Not glucogenic is
**Core Concept**
Fructose is a simple sugar that can be converted into glucose through gluconeogenesis, a metabolic pathway that generates glucose from non-carbohydrate sources. However, certain compounds in the body cannot be converted into glucose through this pathway, and are therefore glucogenic or non-glucogenic.
**Why the Correct Answer is Right**
Fructose can be metabolized through the pentose phosphate pathway, which generates NADPH and ribose-5-phosphate, but it cannot be converted into glucose due to the lack of a glucose-6-phosphate dehydrogenase reaction. This is because fructose is primarily metabolized by the enzyme fructokinase, which phosphorylates fructose to form fructose-1-phosphate, which is then further metabolized to form glyceraldehyde and dihydroxyacetone phosphate. These intermediates can be converted into glycolytic intermediates, but not into glucose.
**Why Each Wrong Option is Incorrect**
* **Option A:** Glucose is glucogenic because it can be converted into glucose through gluconeogenesis.
* **Option B:** Glycogen is glucogenic because it can be broken down into glucose through glycogenolysis.
* **Option D:** Lactate is glucogenic because it can be converted into glucose through gluconeogenesis.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that fructose is not glucogenic, and its metabolism is primarily focused on generating energy through the pentose phosphate pathway.
**Correct Answer:** C. Fructose.