To where do amino acids not being used by intestinal cells typically go?

Amino acids that are not utilized by intestinal cells primarily enter the hepatic portal circulation and are transported to the liver. The liver plays a crucial role in processing these amino acids for various functions, including protein synthesis, conversion to energy, or conversion into other compounds based on the body's needs.

Once in the liver, amino acids can be used to synthesize proteins that the body requires, including enzymes, hormones, and structural proteins. Additionally, the liver can convert excess amino acids into glucose through gluconeogenesis or into fatty acids for energy storage. Thus, the liver serves as a central hub for amino acid metabolism, making it the primary destination for amino acids after they pass through the intestines.

The other options do not serve this primary function. For instance, the spleen is involved in immune responses and the filtering of blood but does not directly process amino acids. The heart is primarily focused on pumping blood and does not play a direct role in amino acid metabolism. The mention of "pancake" is irrelevant and does not pertain to biological processes.