Definition of Lipids in Biochemistry
Other types of lipids include sucolipids (fatty acids associated with a sugar backbone) and polyketides (compounds formed by polymerization of the acetyl and propionyl subunits). Lipids, one of a diverse group of organic compounds, including fats, oils, hormones, and some components of membranes grouped together because they do not interact significantly with water. One type of lipid, triglycerides, is bound to fat in fat cells, which serve as an energy storage repository for organisms and also provide thermal insulation. Some lipids, such as steroid hormones, serve as chemical messengers between cells, tissues, and organs, and others communicate signals between biochemical systems within a single cell. Cell membranes and organelles (structures inside cells) are microscopically thin structures formed from two layers of phospholipid molecules. Membranes are used to separate individual cells from their environment and to divide the inside of the cell into structures that perform special functions. This compartmentalization function is so important that the membranes and the lipids they form must have been essential to the origin of life itself. The name phospholipid is derived from the fact that phosphoacylglycerols are lipids containing a phosphate group. Plant thylakoid membranes have the largest lipid component of a non-bilayer monogalactosyl diglyceride (MGDG) and low in phospholipids; Despite this unique lipid composition, chloroplast thylakoid membranes have been shown to contain a dynamic lipido-bilayer matrix, as shown by magnetic resonance and electron microscope studies. [58] Let`s examine in detail the structure of lipids, properties, types and classification of lipids.
Glycerin is a type of lipid that consists of glycerol, which is aesthetically bound to a fatty acid. One of the best-known glycerolipids is a triglyceride (also called triacylglycerol). Triglyceride is a high-energy compound composed of glycerol and three fatty acids (hence its name). Lipids are a diverse group of compounds and perform many different functions. At the cellular level, phospholipids and cholesterol are some of the main components of the membranes that separate a cell from its environment. Lipid-derived hormones, known as steroid hormones, are important chemical messengers and include testosterone and estrogen. At the level of the body, triglycerides stored in fat cells serve as energy storage deposits and also provide thermal insulation. Although the term “lipid” is sometimes used as a synonym for fats, fats are a subset of lipids called triglycerides. Lipids also include molecules such as fatty acids and their derivatives (including tri-, di-, monoglycerides and phospholipids), as well as other metabolites containing sterols such as cholesterol. [7] Although humans and other mammals use different biosynthetic pathways to break down and synthesize lipids, some essential lipids cannot be made this way and must be obtained from food. Non-hydrolyzable lipids lack such functional groups and include steroids and fat-soluble vitamins (A, D, E and K).
In 1947, T. P. Hilditch defined “simple lipids” as fats and waxes (real waxes, sterols, alcohols). Lipids are molecules that contain hydrocarbons and form the building blocks of the structure and function of living cells. Examples of lipids include fats, oils, waxes, certain vitamins (such as A, D, E and K), hormones, and most of the cell membrane that is not composed of proteins. Examples of glycerophospholipids found in biological membranes include phosphatidylcholine (also known as PC, GPCho or lecithin), phosphatidylethanolamine (PE or GPEtn) and phosphatidylserine (PS or GPSer). Some glycerophospholipids in eukaryotic cells, such as phosphatidylinositile and phosphatidic acids, not only serve as the main component of cell membranes and binding sites for intra- and intercellular proteins, but are also precursors or even second messengers derived from the membrane. [31]: 844 Typically, one or both of these hydroxyl groups are acylated with long-chain fatty acids, but there are also glycerophospholipids bound to alkyls and 1Z-alkenyl (plasmalogs) as well as variants of dialkyl ether in archaebacteria. [38] Glycerolipids are made up of mono-, di- and trisubstituted glycerols,[30] The fatty acid triesters of glycerol, called triglycerides, are the best known. The word “triacylglycerin” is sometimes used as a synonym for “triglycerides”. In these compounds, the three hydroxyl groups of glycerol are each esterified, usually by different fatty acids. Since they act as energy reserves, these lipids make up the majority of the storage fat in animal tissues.
