LIPIDS AND FATSLIPIDS AND FATS

• *A group of organic substances that are greasy to touch and insoluble to H2O but

• soluble in organics solvents/non-polar solvents such as ether, benzene, alcohol and choloroform.

• Contain C,H,O but compared to carbohydrates, have less O2 in proportion to C & H

• Basic structural unit: fatty acids• Are chemically composed of 5 main

elements: C, H,O, N, P.• Composed of about 5% of the organic

matter of the cell.

FATSFATS

• Simple lipids

• Most concentrated source of energy

• Composed of C, H and O but C is greater in number and ratio of H to O is higher

• Solid at room temperature

OILOIL

• Physical state of fats that is liquid at room temperature

• Example: Mineral and lubricating oil from petroleum or oil of cloves

TrigycerideTrigyceride

• Chemical and clinical names for fats and oils

• Ester of glycerol and fatty acids

• Form of fats found in foodstuff and fat depot of most animals

GlycerolGlycerol

• 3 carbon chain which makes up the core of fat molecules, such that 1 molecule of fatty acid is attached to each of the 3 carbon unit of glycerol

H - glycerine linkage

H C OH HOOC R(CH)

H C OH HOOC R(CH)

H C OH HOOC R(CH)

H

Glycerol Fatty Acid Simple Triglyceride Tristearin

• If R1R17 and R33 are different they are considered mixed triglyceride

• Example– R1 C17 H33 Oleic Acid

– R2 C17 H35 Stearic Acid

– R3 C15 H31 Palmitic Acid

Functions of LipidsFunctions of Lipids1. Source of Energy

Fat as the most concentrated source of energy 9 cal/g

As adipose tissue, it is the major source of energy stored in quantity by the body

Fat is converted to acetyl CoA which yields great mount of ATP

2. Source of Essential Fatty Acids– From seed oils of wheat germ, corn

soybean, walnut, cotton seeds3. Carrier of Fat soluble vitamins and their

precursor

4. Insulation• subcutaneous layer of fat reduces heat

loss in cold weather (helps maintain body temperature)

• Excessive heat layer or subcutaneous fats (obesity) interfere with heat loss during warm weather thereby increasing discomfort

5. Protection of Vital Body Organs• -especially from physical shock

6. Palatability– Responsible for flavors and aroma of

foods in the diet– It stimulates flow of digestive juices

7. Satiety value– Fats retard the emptying of the stomach

(reduce gastric motility) and stay longer therefore delays the onset of hunger which makes the individual feel satisfied for a longer period of time

8. Acts at emulsifying agentLecithin helps in transport of fatty substances that cannot easily pass through the cell membrane

9. Lubricants Which aid in elimination10. Precursor of Prostaglandins Participates in the regulation of blood

pressure, heart rate and lipolysis11. Body Composition Female 18-25% of BW

Male 15-20%

12. Important constituent of tissue/cell membrane structure (phospholipids, cholesterol) - 30-40% lipids; 60-7-% proteins; RBC – phosphoglycerides

13. protective form of cell walls of many bacteria; leaves of higher plants; or the exoskeleton of insects and the skin of the vertebrates;

in animals, the waxes keep feathers, skin and hair soft, pliable and H2O repellant. While the cuticle waxes of plants protect them both from dehydration and from invasion of harmful organisms

14. As enzyme cofactors ( some fat soluble vitamins).

15. As transport form of some neurotransmitters ex. Acetylcholine

16. As receptors in nerve ending membranes.

17. As determinants of immunological specificity

Fatty AcidsFatty Acids

• Consist of a chain series of Carbon attached to a carboxyl group which concerns the acidic property of the compound

• They give a diversity and chemical specificity to the natural fats, similar to that given to proteins by amino acids

Classification of LipidsClassification of LipidsI. Classification by White – based on the

presence or absence of glycerol.

1. Fatty Acids

2. Lipids containing glycerol

a. Neutral fats (triacylglycerols)

b. Phosphoglycerides

c. Cardiolipin

d. Plasmologens

3. Lipids not containing glycerol a. Sphingolipids b. Aliphatic alcohol and waxes c. Terpenes 2 major grps of d. Steroids non-saponifiable lipids e. Prostaglandins 4. Lipids combined with other classes of

compounds a. Lipoproteins and proteolipids b. Glycolipids

II. Classification by Bloors:A. Simple Lipids- ester of fatty acids or other

alcohol

1. neutral fats or trigyceride 3 fatty acids combined with glyceride 2 fatty acids + glycerol + diglyceride 1 fatty acid + glycerol + monoglyceride– simple fats- all fatty acids are the same – Mixed fats- at least 2 fatty acids are

different

2. Waxes-at least 2 fatty acids with an alcohol other than glycerol

- long chain or cyclic alcohol - they are not digested by fat

splitting enzyme, so no nutritional value

- includes esters of cholesterol, Vitamin A and D

B. Compound Lipids- esters of fatty acid containing

groups in addition to an alcohol and fatty acid (CHO phosphate or nitrogenous group)

