Which substrate can be metabolized anaerobically?

Glucose is the correct substrate that can be metabolized anaerobically because it undergoes glycolysis, a process that breaks down glucose to produce energy without the need for oxygen. During glycolysis, glucose is converted into pyruvate, and if oxygen is limited, pyruvate is further converted into lactate through lactic acid fermentation. This pathway allows for ATP production in environments where aerobic metabolism cannot occur, such as during intense exercise when oxygen supply is insufficient.

In contrast, fatty acids require oxygen for their beta-oxidation and subsequent metabolism in the mitochondria, thus they cannot be metabolized anaerobically. Amino acids can enter metabolic pathways, but their primary role is not as a quick energy source in anaerobic conditions; they are primarily utilized for protein synthesis and other functions. Lactate is a product of anaerobic metabolism of glucose, not a substrate that can be further metabolized anaerobically. Therefore, glucose stands out as the primary carbohydrate that can be effectively metabolized in the absence of oxygen.