The hydrolysis of triglyceride ester bonds and the release of glycerin and fatty acids from adipose tissue are the first steps in fat metabolism. [31]: 630–1 Scientists sometimes define lipids as small hydrophobic or amphiphilic molecules; The amphiphilic nature of some lipids allows them to form structures such as vesicles, multilamellar/unilamellar liposomes or membranes in an aqueous environment. Biological lipids come entirely or partially from two different types of biochemical subunits or “building blocks”: the ketoacyl and isoprene groups. [4] With this approach, lipids can be divided into eight categories: fatty acids, glycerolipids, glycerophospholipids, sphingolipids, sucolipids and polyketides (derivatives of the condensation of ketoacyl subunits); and sterollipids and prenollipids (derived from the condensation of isoprene subunits). [4] Lipids are used directly or synthesized from fats in the diet. There are many biosynthetic pathways to break down and synthesize lipids in the body. Lipids include fatty acids, neutral fats, waxes, and steroids (such as cortisone). Compound lipids (lipids complexed with another type of chemical compound) include lipoproteins, glycolipids and phospholipids.
Other subclasses of glycerols are represented by glycosylglycerols characterized by the presence of one or more sugar residues bound to glycerol via a glycosidic bond. Examples of structures in this category are digalactosyldiacylglycerols in plant membranes[32] and seminolipids in mammalian spermatozoa. [33] Lipidomics research has shown that acne often shows changes in lipids on the skin surface: higher levels of glycerophospholipids, fatty acylene and sterile, and lower levels of prelollipids and sucolipids. One study also reported shorter ceramide chain lengths in men with acne. Within these two main classes of lipids, there are many specific types of lipids that are important for life, including fatty acids, triglycerides, glycerophospholipids, sphingolipids, and steroids. These are roughly classified as simple lipids and complex lipids. Sterols, such as cholesterol and its derivatives, are an important component of membrane lipids[43], along with glycerophospholipids and sphingomyelins. Other examples of sterols are bile acids and their conjugates,[44] which are oxidized derivatives of cholesterol in mammals and are synthesized in the liver. Plant equivalents are phytosterols, such as β-sitosterol, stigmasterol and brassicasterol; The latter compound is also used as a biomarker of algae growth. [45] The predominant sterol in fungal cell membranes is ergosterol. [46] Glycerophospholipids are the most frequently cited lipid examples in textbooks because they form the lipid bilayer of cell membranes. A prelollipid is a type of lipid synthesized from isopentenyl diphosphate and dimethylallyl diphosphate by the mevalonic acid pathway.
Simple isoprenoids (e.g., carotenoids) are prenollipids. Fatty acids (including fats) are a subset of lipids. Fat, in particular, is a triglyceride (lipid) that is usually solid at room temperature. Therefore, it will be inaccurate to consider the two terms as synonymous. Sucolipids describe compounds in which fatty acids are associated with a sugar backbone and form structures compatible with membrane bilayers. In sucolipids, a monosaccharide replaces the glycerol backbone present in glycerolipids and glyceropholipids. The best known sucolipids are the acylated glucosamine precursors of lipid A composing lipopolysaccharides in Gram-negative bacteria. Typical A lipid molecules are glucosamine disaccharides, which are derived with up to seven fatty acyl chains. The minimal lipopolysaccharide used for the growth of E. coli coli is the lipid A Kdo2, a hexa-acylated disaccharide of glucosamine, which is glycosylated with two radicals of 3-deoxy-D-manno-octulosonic acid (Kdo). [52] Sphingolipids do not always contain glycerin.
Their defining feature is the presence of amino acids (spine of the sphingoid base) and a long-chain fatty acyl-CoA. A non-saponifiable lipid cannot be broken down into smaller molecules by hydrolysis. Non-saponifiable lipids include cholesterol, prostaglandins, etc. Fatty acids are crucial components of all these lipids. Lipid n., plural: lipids [ˈlɪpɪd or ˈlaɪ pɪd] Description: biomolecule characterized by its insoluble in water, such as fats, oils, sterols, triglycerides This molecule could also contain proteins, phosphoric acid and sugars. Sphingolipids have been shown to affect the structure of cell membranes and define how these membranes interact with surrounding fluids and cells; They also help to form phagoman vesicles. Probably. It`s very, very exceptional.
I like the details better. I want to thank everyone who published this lesson and those who actually wrote it. It`s great. This builds a beautiful understanding for the students. I mean, just like me. I`ve hated lipids since I was in ninth grade. and now I`m in my first year. And now that I`ve learned from this site.
I think biology is my favorite subject and lipids are my favorite subject. Thank you again to all of you. One group of sphingolipids are ceramides, which are often found in skin care products.