Within the RBC, hypoxia stimulates glycolysis by which of the following regulating pathways?
**Core Concept**
Glycolysis is a metabolic pathway that converts glucose into pyruvate, producing energy for the red blood cell (RBC). Under conditions of hypoxia, the RBC's energy demand increases, and glycolysis is stimulated to meet this need. This process is crucial for maintaining the RBC's viability and function.
**Why the Correct Answer is Right**
Hypoxia stimulates glycolysis in RBCs through the activation of the **hexokinase** enzyme. Hexokinase catalyzes the first step of glycolysis, converting glucose into glucose-6-phosphate. **ADP-activated protein kinase (AMPK)** also plays a role in stimulating glycolysis by activating hexokinase and other enzymes involved in the glycolytic pathway. This adaptation allows the RBC to generate energy from glucose even in the absence of oxygen.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the regulation of glycolysis in RBCs under hypoxia.
* **Option B:** This option is incorrect because the regulation of glycolysis in RBCs is not primarily controlled by the phosphofructokinase enzyme.
* **Option D:** This option is incorrect because the regulation of glycolysis in RBCs is not primarily controlled by the pyruvate kinase enzyme.
**Clinical Pearl / High-Yield Fact**
The RBC's reliance on glycolysis for energy production is a critical adaptation that allows it to maintain its function in the absence of oxygen. This is particularly important in conditions such as anemia or carbon monoxide poisoning, where the RBC's energy demands are increased.
**Correct Answer: C. Hexokinase. Hexokinase activation by hypoxia stimulates glycolysis in RBCs.**