Which substrates feed the Glycolytic Pathway?

• A. Fatty acids
• B. Glucose from bloodstream, muscle glycogen, or glycerol derived from fat
• C. Phosphocreatine
• D. Adenosine

Answer: (B)

Glycolysis is fueled by glucose entering the pathway from readily available sources: circulating glucose in the blood, glucose derived from muscle glycogen, and glycerol released from fat after it’s converted into intermediates that feed glycolysis. This is why the substrates listed in that option capture everything glycolysis can directly use as fuel. Fatty acids, while useful for energy through beta-oxidation and the TCA cycle, don’t feed glycolysis directly. Phosphocreatine provides a rapid ATP buffer rather than a glycolytic substrate, and adenosine is a nucleoside not used as a substrate in glycolysis.