Introduction to Lipids, Lecture notes of Biochemistry

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BIOCHEMISTRY 1

ND

CLASS

UNIVERSITY OF ANBAR COLLOGE OF SCIENCE BIOLOGY DEPARTMENT

Lipids Lecture one( 1 ) Hameed Hussein Ali Chemistry Department College of Science

Lipids

Classification of Lipids:- Lipids are divided into three categories: 1 - Simple lipids: are esters of fatty acids with glycerol A-Neutral fats B-Oils C-Waxes 2 - compound lipids: are esters of fatty acids with alcohol binding with other type of compounds. Like phospholipids, lipoproteins, glycolipids. 3 - Derived lipids: are compounds produced when simple or compound lipids undergo hydrolysis. Derived lipids include such substances as fatty acids,glycerol,other alcohols,sterols(solid alcohol having a high molecular weight), fatty aldehydes and ketone bodies

1 - Simple lipid:- Fatty acid:- The principle component in most lipids – FA are straight chained ontains 4 - 30 of C atoms as carboxylic acid which FA are carboxylic acid with straight chain of hydrocarbon residue either saturated or unsaturated contain 4 - 30 of carbon atoms.

B- Unsaturated fatty acids:-

Active carboxylic fatty acids because they

are containing one or more double bond;

therefore they are liquid in room

temperature.

Example:

Stearic acid C

Oleic acid C

Linoleic acid C

Linolenic acid C

C

H

COOH

C

H

COOH

C

H

COOH

C

H

COOH

Saturated

Structural lipid They are esters of fatty acids with glycerol Fatty acid + glycerol ester Simple glyceride H 2 C-O-C-C 17 H 35 H-C-O-C-C 17 H 35 H 2 C-O-C-C 17 H 35 Tristearrin

O

O

O

H 2 C-O-C-C 15 H 31 HC-O-C-C17H H 2 C-O-C-C 15 H 31 Mixed glyceride 2-Stearo-1,3-di Palmitin

O

O

O

Chemical react:- Hydrolysis :- when fats are treated with enzymes acids,or bases, they hydrolyze to form fatty acids and glycerol. Example: **H 2 C O HC H 2 C C O O O C C 15 H 31 C C 15 H 31 O O C 15 H 31 3H 2 O 3 C 15 H 31 COOH 2HC OH HC H 2 C OH OH

glycerol**

Saponification:- Is the heating of a fat with a strong base such as NaOH to produce glycerol and the salt of fatty acid

H 2 C O

HC

H 2 C

C

O

O

O

C

C 17 H 35

C

C 17 H 35

O

O

C 17 H 35

3 NaOH C 17 H 35 C

O

ONa

H 2 C OH

HC

H 2 C

OH

OH

glycerol

Soduim Stearate

(soap)

tristearin

The sodium or potassium salt of a fatty acid is called a soap. Example:

[Acrolein test] :- It’s a test for the presence of glycerol. It is sometimes used as a test for fats and oils, since all fats and oils contain glycerol. When glycerol is heated to a high temp. especially in the presence of adehydrating agent such as KHSO 4 , an aldehyde acrolein results. CH 2 -OH CH-OH CH 2 -OH heat KHSO 4 H-C=O H-C CH 2 +^ 2H 2 O acroline

Waxes:- Compounds produced by the reaction of a fatty acid with a high molecular weight monohydroxylic alcohol. C> 15 Waxes are insoluble in water, non reactive and flexible, hence waxes make excellent protective coatings. Example: myricyl palmitate CH 3 -(CH 2 ) 14 -C-O-CH 2 -(CH 2 ) 28 -CH 3 O

a- phosphoglycerides:- A structure of a phosphoglyceride can be represented as: At C 1 and C 2 of glycerol there are esters of F.A. At C 3 there is a phosphate group (phosphatidic acid). Phosphate group can be bonded to a nitrogen compound. Like : choline, ethanolamin and serine. G l y c e r o l F-A FA

P

H 2 C - O - C - R 1

O

H C - O - C - R 2

O O

H 2 C - O - P - O H

O H

P h o sp h a tid i c a cid

• If phosphatidic acid bonded with choline the product compound called : phosphatidyl choline (Lecithine) R 2

- C - O - C H

O

C H

2

- O - C - R

1

O

C H

2

- O - P - O - C H

2

- C H

2

- N H

+ ( C H 3

3 O

O

C h o l i n e

* If phosphatidic acid bonded

with serine the product

compound is called

phosphatidyl serine

R 2 -C-O-CH

CH 2 -O-C-R 1

CH 2 -O-P-O-CH 2 -C-NH 3

O O H COO O

B-Phosphosphingosides :- called sphingolipids differ from phophoglycerides in that they contain the alcohol sphingosine in place of glycerol. One particular type of sphingolipid called sphingomylein is present in large amount in brain and nerve tissue. The general formula for a shingolipid is Choline F.A. Sphingosine phosphoric acid