Final answer:
The most likely effect of a covalent interaction between caffeine and adenosine receptors on the human body would be prolonged stimulation of the central nervous system, as this strong bond would lead to caffeine maintaining its antagonistic role over adenosine receptors for an extended period, causing prolonged alertness and delayed fatigue.
Step-by-step explanation:
If the interaction between caffeine and adenosine receptors were covalent, this would likely lead to prolonged stimulation of the central nervous system. Caffeine normally acts as a competitive antagonist of adenosine receptors; it reversibly binds these receptors without activating them, thus blocking the action of adenosine. Adenosine generally promotes sleep and suppresses arousal when bound to its receptors. By blocking adenosine, caffeine decreases sleepiness and increases alertness.
If this interaction were covalent (which implies a stronger, more stable chemical bond), caffeine would likely remain bound to the adenosine receptors for a much longer time, leading to extended effects like enhanced alertness and delayed fatigue. However, since covalent bonds are quite durable and not meant to break or reverse easily under normal physiological conditions, this could lead to a more constant state of stimulation and possibly exacerbate side effects such as insomnia and anxiety.