biochemistry Chapter 2 lipid

Lipids

A heterogeneous group of naturally occurring organic compounds that are insoluble in water and soluble in organic solvents.

Fats and oils

Lipids that are widely distributed in plant and animal tissues and serve as a source of energy for the body.

Phospholipids

Lipids that are major structural components of membranes and form impermeable barriers in cells.

Cholesterol

A sterol that is a precursor of steroid hormones and an important component of plasma membranes.

Fat soluble vitamins

Vitamins (A, D, E, and K) that are absorbed with the help of lipids.

Bile acids

Derived from cholesterol, these act as emulsifying agents and facilitate the digestion and absorption of lipids.

Simple lipids

Esters of fatty acids with different alcohols.

Neutral lipids

Esters of fatty acids with glycerol, including monoacylglycerol, diacylglycerol, and triacylglycerol.

Triglyceride

The major storage and transport form of fatty acids, consisting of three fatty acids esterified to glycerol.

Mixed triglycerides

Triglycerides containing two or three different fatty acids.

Fats

Solid triglycerides obtained from animal sources, rich in saturated fatty acids.

Oils

Liquid triglycerides obtained from plant sources, rich in unsaturated fatty acids.

Hydrolysis

The process of breaking down triacylglycerols into fatty acids and glycerol.

Saponification

The reaction of triglycerides with strong bases to form carboxylate salts of fatty acids, called soaps.

Micelles

Spherical clusters formed by fatty acids in aqueous solutions, important for the transport of insoluble lipids in the blood.

Fatty acids

Long hydrocarbon chains with a terminal carboxylic acid group, obtained from the hydrolysis of lipids.

Saturated fatty acids

Fatty acids with all carbon atoms in the chain saturated with hydrogen atoms.

Monounsaturated fatty acids

Fatty acids with one double bond in their structure.

Polyunsaturated fatty acids

Fatty acids with two or more double bonds in their structure.

Cis-configuration

The arrangement of double bonds in a fatty acid that causes a bend or kink in the fatty acid chain.

Nomenclature

The system of naming fatty acids based on their carbon numbering and position of double bonds.

Trivial name

Common name of a fatty acid.

Systemic name

Official name of a fatty acid used in nomenclature.

IUPAC

International Union of Pure and Applied Chemistry, the organization responsible for standardizing chemical nomenclature.

Carboxyl carbon

The carbon atom in a fatty acid chain that is part of the carboxyl group.

α carbon

The carbon atom adjacent to the carboxyl carbon in a fatty acid chain.

β, γ, δ carbons

The carbon atoms following the α carbon in a fatty acid chain.

ω carbon

The carbon atom farthest from the carboxyl carbon in a fatty acid chain.

Saturated fatty acids

Fatty acids with no double bonds in their carbon chain.

Unsaturated fatty acids

Fatty acids with one or more double bonds in their carbon chain.

Double bond

A chemical bond between two carbon atoms in a fatty acid chain.

C-System

A system of designating the position of double bonds in a fatty acid chain, with the carbonyl carbon as C-1.

ω-System

A system of designating the position of double bonds in a fatty acid chain, with the terminal methyl carbon as ω.

Omega-6 Fatty Acids

Fatty acids with the first double bond at carbon 6.

Omega-3 Fatty Acids

Fatty acids with the first double bond at carbon 3.

Melting temperature

The temperature at which a substance changes from a solid to a liquid state.

Essential fatty acids

Fatty acids that cannot be synthesized in the body and must be obtained from the diet.

Linoleic acid

An essential fatty acid with two double bonds.

Linolenic acid

An essential fatty acid with three double bonds.

Arachidonic acid

An essential fatty acid and precursor of eicosanoids.

Eicosanoids

A class of hormone-like molecules derived from arachidonic acid.

Prostaglandins

A group of eicosanoids involved in various body processes.

Leukotrienes

A group of eicosanoids involved in the inflammatory response.

Thromboxanes

A group of eicosanoids involved in blood clotting.

Lipoxins

A group of eicosanoids with anti-inflammatory properties.

Waxes

Esters of long-chain fatty acids with long-chain alcohols.

