Triglycerides in the context of Low-density lipoprotein

Animal fats are lipids derived from animals which are used by the animal for a multitude of functions, or can be used by humans for dietary, sanitary, and cosmetic purposes. Depending on the temperature of the fat, it can change between a solid state and a liquid (oil) state. Chemically, both fats and oils are composed of triglycerides. Although many animal parts and secretions may yield oil, in commercial practice, oil is extracted primarily from rendered tissue fats from livestock animals like pigs, chickens and cows. Dairy products yield animal fat and oil products such as butter.

In biochemistry, an ether lipid refers to any lipid in which the lipid "tail" group is attached to the glycerol backbone via an ether bond at any position. In contrast, conventional glycerophospholipids and triglycerides are triesters. Structural types include:

• Ether phospholipids: phospholipids are known to have ether-linked "tails" instead of the usual ester linkage.
  • Ether on sn-1, ester on sn-2: "ether lipids" in the context of bacteria and eukaryotes refer to this class of lipids. Compared to the usual 1,2-diacyl-sn-glycerol (DAG), the sn-1 linkage is replaced with an ester bond.

Based on whether the sn-1 lipid is unsaturated next to the ether linkage, they can be further divided into alkenyl-acylphospholipids ("plasmenylphospholipid", 1-0-alk-1’-enyl-2-acyl-sn-glycerol) and alkyl-acylphospholipids ("plasmanylphospholipid"). This class of lipids have important roles in human cell signaling and structure.

Lingual lipase is a member of a family of digestive enzymes called triacylglycerol lipases, EC 3.1.1.3, that use the catalytic triad of aspartate, histidine, and serine to hydrolyze medium and long-chain triglycerides into partial glycerides and free fatty acids. The enzyme, released into the mouth along with the saliva, catalyzes the first reaction in the digestion of dietary lipid, with diglycerides being the primary reaction product. However, due to the unique characteristics of lingual lipase, including a pH optimum 4.5–5.4 and its ability to catalyze reactions without bile salts, the lipolytic activity continues through to the stomach. Enzyme release is signaled by the autonomic nervous system after ingestion, at which time the serous glands under the circumvallate and foliate papillae on the surface of the tongue secrete lingual lipase into the grooves of the papillae, co-localized with fat taste receptors. The hydrolysis of the dietary fats is essential for fat absorption by the small intestine, as long chain triacylglycerides cannot be absorbed, and as much as 30% of fat is hydrolyzed within 1 to 20 minutes of ingestion by lingual lipase alone.

Lingual lipase, together with gastric lipase, comprise the two acidic lipases.

Diacylglycerol oil (DAG oil) is a cooking oil in which the ratio of triglycerides, also known as Triacylglycerols (TAGs), to diacylglycerols (DAGs) is shifted to contain mostly DAG, unlike conventional cooking oils, which are rich in TAGs. Vegetable DAG oil, for example, contains 80% DAG and is used as a 1:1 replacement for liquid vegetable oils in all applications.

Very-low-density lipoprotein (VLDL), density relative to extracellular water, is a type of lipoprotein made by the liver. VLDL is one of the five major groups of lipoproteins (chylomicrons, VLDL, intermediate-density lipoprotein, low-density lipoprotein, high-density lipoprotein) that enable fats and cholesterol to move within the water-based solution of the bloodstream. VLDL is assembled in the liver from triglycerides, cholesterol, and apolipoproteins. VLDL is converted in the bloodstream to low-density lipoprotein (LDL) and intermediate-density lipoprotein (IDL). VLDL particles have a diameter of 30–80 nanometers (nm). VLDL transports endogenous products, whereas chylomicrons transport exogenous (dietary) products. In the early 2010s both the lipid composition and protein composition of this lipoprotein were characterised in great detail.

Lipid metabolism is the synthesis and degradation of lipids in cells, involving the breakdown and storage of fats for energy and the synthesis of structural and functional lipids, such as those involved in the construction of cell membranes. In animals, these fats are obtained from food and are synthesized by the liver. Lipogenesis is the process of synthesizing these fats. The majority of lipids found in the human body from ingesting food are triglycerides and cholesterol. Other types of lipids found in the body are fatty acids and membrane lipids. Lipid metabolism is often considered the digestion and absorption process of dietary fat; however, there are two sources of fats that organisms can use to obtain energy: from consumed dietary fats and from stored fat. Vertebrates (including humans) use both sources of fat to produce energy for organs such as the heart to function. Since lipids are hydrophobic molecules, they need to be solubilized before their metabolism can begin. Lipid metabolism often begins with hydrolysis, which occurs with the help of various enzymes in the digestive system. Lipid metabolism also occurs in plants, though the processes differ in some ways when compared to animals. The second step after the hydrolysis is the absorption of the fatty acids into the epithelial cells of the intestinal wall. In the epithelial cells, fatty acids are packaged and transported to the rest of the body.

Metabolic processes include lipid digestion, lipid absorption, lipid transportation, lipid storage, lipid catabolism, and lipid biosynthesis.Lipid catabolism is accomplished by a process known as beta oxidation which takes place in the mitochondria and peroxisome cell organelles.