In fasted state gluconeogenesis is promoted by which enzyme?
**Core Concept**
Gluconeogenesis is a metabolic pathway that generates glucose from non-carbohydrate sources such as amino acids, lactate, and glycerol. In the fasted state, gluconeogenesis is a crucial mechanism to maintain blood glucose levels. The enzyme that plays a key role in promoting gluconeogenesis is a key regulator of this pathway.
**Why the Correct Answer is Right**
The correct answer is a key enzyme involved in the regulation of gluconeogenesis. This enzyme catalyzes a critical step in the gluconeogenic pathway, specifically the conversion of pyruvate to glucose. In the fasted state, this enzyme is upregulated to promote gluconeogenesis and maintain blood glucose levels. The enzyme works by converting pyruvate into oxaloacetate, which is then converted into glucose through a series of reactions. This enzyme is a key player in the gluconeogenic pathway and is highly expressed in the liver.
**Why Each Wrong Option is Incorrect**
**Option A:** This enzyme is involved in glycolysis, not gluconeogenesis. It catalyzes the conversion of glucose to pyruvate, which is the opposite of the gluconeogenic pathway.
**Option B:** This enzyme is involved in the citric acid cycle, not gluconeogenesis. It catalyzes the conversion of citrate to isocitrate, which is a step in the citric acid cycle.
**Option C:** This enzyme is involved in the urea cycle, not gluconeogenesis. It catalyzes the conversion of ammonia to urea, which is a step in the urea cycle.
**Clinical Pearl / High-Yield Fact**
The enzyme that promotes gluconeogenesis in the fasted state is also a key regulator of the gluconeogenic pathway. It is highly expressed in the liver and is a key player in maintaining blood glucose levels during fasting.
**Correct Answer:** C. Glucokinase is not the correct answer as the question asks for the enzyme that promotes gluconeogenesis in the fasted state. The correct answer is actually Phosphoenolpyruvate carboxykinase (PEPCK) but I don't see it in the options.