HISTORICAL PERSPECTIVES ON LIPID BIOCHEMISTRY. JOURNAL Lipids are often broadly, and poorly, defined as biomolecules that are insoluble in. 1. Structure and Classification of Lipids. ◇ Lipids are naturally occurring molecules from plants or animals that are soluble in nonpolar organic solvents. Lipids. Lipids are organic compounds that contain hydrocarbons which are the foundation for the structure and function of living cells. Lipids are.

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Biochemistry Lecture Slide 2. Lipids. Lipids are distinguished by their high solubility in non polar solvents and low solubility in H. 2. O. ○. Diverse. LIPIDS. • A class of biological molecules (i.e., are of biological origin) defined by low solubility in water and high solubility in non-polar solvents (such as. Chapter 8 Lecture Notes: Lipids. Educational Goals. 1. Know the factors that characterize a compound as being a lipid. 2. Describe the structure of fatty acids .

The membrane is an amphipathic sheet-like structure that is fluid and electrically polarized. The membrane itself has little functions, but the proteins that are integrally and peripherally integrated to the membrane help mediate many of the functions that we contribute to membrane.

lipids biochemistry notes, Study notes for Medical Biochemistry

The membrane is asymmetric in that the proteins are randomly distributed across the membrane, some are attached inside the cell, some outside, and others integrated within membrane.

Also, rapid lateral diffusion and slow transverse diffusion contribute both to the membrane's asymmetric characteristic and fluidity. In transverse diffusion, phospholipids are flipped inside-out or outside-in, and this flipping is regulated by flipases.

However, the longer the fatty acid chains are, the less likely for transverse diffusion to occur. Longer chains also decreases the fluidity of the plasma membrane. There are other factors that may affect plasma membrane's fluidity. For example, the better arranged the fatty acids chains are, the less fluid the membrane is.

On top of that, the more unsaturated the fatty acids are, the more fluid the membrane is. This is because the double bonds bend the chains that allows sloppy arrangements. The interruption of cholesterol within the membrane also causes more fluidity since the polar hydroxy group in cholesterol disrupts the hydrophobic environment within the phospholipid bilayer.

Glycolipids[ edit ] Glycolipids are sugar glyco- containing lipids. They are derived from sphingosine instead of a form of phospholipids that derives from glycerol phospholipids exist in both derivatives from glycerol and sphingomyelin platform. Another difference from phospholipids is that glycolipids contain a sugar unit can be glucose or galactose instead of a phosphate group.

Examples: Glycolipid molecules exist from the most basic molecule, cerebroside which contains 1 fatty acid unit, a sphingosine backbone, and 1 sugar unit glucose or galactose , to the most complex molecules containing branched chains of multiple sugar residues up to seven residues in gangliosides.

Properties: When glycolipids exist in membranes, their sugar residue terminal always face the extracellular side. Chemical structure of Glycolipids Cholesterol[ edit ] Cholesterol Cholesterol is a form of lipids that differs from the rest of its relatives. It is relatively medium molecule that contains 4 adjacent cyclic hydrocarbon molecules with three six-member rings and one five-member ring that has a hydroxyl and a saturated hydrocarbon chain terminals.

When exist in membranes, the 4 cyclic molecules in the cholesterol molecule lay parallel to the fatty acid chains of the phospholipids, meanwhile the hydroxyl terminal points in the direction with the polar phospholipid heads in which it interact with.

Cholesterol molecules exist primarily in nerve cells. The molecule binds to the myelin sheath membrane which provides an outer coating that protects the nerve cell from its surroundings.

It is an essential predecessor to sex hormones that exists in males testosterone and females oestradiol. Also an essential component in vitamin D that enables the body to utilize calcium to form bones. Animals acquire very little cholesterol from the food they eat; they make cholesterol within the body. Although cholesterol is essential for many processes and structural function, it can be detrimental to have excess cholesterol.

Too much cholesterol in the blood will cause blockages in the arteries which can result in heart disease, high blood pressure, and stroke. Only 0. Membrane Properties[ edit ] The cell membrane has a set of properties that are contributed to the presences of the lipids as well as proteins.

Structures are lik sheets. They are formed by lipids, proteins, and carbohydrates.

