CARBOHYDRATES & LIPIDS

CARBOHYDRATES



CARBOHYDRATES ARE ALDEHYDE OR KETONE DERIVATIVES OF

POLYHYDRIC ALCOHOLS ;CLASSIFIED

AS MONO,DI,OLIGO &POLY.

1.Monosaccharides

The monosaccharide commonly found in humans are classified according to the number of carbons they contain in their backbone structures

.

Classifications ALDOSES KETOSES Trioses (C 3 H 6 O 3 ) Tetroses (C 4 H 8 O 4 ) Glycerose (glyceraldehyde) Erythrose Dihydroxy acetone Erythrulose Pentoses (C 5 H 10 O 5 ) Hexoses (C 6 H 12 O 6 ) Heptoses (C 7 H 14 O 7 ) Ribose Glucose — Ribulose Fructose Sedoheptulose

GLUCOSE

Straight chain Haworth projection

Hemiacetal;reaction between aldehyde and hydroxy grp.

chair

Epimers:

 Isomers differing as a result of variations in configuration of the —OH and —H on carbon atoms 2, 3, and 4 of glucose are known as epimers.  4 th is Galactose , glucose , 2 nd mannose.

Pentoses of Physiologic Importance.

Sugar Source D D D -Ribose -Ribulose Arabinose D -Xylose Nucleic acids and metabolic intermediate Metabolic intermediate Plant gums Biochemical and Clinical Importance Structural component of nucleic acids and coenzymes, including ATP, NAD(P), and flavin coenzymes Intermediate in the pentose phosphate pathway Constituent of glycoproteins Constituent of glycoproteins L -Xylulose Plant gums, proteoglycans, glycosaminoglycans Metabolic intermediate Excreted in the urine in essential pentosuria

Sugar Source Hexoses of Physiologic Importance.

Biochemical Importance Clinical Significance D D -Fructose D Galactose D -Glucose Mannose Fruit juices, hydrolysis of starch, cane or beet sugar, maltose and lactose Fruit juices, honey, hydrolysis of cane or beet sugar and inulin, enzymic isomerization of glucosesyrups for food manufacture Hydrolysis of lactose Hydrolysis of plant mannan gums The main metabolic fuel for tissues; "blood sugar" Readily metabolized either via glucoseor directly Excreted in the urine (glucosuria) in poorly controlled diabetes mellitus as a result of hyperglycemia Hereditary fructose intolerance leads to fructose accumulation and hypoglycemia Readily metabolized to glucose; synthesized in the mammary gland for synthesis of lactose in milk. A constituent of glycolipids and glycoproteins Constituent of glycoproteins Hereditary galactosemia as a result of failure to metabolize galactose leads to cataracts

Glycosides

 formed by condensation between the hydroxyl group of the anomeric carbon of a monosaccharide, and a second compound that may or may not (in the case of an aglycone) be another monosaccharide.  aglycone (methanol, glycerol, sterol, phenol, N base;amine-N-glycosidic bond)  

Important glycosides

cardiac glycosides( contain steroids as the aglycone) derivatives of digitalis and strophanthus such as ouabain 

Streptomycin



Phlorhizin

Sugar Isomaltose Maltose Lactose Lactulose Sucrose Trehalose Source DISACCHARIDES Clinical Significance Enzymic hydrolysis of starch (the branch points in amylopectin) Enzymic hydrolysis of starch (amylase); germinating cereals and malt Milk (and many pharmaceutical preparations as a filler) Heated milk (small amounts), mainly synthetic Cane and beet sugar, sorghum and some fruits and vegetables Lack of lactase (alactasia) leads to lactose intolerance—diarrhea and flatulence; may be excreted in the urine in pregnancy Not hydrolyzed by intestinal enzymes, but fermented by intestinal bacteria; used as a mild osmotic laxative Rare genetic lack of sucrase leads to sucrose intolerance—diarrhea and flatulence Yeasts and fungi; the main sugar of insect hemolymph

Polysaccharides Serve Storage & Structural Functions

Starch

homopolymer, called a

glucosan

carbohydrate. constituents are or

glucan.

amylose

most important dietary source of (13 –20%), nonbranching helical structure, and

amylopectin

(80 –85%),

Glycogen

storage polysaccharide. D-glucopyranose residues (in 1 4 glucosidic linkage) with branching by means of 1 6 glucosidic bonds .

Inulin

polysaccharide of fructose ,used to determine the glomerular filtration rate,

Dextrins

are intermediates in the hydrolysis of starch.

Cellulose

insoluble -D-glucopyranose 1 4 bonds cross-linking hydrogen bonds.

Chitin

exoskeleton of crustaceans and insects.

