Final answer:
Muscle contraction is paid for by metabolic pathways including glycolysis, β-oxidation of fats, the electron transport system, and the citric acid cycle, which all work together to supply the necessary ATP.
Step-by-step explanation:
The metabolic pathways utilized by muscle to 'pay' for their contraction are glycolysis, β-oxidation of fats, electron transport system, and the citric acid cycle. Initially, muscles rely on stored glycogen, which is broken down to produce glucose. This glucose then undergoes glycolysis to produce ATP for muscle contraction. When oxygen is available, pyruvate from glycolysis enters the mitochondria and participates in the citric acid cycle followed by the electron transport system, producing a significant amount of ATP. During intense exercises when oxygen supply is limited, the pathway may shift to lactic acid fermentation. Over time, as glycogen reserves decrease, fats are mobilized and metabolized through β-oxidation to provide fuel for aerobic respiration.