Lipids Flashcards
heterogenous group of compounds. They are compounds of long chain fatty acids and glycerol and higher monohydric alcohols.
Lipids
triglycerides (or currently referred to as triacylglycerols) because they are esters composed of three fatty acid units joined to glycerol, a trihydroxy alcohol.
Fats and oils
Functions of fats
They provide energy for living organisms, insulate body organs, and transport fat-soluble vitamins through the blood.
acylglycerols are solid generally if the fatty acids are saturated and liquid when unsaturated .
True
What do you do when both solid and liquid is present in an acylglycerol
both are present, cooling results in the deposition of the saturated portion e.g. stearin in cod liver oil.
all three OH groups on the glycerol molecule are esterified with the same fatty acid, the resulting ester is…..
simple triacylglycerol.
If they are different esterification it will be called “mixed triacglycerol”
The unsaturated acids is mostly linked to the secondary hydroxyl esp C18 olefinic acids
True/false
True
Triacylglycerides obtained from animals are fats, those obtained from plants are….?
Oils
What is the most abundant saturated fatty acid and what is the most abundant unsaturated
Palmitic avid - saturated
Oleic acid- unsaturated
May be applied to natural mixtures containing appreciable quantities of esters derived from higher monohydric alcohols of the methyl alcohol series combined with fatty acids.
Waxes
Egs. dodecyl alcohol , (C12H25OH), ceryl alcohol (C26H53OH) and myricyl alcohol (C30H61OH).
Sources
carnauba wax from plants and animal products include: spermaceti, beeswax and wool-fat.
What makes waxes different from fats
Waxes differ from fats by being saponified only by alcoholic alkali whereas fats are saponified by both aqueous and alcoholic alkali. Waxes also contain a considerable amount of free acids.
Esters of glycerophosphoric acids in which the 2 free hydroxyls of the glycerol are esterified with fatty acids and the 2 of the phosphoric acid is esterified to an alcohol (choline, serine glycerol etc
Lecithins
Where are lecithin found in animals
complex lipids in active tissues of the brain and liver.
Ways fats and oils are obtained from plants
American cotton seeds by delinting and castor or ground nut are decorticated .
•The oil may be obtained by cold or hot expression, centrifuging or solvent extraction. The crude oil may be refined for commercial use e.g. olive oil .
Why does castor oil require steaming in its extraction
inactivate lipase but also to detoxify toxin -ricin
acids which combine with glycerol in the naturally occurring fats and oils. These acids contain even number of carbon atoms linked together in long chains which are in general un-branched.
Fatty acids
Classification of fatty acids
a. Saturated fatty acids
•b. Unsaturated fatty acids
•c. Branched chain fatty acids, and
•d. Cyclic fatty acids.
What are saturated fatty acids and examples
contain only single bonds in their hydrocarbon chain.
•The general formula is:
–R — COOH
Most occurring fatty acids are palmitic(C16) and stratum acid (C18)
What characterizes unsaturated fatty acids
-one or more d-bonds
Cistrans isomer
Oleic acid (C10), Ricinoleic (C18) Linoleic acids
Examples of unsaturated fatty acids
Which type of unsaturated acid are considered beneficial to humans
Monounsaturated fatty acids
important dietary fats.
•They lower disease risk and found in foods such as: vegetable oils (such as olive, sunflower, soy, and corn), nuts, seeds, and fish
Omega-3, omega-6 and omega-9 fatty acids
What does the “omega 3 “ refer to
refers to the position of the final double bond which is three carbon atoms from the “omega” or tail end of the molecular chain.
Benefits of omega 3
Hearth health
Etc etc
What is the most common omega-6 fat
Linoleic acid which can be converted into longer omega-6 fats such as arachidonic acid (ARA).
an omega-6 fatty acid found in certain oils, such as evening primrose oil and borage oil.
Gamma linolenic acid (GLA)
What is the function of GLA
When consumed, it is converted to another fatty acid, dihomo-gamma-linolenic acid (DGLA). When used in a high dose as GLA supplements they reduced symptoms of rheumatoid arthritis.
Which Omega is monosaturated and which is poly saturated
Mono- Omega 9
Poly-omega 3
Example of Omega 9
Oleochemicals acid and most monosaturates
Health benefits of Omega 9
high-monounsaturated fat diets could reduce plasma triglycerides by 19% and “bad” very-low-density-lipoprotein (VLDL) cholesterol by 22% in patients.
mlkm
straight-chain polyunsaturated fatty acids (PUFAs) of 20 carbon units in length that have been metabolized or otherwise converted to oxygen-containing products.
Eicosanoids
As chain length and degree of saturation of solvent increases, what happens to solubility of fats
It decreases
Saturated and unsaturated which is solid at room temperature
Saturated fatty acids are solid at room temperature, while unsaturated fatty acids are liquid.
What causes the yellow color of butter since fats and oils are colourless
The yellow colour of butter is due to carotene pigment; the taste of butter comes from two compounds—diacetyl and 3-hydroxy-2-butanone—produced by bacteria in the ripening cream from which the butter is made.