1. Phospholipids- fats containing H3PO4 and a

nitrogenous base in addition to fatty acid and glycerol

- plays an important role in the transport of fat to the different tissues and appear to be involved in its utilization

– Lecithin- emulsifying agent

– Cephalin- thromboplastic substance which initiates blood coagulation

2. Glycolipids- contains carbohydrate and nitrogenous

base

example: Cerebrosides which contain a molecule of glucose or galactose

3. Aminolipids or lipoproteins

- lipid molecule bound to protein; facilitate transport in the aqueous medium of blood

C. Derived Lipids- derivatives of simple and compound lipids due to

hydrolysis. - Some contain N or P or both, other contain S1. Fatty Acids2. Glycerol3. Steroids

1. Sterols- cholesterol2. Bile Acids- glycocholic acid3. Sex Hormones- progesterone4. Adrenal corticosterol5. Vitamin D

1. ergocalciferol (D1)

2. Cholicalceferol (D3)

FATTY ACIDSFATTY ACIDS• Content of fats and oils which are the

basis of their physical and chemical properties

• The most abundant occurring lipids• The building blocks of several classes

of lipids and neutral fats, phosphoglycerides, glycolipids, cholesterol esters and some waxes

• Products of fat hydrolysis

A. Structure of Fatty acidsA. Structure of Fatty acids

1.They are mainly straight chain aliphatic, monocarboxylic acids, ranging in chain lengths from 4 to 24 C atoms.

2.Type formula

( hydrophobic – R – COOH – hydrophilic)

3. FA maybe saturated and unsaturated

4. Most naturally occurring fatty acids are even numbered containing 16 to 18 C atoms.

5. Double bonds in naturally occurring fatty acids are always in a cis – as opposed to trans – configuration

a. the presence of the double bond gives rise to the possibility of geometric isomerism

b. the double bond forms around which the rest of the molecules maybe oriented; if the radicals are on the same side of the bond, the compound is called a cis – form; if on opposite sides, a trans – form.

HOOH(CH2)7CH CH(CH2)7COOH CH3(CH2)7CH CH3(CH2)7CHcis-oleic acid trans-elaidic acidCH3 H CH3 H

C C C C H H COO

COO

Classification of Fatty AcidsClassification of Fatty Acids1. Essential or indispensable Fatty Acids

When the body cannot synthesize them from other substance, it must be provided in the diet

Examples:• Linoleic Acid- (n-6 PUFA) sole dietary• Linolenic Acid- (n-3 PUFA) promotes growth• Arachidonic Acid- promotes growth

Deficiency in the diet produces:

1. Impairment of growth

2. Some form of dermatitis

3. Excessive thirst

4. Kidney damage in advance cases

5. Some cases of eczema and dermatosis- caused by vit. A deficiency are cured by addition of indispensable FA

2. Unsaturated Fatty Acids- if f.a. contains 1 double bond

monounsaturated, (oleic)- if f. a. contains 2 or more double bonds

polyunsaturated, (linoleic a., linolenic a., arachidonic a.)

• Unstable and reactive due to the presence of (=) bonds.

• Ends in “enoic”

Most important unsaturated fatty Most important unsaturated fatty acids:acids:

1. Oleic acid (C18H34COOH) – olive oil

CH3 (CH2)7 CH = CH (CH2)7 COOH

2. Linoleic acid (C18H32COOH) – corn oil

CH3 (CH2 )4 CH = CHCH2CH

= CH (CH2)7 COOH

3. Linolenic acid (C18H30COOH) – linseed oil

CH3CH2CH = CHCH2CH = CHCH2CH

= CHCH (CH2)7 COOH

Importance of Unsaturated FAcidsImportance of Unsaturated FAcids

1. Maintains normal growth and reproduction of lower animals

2. Prevents eczematous lesions of skin in man

3. Lowers the serum cholesterol level in man (polyunsaturated type)

3. Saturated Fatty Acids3. Saturated Fatty Acids• Fatty acids wherein the C atom holds as many H as it can hold.• Found in animal and vegetable fats (coconut and peanut oil)

H H

C C with w hydrogen atoms attached to each C atom

H H

eg,. Stearic Acid, Palmitic acid, myristic acid

• Contains up to 8C atoms; belong to acetic acid series w/ general formula of CnH2nO2

• Saturated fatty acids has no double bonds• Systematic name ends in “anoic”

ex. Lauric or duodecanoic – C12

myristic or tetradecanoic – C14

palmitic or hexadecanoic – C16

stearic or octadecanoic – C18

Classificattion of SFA accdg to the no. of C atoms:

