Final answer:
FG fibers contain higher concentrations of glycogen and rely on anaerobic glycolysis for ATP production, resulting in rapid contractions but quicker fatigue compared to oxidative fibers.
Step-by-step explanation:
Molecules that are more likely to be found in higher concentrations in a fast glycolytic fiber include high amounts of glycogen. Fast glycolytic (FG) fibers primarily create ATP through anaerobic glycolysis, which is less efficient than oxidative pathways when it comes to the amount of ATP produced per metabolic cycle, leading to quicker fatigue. The FG fibers are characterized by having a large diameter, substantial glycogen reserves, and they lack significant amounts of mitochondria and myoglobin, giving them a white color. These fibers facilitate rapid, powerful movements but can sustain this activity only for short durations.