2. Predict the effect of fasting/starvation on the regulation of both glycolysis

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

In the fasted state, the liver secretes glucose through both breakdown of glycogen (glycogenolysis) and de novo glucose synthesis (gluconeogenesis). During pronged fasting, hepatic gluconeogenesis is the primary source of endogenous glucose production. Fasting also promotes lipolysis in adipose tissue to release nonesterified fatty acids which are converted into ketone bodies in the liver though mitochondrial oxidation and ketogenesis. Ketone bodies provide a metabolic fuel for extrahepatic tissues. Liver metabolic processes are tightly regulated by neuronal and hormonal systems.

Muscle breaks down glycogen and proteins and releases lactate and alanine. Alanine, lactate, and glycerol are delivered to the liver and used as precursors to synthesize glucose

Controlled by a single enzyme called bifunctional 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase

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