GLYCOSAMINO GLYCANS

LARGE COMPLEX OF NEGATIVELY CHARGED HETEROPOLY SACCHARIDE CHAINS.

•ASSOCIATED WITH SMALL AMOUNT OF PROTEINS FORMING PROTEOGLYCAN •ALONG WITH COLLAGEN IT FORMS EXTRACELLULAR MATRIX

[ ACIDIC SUGAR – AMINO SUGAR] – N ACIDIC SUGAR :

•D – GLUCURONIC ACID •L – IDURONIC ACID

AMINO SUGAR:

•D – GLUCOSAMINE •D - GALACTOSAMINE

ACIDIC SUGAR:

SULPHATE & COOH – GIVE NEGATIVE GHARGE

*

KERATAN SULPHATE HAS GALACTOSE INSTEAD OF ACIDIC SUGAR

AMINO SUGAR

MAY BE SULPHATED ON C4 OR 6 ON NON ACETYLATED N

REPELLING PROPERTY OF HETEROPOLY SACCHARIDES

THE HETEROPOLYSACCHARIDES

REPEL

EACH OTHER AND REMAIN

HYDRATED

 CONTRIBUTES TO THE

RESILIENCE

OF

SYNOVIAL FLUID AND VITRIOUS HUMOR

COVALENT ASSOCIATION

IS FOUND BETWEEN GLYCANS AND PROTEINS

EXCEPTION : HYALURONIC ACID

CARTILAGE: PROTEOGLYCAN MONOMER (CONDROITIN SULPHATE) (KERATAN SULPHATE) SOME PROTEOGLYCANS SYNDECAN  VERSICAN } AGGRECAN INTEGRAL MEMBRANE EXTRACELLULAR NEUROCAN CEREBROCAN } CNS

LINKAGE

Galactose – galactose – xylose – Serine { O – GLYCOSIDIC BOND BETWEEN xylose & OH of Serine

PROTEOGLYCAN AGGREGATES

Proteoglycan monomers associated with hyaluronic acid * GAG are given as supplements in cartilage associated diseases.

Lipids

Lipids Fatty Acids

Copyright © 2005 by Pearson Education, Inc.

Publishing as Benjamin Cummings 17

Lipids

Are, • 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. 18

Types of Lipids

The types of lipids containing fatty acids are • waxes • • • fats and oils (triacylglycerols) glycerophospholipids prostaglandins The types of lipids that do not contain fatty acids are • steroids 19

Fatty Acids

Fatty acids

• acids.

are long-chain carboxylic • • • typically 12-18 carbon atoms.

insoluble in water.

saturated or unsaturated.

Olive oil contains 84% unsaturated fatty acids and 16% saturated fatty acids 21

Saturated and Unsaturated Fatty Acids

Fatty acids are •

saturated

with all single C–C bonds.

•

unsaturate d

with one or more double C=C bonds.

O C OH palmitic acid, a saturated acid O C OH palmitoleic acid, an unsaturated acid 22

Properties of Saturated Fatty Acids

Saturated fatty acids

• contain only single C–C bonds.

• are closely packed. • have strong attractions between chains.

• have high melting points.

• are solids at room temperature.

COOH COOH COOH 23

Properties of Unsaturated Fatty Acids

• • • • contain one or more cis double C=C bonds.

have “kinks” in the fatty acid chains.

H do not pack closely. have few attractions between chains.

• • have low melting points.

are liquids at room temperature.

C H C H H C C HOOC COOH “kinks” in chain 24

Melting Points of Some Fatty Acids

25

Lipids Waxes, Fats, and Oils

26

Waxes

• esters of saturated fatty acids and long chain alcohols.

• coatings that prevent loss of water by leaves of plants. 27

Fats and Oils: Triacylglycerols

• • • • also called triacylglycerols.

esters of glycerol.

produced by esterification.

fFormed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids.

28

Triacylglycerols

In a

triacylglycerol

, glycerol forms ester bonds with three fatty acids

.

29

Formation of a Triacylglycerol

glycerol + three fatty acids triacylglycerol

O CH 2 OH HO C O (CH 2 ) 14 CH 3 CH CH 2 OH OH + HO HO C O C (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 CH 2 O O C (CH 2 ) 14 CH 3 CH O O C (CH 2 ) 14 CH 3 + 3H 2 O CH 2 O O C (CH 2 ) 14 CH 3 30

Melting Points of Fats and Oils

A

fat

• is solid at room temperature.

• is prevalent in meats, whole milk, butter, and cheese.

An

oil

• • is liquid at room temperature.

is prevalent in plants such as olive and safflower.

