Lipids

Lipids Made up of C, H and O Can exist as fats, oils and waxes They are insoluble in water They are a good source of energy

(9 k cal / g) They are poor conductors of heat Most fats & oils are triglycerides

Lipids Biomolecules that contain fatty acids or a steroid

nucleus. Soluble in organic solvents, but not in water. Named for the Greek word lipos, which means

“fat.” Extracted from cells using organic solvents.

Triglycerides Formed by esterification (condensation reaction

between 3 fatty acids and glycerol)

Glycerol

H

C

H C

C

H

H

H

H

O

O

O

H

H

Fatty acids Carboxyl group (-COOH) attached to a long non-polar hydrocarbon

chain (hydrophobic)

H

H

C

H

H

C

H

H

C

HC

O

O

H

C

HH

C

H

H

C

H

H

C

H

H

A saturated fatty acid (no double bonds)

A polyunsaturated fatty acid

C

O

O

H

C

HH

C

H

H

C

H

H

C

H

C

H

H

C

H

H

C

H

H

A monounsaturated fatty acid

HH

C

O

O

H

C

HH

C C

C C H

C

H

H

C

H

HH H

Esterification

C

O

O

H

C

HH

C

H

H

C

H

H

C

H

H

Glycerol Fatty acid

H

C

H C

C

H

H

H

H

O

O

O

H

H

Esterification

C

O

O

H

C

HH

C

H

H

C

H

H

C

H

H

Glycerol Fatty acid

H

C

H C

C

H

H

H

H

O

O

O

H

H

Esterification

C

OH

C

HH

C

H

H

C

H

H

C

H

Glycerol Fatty acid

C

H C

C

H

H

H

H

O

O

O

H

H

HO

H

Esterification

C

OH

C

HH

C

H

H

C

H

H

C

H

C

H C

C

H

H

H

H

O

O

O

H

H

HO

H

Ester bond

water

This happens three times to form a triglyceride

glycerol fatty acids

Esterification

Phospholipids

One fatty acid can be replaced by a polar phosphate group

glycerol Hydrophobic fatty acids

hydrophilicphosphate

Classification of Lipids Simple lipids Compound lipids (Complex) Derived lipids

Simple lipids

The alcohol is glycerol

Oil (liquid at room temperature)

Fat (solid at room temperature)

Natural lipids need 3 F.As. and one molecule of

glycerol to form triglycerides + 3 H2O

A) Natural Lipids

Simple lipids

Most natural waxes are esters derived from a fatty

acid and a long-chain alcohol

Main biological function of waxes: water barrier

Bee waxes are formed by honey bee and formed

from merioyl alcohol and palmitic acid.

B) Waxes

Waxes Most natural waxes are esters derived from a fatty acid

and a long-chain alcohol

• Main biological function of waxes: water barrier

Myricyl cerotatePresent in beeswax

Cerotic acidA fatty acid

remove H2O

LeavesWax minimizes water evaporation

Myricyl alcoholLong chain alcohol

FeathersWax minimizes wetting

Compound lipids

F.A + alcohol + other group Phospholipids (contain phosphate group) Glycolipids (contain carbohydrates) Lipoproteins (contain proteins)

Derived lipids

Hormones Steroids

Non-polar lipids (fats) are the principal molecules for energy storage.

Polar lipids (nitrogen and phosphorus containing) are components of biological membranes.

The steroid (class of lipids) (cholesterol) is found in biological membranes and used as a precursor for many hormones, bile and vitamin D

Miscellaneous lipids present only in minor quantities in the cell are involved as light-absorbing pigments (β-carotene, retinal), enzyme cofactors (vitamin K), signal molecules (prostaglandins), and electron carries.

Diversity in structure leads to a diversity in biological function

Diversity in structure leads to a diversity in biological function

Used as a fuel reserve (when needed)

Provide body with essential fatty acids

Fats under skin (subcutaneous) are used as insulator and protecting and maintaining the body temperature.

Fats provide the protection and fixation of internal organs.

Lipoproteins enter in the formation of cell wall, muscles, mitochondria and microsomes.