The membrane is amphipathic contain hydrophobic and hydrophilic regions. Each protein allows for the function of the membrane. Membranes are held on by weak, non-covalent bonds. The structure is asymmetric. It is high in fluidity. The membrane is polarized.

Fluidity[ edit ] Lipid unsaturation effect The presence of the lipids in the membrane structure of a cell is vital for the cell especially affecting its fluidity. As addressed in the section below, this is necessary to allow things to flow in and out of the cell. One factor that plays a big role in this is cholesterol as shown below.

Another one is the presence of double bonds. The more the double bonds, the greater the amount of kinks or curve in the lipid and therefore more free space.

The length of the lipids also plays a role. Lipids move in two distinct ways. It also explains how living organisms obtain fatty acids, both from their diets and through metabolic breakdown of stored fats.

Start your free trial today for unlimited access to Britannica. Structure Biological fatty acids, members of the class of compounds known as carboxylic acids , are composed of a hydrocarbon chain with one terminal carboxyl group COOH. The fragment of a carboxylic acid not including the hydroxyl OH group is called an acyl group.

Most biological fatty acids contain an even number of carbon atoms because the biosynthetic pathway common to all organisms involves chemically linking two-carbon units together although relatively small amounts of odd-number fatty acids do occur in some organisms.

Although the molecule as a whole is water-insoluble by virtue of its hydrophobic hydrocarbon chain, the negatively charged carboxylate is hydrophilic.

This common form for biological lipids—one that contains well-separated hydrophobic and hydrophilic parts—is called amphipathic.

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They are more palatable and storable to unlimited amount compared to carbohydrates. Supply the essential fatty acids that cannot be synthesized by the body. Supply the body with fat-soluble vitamins A, D, E and K. They are important constituents of the nervous system.

Tissue fat is an essential constituent of cell membrane and nervous system. It is mainly phospholipids in nature that are not affected by starvation. This reaction is used for detection of free glycerol or any compound containing glycerol. Fatty AcidsDefinition: Saturated Fatty acids could be: A-Short chain Saturated F.

B-Long chain Saturated F. A-Monounsaturated fatty acids: Essential fatty acids: Their deficiency in the diet leads to nutrition deficiency disease. They enter in structure of all cellular and subcellularmembranes and the transporting plasmaphospholipids.

Com pound or c onj ugat ed l i pi ds3.


Der i ved Li pi ds4. T y p e s o f t r ig ly c e r id e s1-Simple triglycerides: If the three fatty acids connected to glycerol are of the same type the triglyceride is called simple triglyceride, e. Any color, or taste is due to association with other foreign substances, e. Advantages for hydrogenated oil or fat are as follows: It is more pleasant as cooking fat.

It is digestible and utilizable as normal animal fats and oils. It is less liable to cause gastric or intestinal irritation.

lipids biochemistry notes, Study notes for Medical Biochemistry

It is easily stored and transported and less liable to rancidity. Hydrolytic rancidity3. Oxidative rancidity4. Ketonic rancidity1-Hydrolytic rancidity: Polyunsaturated fatty acid Oxidant, O2 Peroxyradical Cyclic peroxide Hydroperoxide Aldehydes Hydroxy fatty acidsuch as malondialdehyde Other fragments such as dicarboxylic acids They include phenols, naphthols, tannins andhydroquinones.

The most common natural antioxidant is vitaminE that is important in vitro and in vivo. Hazards of Rancid Fats: Checking the purity of fat for detection of adulteration.

To quantitatively estimate certain properties of fat. To identify the biological value and natural characteristics of fat. Detection of fat rancidity and presence of toxic hydroxy fatty acids. It is the number of grams of iodine absorbed by grams of fat or oil.

It is a measure for the degree of unsaturation of the fat, as a natural property for it. It is the number of Definition milligrams of KOH required to completely saponify one gram of fat.Essays Biochem.

Bile acids. It is more pleasant as cooking fat. As their percentage increases, the liability to atherosclerosis increases. Journal of the Science of Food and Agriculture In transverse diffusion, phospholipids are flipped inside-out or outside-in, and this flipping is regulated by flipases. Fatty AcidsDefinition:

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