What reduces the melting points of fatty acids
Short chain or unsaturation( since they are liquids)
What increases viscosity and what decreases it
Increasing the degree of unsaturation, the viscosity decreases and when the length of the chain increases the fatty acids components also increases the viscosity.
What increases refractive index
Increasing the degree of unsaturation and length of chain
What happens when fats are treated with mineral acids, the alkalis or fat enzyme lipase or hydrolases
Hydrolysis which yields glycerol and fatty acid constituents
Hydrolysis by alkalis, such as NaOH or KOH leads to the formation ….
sodium or potassium salts of fatty acids. The salts are known as soaps and process of its formation is saponification.
Between KOH and NaOh what makes soap soft or hard
KOH makes soft soap while NaOH makes hard soap.
What are rancid oils or fats
Oils and fats on long storage in contact with heat, light, air and moisture
What chemical changes result in rancididty
i) Enzymatic hydrolysis,
•(ii) Air oxidation of unsaturated fatty acids, and
•(iii) β- oxidation of saturated fatty acids.
–Hydrolysis of fats is caused by enzyme lipase which is produced by microorganisms present
What enzyme causes hydrolysis if fat to rancid
Lipase
How can oils be converted into solid fats (glycerides of saturated fatty acids)
Oils containing unsaturated fatty acids can be hydrogenated in presence of high temperature, pressure and finely divided nickel.
What happens when excess of hydrogen is passed through oils under pressure and in presence of copper-chromium catalyst
And what is hydrogenolysis
Oils and fats are converted into glycerol and a long chain aliphatic alcohol
The splitting of fat by hydrogen is known as hydrogenolysis.
What happens when unsaturated fat is treated with halogens like iodine
they take up iodine or other halogens at their double bond site.
What is iodine number of fats
Iodine number is the mass of iodine in gm that is consumed by 100 gm of the fat or wax. They are often used to determine the amount of unsaturation in fats, oils and waxes.
What is acid value and formula
The acid value is the number of mg of potassium hydroxide required to neutralize the free acid in 1 g of the substance.
= acid x 5.61/ weight of substance
Sap value formula
Sap value = (b-a)x factor of acidx 28.05/ weight
What is sap value used to measure
measure of the average molecular weight (or chain length) of all the fatty acids present
Why do long chain acids have low sap value to short chain
because they have a relatively fewer number of carboxylic functional groups per unit mass of the fat as compared to short chain fatty acids
What is ester value
the difference between the saponification value and acid value gives the ester value:
Why do micelles(oil droplets) repel each other
because of their charged surfaces and do not coalesce
substances frequently found dissolved in fats and oils which cannot be saponified by the caustic alkalis but are soluble in the ordinary fat solvents and are extractable into ether.
Unsaponifiable matter
Examples of unsaponifiable matter
higher aliphatic alcohols, sterols, pigments, and hydrocarbons.
What is hydroxyl value
the number of milligrams of potassium hydroxide required to neutralize the acetic acid
measure of the content of free hydroxyl groups in a chemical substance,
an oil that hardens to a tough, solid film on exposure to air. The oil hardens through a chemical reaction in which the components polymerize by the action of oxygen.
Drying oil
What is the iodine number an oil should have before it becomes drying oil
> 130
What are drying oils used for
They are a key component of oil paint and some varnishes. Some examples include: linseed oil, tung oil , walnut, poppy seedy
What is a semi drying oil
A semi-drying oil is one which partially hardens when it is exposed to air. This oil has an iodine number of 115-130. Corn oil, Cottonseed oil, Sesame oil and Grape seed oil.
Examples of non drying oil
Almond Cocoa butter Coconut oil Mineral oil Olive oil Peanut oil
What is acrolein test
Aim:to detect fat or glycerol
Reagent: potassium bisulphate (KHSO4)
+ test: glycerol portion of the molecule is dehydrated to form an unsaturated aldehyde, acrolein that has a pungent irritating odour
highly toxic fats that can cause insulin resistance, inflammation and significantly raise the risk of serious diseases like heart disease.
Trans fats
It is formed transiently as intermediates in the biosynthesis of glycerophospholipids.
Diacylglycerols
What is iodine value
High iodine value in unsaturated fats mean?
iodine adsorption value or iodine number or iodine index) is the mass of iodine in grams that is consumed by 100 grams of a chemical substance.
higher the iodine number, the more C=C bonds are present in the fat. Or high unsaturation
Family if arachis oil and use
Leguminosae
laxative and given as an enema. May be used to adulterate other fixed oils e.g. olive oil
Elaeis guineensis OG the family (Arecaceae).
Palm kernel oil
What makes palm kernel different from palm oil
It differs chemically from palm oil in containing a high proportion (50%) of the triglycerides of lauric acid, a saturated, medium chain length fatty acid .
What is Fractionated Palm Kernel Oil BP
palm oil which has undergone selective solvent fractionation and hydrogenation. It is a white, brittle solid, odourless or almost so, with m.p. 31–36°C making it suitable for use as a suppository base.
Which oil has antibiotic resistant to Staph. aureus strains
Linseed oil
Why is lalonin not a true fat
lanolin lacks glycerides (glycerol esters), it is not a true fat. Lanolin primarily consists of sterol esters.
