Final answer:
Amino acids are absorbed into the bloodstream largely by secondary active transport with Na+, utilizing the sodium gradient managed by ATP-powered pumps.
Step-by-step explanation:
Free amino acids are absorbed into the bloodstream primarily through secondary active transport with Na+. This process involves the use of a cotransport mechanism, where the movement of sodium ions down their concentration gradient facilitates the uptake of amino acids against their gradient. This mechanism requires energy indirectly sourced from ATP that is used to maintain the sodium gradient through the action of the sodium-potassium pump. Amino acids are important nutrients, and their absorption in the small intestine is critical for the synthesis of proteins in our body.