LIPID: STRUKTUR DAN FUNGSI

Lipid

• Def: compounds which are relatively insoluble in water, but freely soluble in non polar organic solvents like benzene, ether, chloforom etc.

Function

1. Storage form of energy2. Structure component of biomembranes3. Insolution4. Shape and contour of body5. Protect internal organ6. Metabolic regulator7. Electric insulator in neurons8. Help in absorbtion of fat soluble vitamins9. Taste and palatability

Clinical importance of lipid

• Obesity• Artheroscreloris• Fatty liver• Lipid storage disorder• Lipoproteinimias

CLASSIFICATION OF LIPIDS

• Simple Lipids, exp: fat or oil, wax• Compound Lipid

– Phospholipid – lechitin– Glycolipids – cerebrosides– Sulpholipids – sulfated cerebrosides

• Derived lipids – exp. Fatty acids, prostaglandin, steroids, etc.

• Micellaneous lipids, exp. Carotenoids, squalene, etc.

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Types of Lipids

• Lipids with fatty acidsWaxesFats and oils (trigycerides)PhospholipidsSphingolipids

• Lipids without fatty acidsSteroids

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Fatty Acids

• Long-chain carboxylic acids• Insoluble in water• Typically 12-18 carbon atoms (even number)• Some contain double bonds

corn oil contains 86% unsaturated fatty acids and

14% saturated fatty acids

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Saturated and Unsaturated Fatty Acids

Saturated = C–C bondsUnsaturated = one or more C=C bonds

COOH

COOH

palmitoleic acid, an unsaturated fatty acid

palmitic acid, a saturated acid

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Structures

Saturated fatty acids• Fit closely in regular pattern

Unsaturated fatty acids• Cis double bonds

COOHCOOHCOOH

C CH H

COOHcis double bond

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Properties of SaturatedFatty Acids

• Contain only single C–C bonds

• Closely packed

• Strong attractions between chains

• High melting points

• Solids at room temperature

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Properties of UnsaturatedFatty Acids

• Contain one or more double C=C bonds• Nonlinear chains do not allow molecules to pack

closely• Few interactions between chains• Low melting points• Liquids at room temperature

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Learning Check L1

How would the melting point of stearic acid compare to the melting points of oleic acid and linoleic acid? Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain.

stearic acid (18 C) saturatedoleic acid (18 C) one double bondlinoleic acid (18 C) two double bonds

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Solution L1

Stearic acid is saturated and would have a higher melting point than the unsaturated fatty acids. Because linoleic has two double bonds, it would have a lower mp than oleic acid, which has one double bond.

stearic acid mp 69°Coleic acid mp 13°Clinoleic acid mp -17°C

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Fats and Oils

Formed from glycerol and fatty acids

+

HO C (CH2)14CH3

O

HO C (CH2)14CH3

O

HO C (CH2)14CH3

O

glycerol palmitic acid (a fatty acid)

CH

CH2 OH

OH

CH2 OH

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Triglycerides (triacylglcerols)

Esters of glycerol and fatty acids

CH

CH2

CH2 O

O

O

C (CH2)14CH3

O

C (CH2)14CH3

O

C (CH2)14CH3

O

ester bonds

+

+

+

H2O

H2O

H2O

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Learning Check L2

What are the fatty acids in the following triglyceride?

CH

CH2

CH2 O

O

O

C (CH2)16CH3

O

C

O

(CH2)7CH CH(CH2)7CH3

C

O

(CH2)12CH3

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Solutions L2

What are the fatty acids in the following triglyceride?

CH

CH2

CH2 O

O

O

C (CH2)16CH3

O

C

O

(CH2)7CH CH(CH2)7CH3

C

O

(CH2)12CH3

Stearic acid

Oleic acid

Myristic acid

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Properties of Triglycerides

Hydrogenation• Unsaturated compounds react with H2 • Ni or Pt catalyst• C=C bonds C–C bonds

Hydrolysis• Split by water and acid or enzyme catalyst• Produce glycerol and 3 fatty acids

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Hydrogenation

CH

CH2

CH2 O

O

O

C

O

(CH2)5CH CH(CH2)7CH3

C

O

(CH2)5CH CH(CH2)7CH3

C

O

+

(CH2)5CH CH(CH2)7CH3

H23Ni

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Product of Hydrogenation

Hydrogenation converts double bonds in oils to single bonds. The solid products are used to make margarine and other hydrogenated items.

CH

CH2

CH2 O

O

O

C (CH2)14CH3

O

C (CH2)14CH3

O

C (CH2)14CH3

O

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Hydrolysis

Triglycerides split into glycerol and three fatty acids (H+ or enzyme catalyst)

CH

CH2

CH2 O

O

O

C (CH2)14CH3

O

C (CH2)14CH3

O

C (CH2)14CH3

O H2O+3

3+ HO C (CH2)14CH3

O

CH

CH2 OH

OH

CH2 OH

H+

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Saponification and Soap

• Hydrolysis with a strong base• Triglycerides split into glycerol and the salts of fatty

acids • The salts of fatty acids are “soaps”• KOH gives softer soaps

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Saponification

3+ Na+ -O C (CH2)14CH3

O

CH

CH2 OH

OH

CH2 OH

CH

CH2

CH2 O

O

O

C (CH2)16CH3

O

C

O

(CH2)16CH3

(CH2)16CH3C

O

+ 3 NaOH

salts of fatty acids (soaps)

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Learning Check L3

What are the products obtained from the complete hydrogenation of glyceryl trioleate?

(1) Glycerol and 3 oleic acids(2) Glyceryltristearate(3) Glycerol and 3 stearic acids

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Solution L3

What are the products obtained from the complete hydrogenation of glyceryl trioleate?

2. Glyceryltristearate