Final answer:
Triglycerides are not absorbed into blood capillaries; instead, they are absorbed by enterocytes, reassembled, and enter lacteals of the lymphatic system as chylomicrons. Amino acids and monosaccharides are absorbed directly into the capillaries.
Step-by-step explanation:
The correct answer to the question about which of the following is not absorbed into capillaries is triglycerides. Unlike amino acids and monosaccharides, triglycerides are not directly absorbed into the blood capillaries. Before absorption, dietary fats, which include triglycerides, are emulsified into micelles with the help of bile salts and lecithin. These micelles allow fats to be transported to the enterocytes (intestinal cells), where fats are absorbed and reassembled into triglycerides. These reformed triglycerides are then packed with other lipids and proteins into structures called chylomicrons, which enter the lacteals of the lymphatic system rather than the blood capillaries. Amino acids and monosaccharides, on the other hand, are directly absorbed into the capillaries through different mechanisms including active transport and facilitated diffusion.