Lipid - Human Nutrition Science

Once inside the enterocyte, everything is recycled into the chylomicron, which goes to the lymph and into circulation via the portal vein. The chylomicron is a lipoprotein that is responsible for transporting dietary fats, such as triglycerides, from the intestines to various tissues in the body. It is formed in the enterocytes of the small intestine and then released into the lymphatic system. From there, it enters the bloodstream via the portal vein, where it can deliver the dietary fats to cells throughout the body.

Lingual lipase is the enzyme that begins limited fat digestion in the mouth and stomach. It is secreted by the lingual glands in the tongue and is responsible for breaking down triglycerides into diglycerides and fatty acids. This enzyme plays a crucial role in the initial stages of fat digestion, particularly in infants who have a higher amount of lingual lipase in their stomachs.

CCK, or cholecystokinin, is the hormone responsible for releasing bile from the gallbladder. Bile helps in the emulsification of fat, breaking it down into smaller droplets, which allows pancreatic enzymes to have better access to the fat molecules for digestion. GIP and secretin are not directly involved in the release of bile or the emulsification of fat.

Lipoprotein lipase is responsible for cleaving endogenous fatty acids from chylomicrons. Chylomicrons are large lipoprotein particles that transport dietary triglycerides from the intestines to various tissues in the body. Lipoprotein lipase is located on the surface of blood vessel walls and acts on chylomicrons, breaking down triglycerides into free fatty acids and glycerol. These free fatty acids can then be taken up by cells and used for energy or storage. Therefore, lipoprotein lipase plays a crucial role in the metabolism of dietary fats.

In the intestinal lumen, micelles are formed. Micelles are tiny structures composed of bile salts and other substances that help in the absorption of fats and fat-soluble vitamins. These micelles facilitate the diffusion of lipids into the intestinal lumen, where they can be absorbed by the intestinal cells. Additionally, the bile salts present in the micelles are recycled by being reabsorbed in the ileum and returned to the liver for reuse. This process ensures efficient digestion and absorption of fats in the intestine.

Hepatic lipase is the correct answer because it is the enzyme responsible for hydrolyzing endogenous triglyceride. This enzyme is primarily found in the liver and is involved in the breakdown of triglycerides into free fatty acids and glycerol, which can then be used for energy or stored in adipose tissue. Lipoprotein lipase, on the other hand, is responsible for hydrolyzing triglycerides in circulating lipoproteins, while cholesterol esterase is involved in the hydrolysis of cholesterol esters.

When a chylomicron is cleaved, it forms a chylomicron remnant. This remnant contains apoE, which is a protein that can bind to the LDL receptor. The binding of apoE to the LDL receptor allows the chylomicron remnant to be taken up and cleared from the bloodstream. Therefore, the correct answer is chylomicron remnant and apoE.