are the two key gluconeogenic enzymes and hence gluconeogenesis predominates.
On the other hand, starvation leads to the inhibition of pyruvate kinase which makes fructose 2, 6 bisphosphate. So, the levels of fructose 2,6 bisphosphate turns low during starvation and in turn regulates the secretion and activation of gluconeogenetic enzymes. Glucose produced during this time is essential for brain and liver.
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