Triacylglycerols

A type of lipid composed of three fatty acids esterified to a glycerol molecule.

Protective coatings

Waxes found on skin, fur, feathers, leaves, fruits, and exoskeletons.

Sebum

An oily substance secreted by sebaceous glands in the skin, containing waxes.

Complex lipids

Lipids that contain additional groups, such as phosphoric acid or prosthetic groups.

Compound lipids

Lipids that are esters of fatty acids with alcohol and contain additional groups.

Phospholipids

Lipids that contain fatty acids, alcohol, and phosphoric acid residue as additional groups.

Glycerophospholipids

Phospholipids that contain glycerol as the alcohol component.

Sphingophospholipids

Phospholipids that contain sphingosine as the alcohol component.

Amphipathic

Having both a polar and nonpolar end.

Phosphatidylcholine (Lecithin)

A glycerophospholipid with choline as the alcohol component.

Phosphatidylethanolamine (Cephalin)

A glycerophospholipid with ethanolamine as the alcohol component.

Phosphatidylinositol

A glycerophospholipid with inositol as the alcohol component.

Phosphatidylinositol bisphosphate (PIP2)

A phospholipid present in cell membranes that plays a vital role in hormone action on cell membranes.

Phosphatidylglycerol (Cardiolipin)

A phospholipid found in mitochondrial membranes and myocardium.

Phosphatidyl glyceracetals (Plasmalogens)

Phospholipids with an aliphatic long chain unsaturated in C-1, esterified to a fatty acid in C-2, and attached to cholin, ethanol amine, or serine in C-3. Found in cell membranes in the brain, muscle, and seeds of higher plants.

Phosphoglycerides

Phospholipids that serve various biological functions, including being major components of biological membranes and sub-cellular organelles, regulating the permeability of cell membranes, maintaining protoplasmic structure, transporting other lipids in the bloodstream, and acting as donors of arachidonic acid for the synthesis of prostaglandins and thromboxanes.

Sphingophospholipids

Phospholipids derived from alcohol sphingosine instead of glycerol, serving as structural components of cell membranes.

Sphingomyelins

Phospholipids containing sphingosine, one molecule of fatty acid, phosphoric acid, and choline. Found in most animal cell membranes and in abundance in the myelin sheath of the central nervous system.

Glycolipids

Molecules containing carbohydrate and lipid. When glycolipids contain sphingosine, they are called glycosphingolipids. Found in all membranes in the body, with the simplest form being cerebrosides.

Sulfolipids

Lipids in which a sulfonated glucose residue is joined to a diacylglycerol in glycosidic linkage. Found in plant membranes.

Gangliosides

Glycolipids with oligosaccharide groups, including N-acetylneuraminic acid (sialic acid). Major constituents of most mammalian plasma membranes, particularly in brain cells.

Lipoproteins

Molecules containing lipid and protein responsible for the transport of lipid molecules through the bloodstream. Classified into chylomicrons, very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL).

Cholesterol

The major sterol in animal tissues, serving as a major structural constituent of cell membranes and plasma lipoproteins. Also a precursor in the biosynthesis of steroid hormones, vitamin D, and bile salts.

Terpenes

Lipids formed from the combination of two or more molecules of isoprene units. Monoterpenes consist of two isoprene units, sesquiterpenes consist of three isoprene units, and diterpenes consist of four isoprene units, and so on.

Rancidity

Unpleasant odor and taste in fats and oils when stored for a long time. Can be caused by hydrolytic rancidity, which is the growth of microorganisms that secrete lipases and split triglycerides into mono- and diglycerides, glycerol, and fatty acids.

Oxidative rancidity

The process in which unsaturated fatty acids undergo autooxidation, resulting in the formation of short chain acids and aldehydes with rancid taste and odors.

Autooxidation

The spontaneous reaction of unsaturated fatty acids with oxygen, leading to oxidative rancidity.

Antioxidant

A compound, such as vitamin E, that can be added to prevent oxidative rancidity by inhibiting the oxidation of unsaturated fatty acids.

Cleavage

The process in which oxygen adds to the double bonds of unsaturated fatty acids, resulting in the breaking of the bonds and the formation of shorter chain compounds.