31

Oils with Unsaturated Fatty Acids

Oils

• • • • • have more unsaturated fats.

have cis double bonds that cause “kinks” in the fatty acid chains.

with “kinks” in the chains do not allow the triacylglycerol molecules to pack closely.

have lower melting points than saturated fatty acids.

are liquids at room temperature.

32

Diagram of Triacylglycerol with Unsaturated Fatty Acids

Unsaturated fatty acid chains with kinks cannot pack closely

.

33

Percent Saturated and Unsaturated Fatty Acids In Fats and Oils

34

Lipids Chemical Properties of Triacylglycerols

35

Chemical Properties of Triacylglycerols

The chemical reactions of triacylglycerols are similar to those of alkenes and esters. • In

hydrogenation

, double bonds in unsaturated fatty acids react with H presence of a Ni or Pt catalyst.

2 in the • In hydrolysis, water in the presence of an acid, a base, or an enzyme.

ester bonds are split by 36

Hydrogenation of Oils

• • • • adds hydrogen (H double bonds.

2 ) to the carbon atoms of converts double bonds to single bonds. increases the melting point.

produces solids such as margarine and shortening. 37

Hydrogenation

O CH 2 CH O C (CH 2 ) 5 CH CH(CH 2 ) 7 CH 3 O + 3H 2 O (CH 2 ) 5 CH CH(CH 2 ) 7 CH 3 CH 2 O C CH 2 (CH 2 ) 5 CH CH(CH 2 ) 7 CH 3 CH

glyceryl tripalmitoleate (tripalmitolean )

CH 2 Ni O O O O C O C O C (CH (CH 2 2 ) ) 14 14 CH (CH 2 ) 14 CH 3 CH 3 3

glyceryl tripalmitate (tripalmitin )

38

Olestra, A Fat Substitute

Olestra

• is used in foods as an artificial fat.

• • sucrose linked by ester bonds to several long-chain fatty chains.

not broken down in the intestinal tract.

39

Cis and Trans Fatty Acids

Unsaturated fatty acids can be • cis with bulky groups on same side of C=C.

CH 3 ─ (CH 2 ) 5 (CH 2 ) 7 ─ COOH

cis

C=C H H • trans have bulky groups on opposite sides of C=C.

CH 3 ─ (CH 2 ) 5

H C=C H

(CH 2 ) 7 ─ COOH

40

Hydrogenation and Trans Fatty Acids

Most naturally occurring fatty acids have cis double bonds.

• During hydrogenation, some cis double bonds are converted to trans double bonds.

• In the body, trans fatty acids behave like saturated fatty acids. • It is estimated that 2-4% of our total Calories is in the form of trans fatty acid. • Several studies reported that trans fatty acids raise LDL-cholesterol and lower HDL cholesterol.

41

Learning Check

(1) True or (2) False A. There are more unsaturated fats in vegetable oils.

B. Vegetable oils have higher melting points than fats. C. Hydrogenation of oils converts some cis- double bonds to trans- double bonds.

D. Animal fats have more saturated fats.

42

Solution

(1) True or (2) False A.

T

There are more unsaturated fats in vegetable oils.

B.

F

Vegetable oils have higher melting points than fats. C.

T

Hydrogenation of oils converts some cis-double bonds to trans- double bonds.

D.

T

Animal fats have more saturated fats.

43

Hydrolysis

• • triacylglycerols split into glycerol and three fatty acids.

an acid or enzyme catalyst is required.

O CH 2 O C O (CH 2 ) 14 CH 3 H + CH O C O (CH 2 ) 14 CH 3 + H 2 O CH 2 O C (CH 2 ) 14 CH 3 CH 2 OH O CH OH + HO C (CH 2 ) 14 CH 3 CH 2 OH 44

Cholesterol

Cholesterol

• is the most abundant steroid in the body. • has methyl CH 3 chain, and -OH attached to the steroid nucleus.

- groups, alkyl CH 3 CH 3 CH 3 CH 3 CH 3 HO 45

Cholesterol in the Body

• is obtained from meats, milk, and eggs. • is synthesized in the liver.

• is needed for cell membranes, brain and nerve tissue, steroid hormones, and Vitamin D.

• clogs arteries when high levels form plaque.

A normal, open artery.

An artery clogged by cholesterol plaque

46

Cholesterol in Foods

• • is considered elevated if plasma cholesterol exceeds 200 mg/dL.

synthesized in the liver and obtained from foods.

Not found in Plant foods 47

Lipoproteins

• combine lipids with proteins and phospholipid s.

• soluble in water because the surface consists of polar lipids.

48

Types of Lipoproteins

• • differ in density, composition, and function.

include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs).

49