12 Bio Lipids 2014

Fats, Oils, Phospholipids, Waxes, Steroids, SoapsBL10A HALL 2006*

BL10A HALL 2006

Lipids OutlineLipids (structure and function) Structure (components) & properties Saturated and unsaturated fatty acids Phospholipids, micelles Steroids, cholesterolBL10A HALL 2006*

BL10A HALL 2006

Objectives At the end of this lesson you should be able to:Lipids (structure and function)Describe the structure of triglycerides and their componentsDifferentiate between saturated and unsaturated fatty acidsDescribe the structure of phospholipids, steroids. State the function and properties of different types of lipids.

BL10A HALL 2006*

BL10A HALL 2006

LipidsConsist of C, H and O; Have less O atoms but more C-H bonds than carbohydrates.

Non-polar, so do not dissolve in waterVital component of membranes that divide one aqueous compartment in the body from another.BL10A HALL 2006*

BL10A HALL 2006

LipidsWill dissolve in non-polar substances such as alcohols, acetone, ether and chloroform.

source of energy Lipids act as energy storage molecules in plants, animals and other organisms. Involved in insulation and structural support. *

Lipids =Fats and OilsFats commonly formed by animals; solid at room temperature

Oils commonly formed by plants; liquid at room temperature.

*

Lipids = Fats and OilsBelong to the chemical group called esters

Compounds formed by reaction between an alcohol and an acid.

Usually made from glycerol (3 C alcohol) and fatty acids in living things

*

Forming lipids - GlycerolGlycerol 3 C molecule with each C bearing a OH (hydroxyl) group. The C atoms form the backbone of the fat molecule. *

Forming lipids - GlycerolHas three sites available to form ester linkages with fatty acids.

Forms monoglyceride, diglyceride, or tri-glycerides depending on whether it is bound to one, two, or three fatty acids. Also called (monoacylglycerol, diacylglycerol or tri-acylglycerol)*

Forming lipids Fatty AcidsFatty acid A long chain of C and H atoms (hydrocarbon chain) with a carboxyl group at one end. Length varies Nature of the fatty acids determines the nature of the fat formed Approximately 30 different fatty acids are common in lipids*

Forming lipids Fatty AcidsSaturated fatty acids No double bonds between any C atoms. Contains maximum possible number of H atoms; solid at room temperature. All possible bonds are used. *

Forming lipids Fatty AcidsUnsaturated fatty acids Have 1 double bonds. Triglycerides have many.Tend to be oils at room temperature because They have a lower melting pointThe chains are harder to pack closer together due to kinks in the tail. *

BL10A HALL 2006

Fatty Acids - Symbols*SaturatedUnsaturated

BL10A HALL 2006

Forming lipids Fatty AcidsThe carboxyl end of a fatty acid molecule is hydrophilic will dissolve in aqueous solutions in the cell

The hydrocarbon chain is hydrophobic. will attach to or dissolve in nonpolar organic compounds.

*hydrophilic headhydrophobic tail

Forming lipids Fatty AcidsFatty acids tend to lie along interfaces between nonpolar and aqueous environments whichmakes them important components of cell membranes that divide living systems into compartments.is the source of the cleaning power of soaps and detergents.Washing: the hydrophilic part of the soap molecule interacts with the water while the hydrophobic "greasy" end of the soap molecule attaches itself to the grease, letting water seep in around it. The grease is loosed and surrounded by soap molecules, which are rinsed off by water.*

Fatty AcidsSeldom occur free; Usually combined with other molecules to form substances such asGlycolipids (carbohydrate + lipid) Lipoproteins (lipid + protein).

Or are monomers of more complex lipids.*

FATS: MonoglyceridesOne fatty acid joined to glycerol results in a Monoglyceride.The one fatty acid can be joined on any of the 3 carbons on glycerol.*Alpha monogyceride fatty acid joined to first carbon Beta monoglyceride fatty acid joined to second carbon

BL10A HALL 2006

FATS: Diglycerides Formed when two fatty acid are joined to glycerol.The fatty acids can be the same or different.*, diglyceride fatty acid joined to first and last carbon of glycerol, diglyceride - fatty acid joined to first or last and second carbon

Triglycerides

Consists of one molecule glycerol attached to 3 fatty acid molecules (same or different from each other) by ester linkages.The 3 alcohol (OH) groups of the glycerol have reacted with the carboxyl (COOH) groups of three fatty acids. 3 molecules of water have been removed.

*

TriglyceridesAlso called triacylglycerol (TAG); Triglycerides are what is usually referred to as FatsMajor function of fats = Energy Storage.

