In biology and biochemistry, a lipid is a biomolecule that is soluble in nonpolar solvents. Non-polar solvents are hydrocarbons used to dissolve other hydrocarbon lipid molecules that do not dissolve in water, including fatty acids, waxes, sterols, fat-soluble vitamins, monoglycerides, diglycerides, triglycerides, and phospholipids.
Nicotinamide adenine dinucleotide phosphate, abbreviated NADP+ or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NADPH as a reducing agent ('hydrogen source'). It is used by all forms of cellular life.
Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism.
Fatty acid metabolism consists of various metabolic processes involving or closely related to fatty acids, a family of molecules classified within the lipid macronutrient category. These processes can mainly be divided into (1) catabolic processes that generate energy and (2) anabolic processes where they serve as building blocks for other compounds.
Dihydroxyacetone phosphate (DHAP, also glycerone phosphate in older texts) is the anion with the formula HOCH2C(O)CH2OPO32-. This anion is involved in many metabolic pathways, including the Calvin cycle in plants and glycolysis. It is the phosphate ester of dihydroxyacetone.
Glycerophospholipids or phosphoglycerides are glycerol-based phospholipids. They are the main component of biological membranes. Two major classes are known: those for bacteria and eucaryote and a separate family for archaea.
Glycerophospholipids of biochemical relevance are divided into three subclasses based on the substitution present at the sn-1 position of the glycerol backbone: acyl, alkyl and alkenyl. Of these, the alkyl and alkenyl moiety in each case form an ether bond, which makes for two types of ether phospholipids, plasmanyl, and plasmenyl. Plasmalogens are plasmenyls with an ester linked lipid at the sn-2 position of the glycerol backbone, chemically designated 1-0(1Z-alkenyl)-2-acyl-glycerophospholipids. The lipid attached to the vinyl ether at sn-1 can be C16:0, C18:0, or C18:1, and the lipid attached to the acyl group at sn-2 can be C22:6 ω-3 or C20:4 ω-6, . Plasmalogens are classified according to their head group, mainly as PC plasmalogens (plasmenylcholines) and PE plasmalogens (plasmenylethalomines) Plasmalogens should not be confused with plasmanyls.
In an organic chemistry general sense, an ether lipid implies an ether bridge between an alkyl group and an unspecified alkyl or aryl group, not necessarily glycerol. If glycerol is involved, the compound is called a glyceryl ether, which may take the form of an alkylglycerol, an alkyl acyl glycerol, or in combination with a phosphatide group, a phospholipid.
Lipid metabolism is the synthesis and degradation of lipids in cells, involving the breakdown or 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 or 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 as 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 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.
sn-Glycerol 3-phosphate is the organic ion with the formula HOCH2CH(OH)CH2OPO32-. It is one of three stereoisomers of the ester of dibasic phosphoric acid (HOPO32-) and glycerol. It is a component of glycerophospholipids. From a historical reason, it is also known as L-glycerol 3-phosphate, D-glycerol 1-phosphate, L-α-glycerophosphoric acid.
The glycerol-3-phosphate shuttle is a mechanism that regenerates NAD+ from NADH, a by-product of glycolysis. The shuttle consists of the sequential activity of two proteins: GPD1 which transfers an electron pair from NADH to dihydroxyacetone phosphate (DHAP), forming glycerol-3-phosphate (G3P) and regenerating NAD+ needed to generate energy via glycolysis. The mitochondrial inner membrane protein GPD2 catalyzes the oxidation of G3P, regenerating DHAP in the cytosol and forming FADH2 in the mitochondrial matrix. In mammals, its activity in transporting reducing equivalents across the mitochondrial membrane is considered secondary to the malate-aspartate shuttle.
Glycerol-3-phosphate dehydrogenase (GPDH) is an enzyme that catalyzes the reversible redox conversion of dihydroxyacetone phosphate to sn-glycerol 3-phosphate.
Phosphatidylglycerol is a glycerophospholipid found in pulmonary surfactant and in the plasma membrane where it directly activates lipid-gated ion channels.
In enzymology, a sn-glycerol-1-phosphate dehydrogenase (EC 1.1.1.261) is an enzyme that catalyzes the chemical reaction
In enzymology, a glycerol-3-phosphate dehydrogenase (NAD+) (EC 1.1.1.8) is an enzyme that catalyzes the chemical reaction
In enzymology, a glycerol-3-phosphate dehydrogenase [NAD(P)+] (EC 1.1.1.94) is an enzyme that catalyzes the chemical reaction
Archaeol is composed of two phytanyl chains linked to the sn-2 and sn-3 positions of glycerol. As its phosphate ester, it is a common component of the membranes of archaea.
2-acyl-sn-glycero-3-phosphocholines are a class of phospholipids that are intermediates in the metabolism of lipids. Because they result from the hydrolysis of an acyl group from the sn-1 position of phosphatidylcholine, they are also called 1-lysophosphatidylcholine. The synthesis of phosphatidylcholines with specific fatty acids occurs through the synthesis of 1-lysoPC. The formation of various other lipids generates 1-lysoPC as a by-product.
Glycerol-3-phosphate dehydrogenase (EC 1.1.5.3 is an enzyme with systematic name sn-glycerol 3-phosphate:quinone oxidoreductase. This enzyme catalyses the following chemical reaction
CDP-archaeol synthase is an enzyme with systematic name CTP:2,3-bis-O-(geranylgeranyl)-sn-glycero-1-phosphate cytidylyltransferase. This enzyme catalyses the following chemical reaction