1. Short chain – w/ < 6 C atoms

ex. Butanoic – 4 C atoms; pentanoic – 5 C

2. Medium chain – w/ 6-10 C atoms

ex. Heptanoic, octanoic, nonanoic, decanoic

3. Long chain – w/ H and more C atoms

ex. Dodecanoic, octadecanoic

Nomenclature of Fatty acidsNomenclature of Fatty acids1. Delta ( ) system – C atoms are numbered beginning

from the carboxylic end (COOH) ex. Linoleic acid - 18: 2c 9, 12 COOH CH3 2. N system (Number system) counting starts from the

methyl end of the molecule ex. Linoleic acid – 18: 2n – 6, 93. Omega system

Some metabolically important FA:Some metabolically important FA:Common name Systematic

nameNo. of C atoms

No. of = bonds

Chemical formula Occurrence

Lauric duodecanoic 12 0 C12H24O2 Laurel,

coconut

oil

Myristic tetradecanoic 14 0 C14H28O2 Coconut,nutmeg

Palmitic hexadecanoic 16 0 C16H32O2 Plants & animal fats

Stearic octadecanoic 18 0 C18H36O2 Animal fats

Palmitoleic Cis 9 hexadecanoic

16 1 C16H30O2 Butter, fish, oils,

hen fat

Oleic Cis 9 octadecanoic

18 1 C18H34O2 Cottonseed oil

Linoleic Cis 9 octadecadienoic

18 2 C18H32O2 Linseed oil

Linolenic All-cis-9,12,15 octadecatrienoic

18 3 C18H30O2 Linseed oil

Arachidonic All cis - 5,8,11,14 eicosatetraenoic

20 4 C20H32O2 Lecithin, cephalin, liver,

fish

Physical properties of Fatty acids:Physical properties of Fatty acids:1. Odorless, tasteless,colorless, greasy to

touch2. Insoluble to water but are soluble in

organic solvents such as chloroform, methanol, ether or benzene, carbon tetrachloride

3. Only small amounts are present in nature; abundant in amide or ester linkage

4. Boiling point and melting point rise w/ inc in chain length;inc. C atoms – inc. melting point – less soluble

5. At physiological ph, fatty acids are ionized and possess amphipathic character ( their hydrocarbon tail is hydrophobic while the carboxylic head (COOH) is hydrophilic.

6. Solubility decreases (inversely proportional) w/ increasing chain length. FA w/ R groups higher than C6 are only slightly soluble in water.

7. Specific gravity of fats is less than 0.

Chemical properties of FA due to Chemical properties of FA due to double bonds:double bonds:

1. Hydogenation- addition of hydrogen; hardening – UFA – hydrogenated by gaseous hydrogen in the presence of catalyst like platinum, palladium or nickel

* principle involved in the manufacture of artificial butter (oleomargarine) from vegetable oils.

2. Halogenation – Br and I

3. Oxidation leading to rancidity

exposure to air – acidic UFA – due to hydrolysis – liberation of volatile FA – formation of peroxides,odoriferous volatile aldehyde, ketones and acids – rancid odor

Lipoxidase – enzyme causing rancidity of fats and oils at room temperature

- change maybe catalyzed by bacteria

Types of rancidity

1. Hydrolytic rancidity – bad odor and taste are due to the free FA liberated (hydrolysis)

ex. Butterfat – w/ high %age of volatile FA

2. Oxidative rancidity – caused by oxidation of UFA and their = bonds w/ the production of shortered chain acids, aldehydes and ketones;more impt. type

ex. Tallowy butter – dairy industry

* O2 is necessary for oxidative rancidity. Light, heat, moisture and traces of certain metals such as Cu hasten the oxidative process

Due to COOH (carboxylic acid)Due to COOH (carboxylic acid)1. Esterification – a very slow reaction but maybe

accelerated by heat or addition of hydrogen ion2. Saponification – metallic salts of fatty acids

(soaps) will be produced when treated w/ alkali. - Na & K salts are soluble in water Na salts – hard soaps K salts – soft soaps - Ca & Mg salts and the heavy metals such as

Pb & Zn are insoluble in water3. Hydrolysis – fats are hydrolyzed by dilute acids

to FA and glycerol

• Assignment: ( Watch LORENZO’S OIL FILM )• 1. What ails the main character in the story? What are

the symptoms presented?• 2. What are the preventive measures/cure given to

remedy the problem?• 3. Is there a real cure to Lorenzo’s disease/illness?• 4. What is the mixture of Lorenzo’s oil?• 5. How will you relate the subject Biochemistry in the

story? • Write your answers in a one whole intermediate pad

paper. Submission is on Friday.• We’ll have discussion of Lipids and about the film.