*

TriglyceridesMay be solid or liquid at normal room temperatures. Solids are called "fats" or "butters"Liquids are called "oils"Main constituents of vegetable oils and animal fats.Have lower densities than water (they float on water)

*

TrigylceridesAnimals that live in cold habitats, such as fish in the Artic and Antarctic, usually contain triglycerides that are less saturated than those of animals from warmer areas. If they did not, their bodies would become rigid at the low temperatures they encounter.Unsaturated fats have looser chains and lower melting points.*

SaponificationSoap productionTriglycerides are reacted with sodium or potassium hydroxide to produce glycerol and a fatty acid salt, called 'soap'. Natural soaps are sodium or potassium salts of fatty acids. *

*Saponificationglycerol, ester bond, fatty acid

SoapsAlkali metal salts of fatty acids (soaps) are more soluble in water than the fatty acids themselves. Soaps have a nonpolar hydrocarbon chain, the "tail", and a polar (often ionic) "head group". Their use as cleaning agents is facilitated by their surfactant character, which lowers the surface tension of water.

*

SoapsPolar end of the soap molecule is attracted to waterHydrophobic end is attracted to oil, grease, soil but is repelled by water. Soaps are able to emulsify (disperse in water) and hold the dirt or oil in suspension until it can be washed away.*

Phospholipids

Lipids in which one of the fatty acid groups is replaced by a phosphate groupTherefore consist of glycerol + 2 fatty acids + 1 phosphate group. Phosphate is hydrophilic; Hydrocarbon chain of fatty acid hydrophobic. Important property in cell membrane formation and function where they phospholipids form bilayers.*

Phospholipid Structure*Fatty acidFatty acid Glycerol Phosphate groupEster linkage

Structure Of A Phospholipid: Phosphatidyl choline*Additional small charged or polar molecules (eg. Choline, Serine, Inositol) may be linked to negatively charged phosphate group leading to a variety of phospholipids.

Phospholipids Relations with WaterNot soluble in waterLess dense than water; Tend to float on the surfaceIf a small amount is poured on water, it forms a monolayer (one molecule thick) with the hydrophilic ends of the molecule orienting towards the water.*WaterAirPolar phosphate groupsNon-polar hydrocarbon chains

PhospholipidsIf shaken vigorously with water, they form a suspension of droplets called micelles. Hydrophilic ends of the molecule face outwards to interact with the water, while the fatty acid chains face inwards and tend to bind to each other.*WaterMicelles in water

Waxes

Formed by the condensation of many fatty acids with longer chain alcohols (longer than glycerol). Used mainly as a waterproofing material by plants and animals. E.g., cuticle, epidermis, skin, feather, human ear canal. Most waxes melt at higher temperatures than triglycerides and are solid at room temperature.*

SteroidsAll have a basic 4-ringed carbon rigid backboneDo not have fatty acids. Have no structural relationship to fats and phospholipidsClassified as lipids because they are insoluble in water and soluble in organic solvents. e.g., testosterone, oestrogen, cholesterol

*

Steroids - Cholesterol

One of the most common steroids Found in blood, nervous tissue and cell membranes. Found in a free state or in combination with fatty acids.*

Other functions of lipidsShock absorbers for internal organsCarries fat soluble vitamins (A,D,E,K)Accentuates the bodySupplies essential fatty acids

*

*********Stearic acid is useful as an ingredient in making candles, soaps, plastics, oil pastel, cosmetics and for softening rubber. Stearic acid is used to harden soaps, particularly those made with vegetable oil, that otherwise tend to be very soft *Linoleic acid is a polyunsaturated fatty acid used in the biosynthesis of prostaglandins and cell membranes and in other natural oils such as vegetable oil, especially sunflower oil.Linoleic acid is also used in making soaps, emulsifiers, and quick-drying oils. **hydrophobic because not polar since mostly C-H no O which is electronegative which confers polarity***************Choline and its metabolites are needed for 3 main physiological purposes: structural integrity and signaling roles for cell membranes, cholinergic neurotransmission (acetylcholine synthesis), and as a major source for methyl groups via its metabolite, trimethylglycine (betaine) that participates in the S-adenosylmethionine synthesis pathways.When choline is metabolized by the body, it may form trimethylamine, a compound with a fishy odor. Hence, when large amounts of choline are taken (such as 10-16 grams/day as a dietary supplement), the person may suffer from a fishy body odor. The foods richest in phosphatidylcholine -- the major delivery form of choline -- are beef liver, egg yolks and soy. Beef liver, iceberg lettuce, peanut butter, peanuts, sunflower seeds, and cauliflower are some foods that contain free choline.

Inositol, or cis-1,2,3,5-trans-4,6-cyclohexanehexol, is a cyclic polyalcohol that plays an important role as a second messenger in a cell, in the form of inositol phosphates. It is found in many foods, particularly in cereals with high bran content.It is classified as a member of the vitamin B complex, though it is not considered a vitamin per se, since the human body can synthesize it.

Serine, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the L-stereoisomer appears in mammalian protein. It is not essential to the human diet, since it can be synthesized in the body from other metabolites, including glycine. Serine was first obtained from silk protein, a particularly rich source, in 1865. Serine is important in metabolism in that it participates in the biosynthesis of purines and pyrimidines, cysteine, tryptophan (in bacteria), and a large number of other metabolites.

******