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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 (C3H6O3)
Tetroses (C4H8O4)
Pentoses
(C5H10O5)
Hexoses
(C6H12O6)
Heptoses
(C7H14O7)
Glycerose
(glyceraldehyde)
Erythrose
Dihydroxy
acetone
Erythrulose
Ribose
Ribulose
Glucose
Fructose
—
Sedoheptulose
GLUCOSE
Straight
chain
Haworth
projection
chair
Hemiacetal;reaction between
aldehyde and hydroxy grp.
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.

4th is Galactose , glucose , 2nd mannose.
Pentoses of Physiologic Importance.
Sugar
Source
Biochemical and Clinical
Importance
D-Ribose
Nucleic acids and
metabolic
intermediate
Structural component of nucleic
acids and coenzymes, including
ATP, NAD(P), and flavin
coenzymes
D-Ribulose
Metabolic
intermediate
Intermediate in the pentose
phosphate pathway
D-
Plant gums
Constituent of glycoproteins
D-Xylose
Plant gums,
proteoglycans,
glycosaminoglycans
Constituent of glycoproteins
L-Xylulose
Metabolic
intermediate
Excreted in the urine in essential
pentosuria
Arabinose
Hexoses of Physiologic Importance.
Sugar
Source
Biochemical Importance
Clinical Significance
D-Glucose
Fruit juices, hydrolysis
of starch, cane or beet
sugar, maltose and
lactose
The main metabolic fuel for
tissues; "blood sugar"
Excreted in the urine
(glucosuria) in poorly
controlled diabetes
mellitus as a result of
hyperglycemia
D-Fructose
Fruit juices, honey,
hydrolysis of cane or
beet sugar and inulin,
enzymic isomerization
of glucosesyrups for
food manufacture
Readily metabolized either
via glucoseor directly
Hereditary fructose
intolerance leads to
fructose accumulation
and hypoglycemia
D-
Hydrolysis of lactose
Readily metabolized
to glucose; synthesized in the
mammary gland for
synthesis of lactose in milk.
A constituent of glycolipids
and glycoproteins
Hereditary
galactosemia as a
result of failure to
metabolize galactose
leads to cataracts
Hydrolysis of plant
mannan gums
Constituent of glycoproteins
Galactose
D-
Mannose
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
DISACCHARIDES
Sugar
Source
Isomaltose
Enzymic hydrolysis of starch
(the branch points in
amylopectin)
Maltose
Enzymic hydrolysis of starch
(amylase); germinating cereals
and malt
syl-(1
l-(1
Clinical Significance
Lactose
Milk (and many pharmaceutical
preparations as a filler)
Lack of lactase (alactasia) leads to
lactose intolerance—diarrhea and
flatulence; may be excreted in the urine
in pregnancy
Lactulose
Heated milk (small amounts),
mainly synthetic
Not hydrolyzed by intestinal enzymes,
but fermented by intestinal bacteria;
used as a mildosmotic laxative
Sucrose
Cane and beet sugar, sorghum
and some fruits and vegetables
Rare genetic lack of sucrase leads to
sucrose intolerance—diarrhea and
flatulence
Trehalose
Yeasts and fungi; the main sugar
of insect hemolymph
Polysaccharides Serve Storage &
Structural Functions
Starch
homopolymer, called a glucosan or glucan. most important dietary source of
carbohydrate. constituents are amylose (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 :
AMINO SUGAR:
•D – GLUCURONIC ACID
•L – IDURONIC ACID
•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  INTEGRAL MEMBRANE
VERSICAN
EXTRACELLULAR
}
AGGRECAN
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 are
• long-chain carboxylic
acids.
• 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.
• do not pack closely.
• have few attractions
between chains.
• have low melting points.
• are liquids at room
temperature.
HOOC
H
H C
COOH
C
“kinks” in
chain
H
C
C
H
24
Melting Points of Some Fatty Acids
25
Lipids
Waxes, Fats, and Oils
26
Waxes
• esters of saturated fatty acids and longchain 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
CH2
OH
CH
OH
CH2
OH
+
HO C
O
(CH2)14CH3
HO C
O
(CH2)14CH3
HO C
(CH2)14CH3
O
CH2 O C
(CH2)14CH3
O
CH O C
(CH2)14CH3 + 3H2O
O
CH2 O C
(CH2)14CH3
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 H2 in the
presence of a Ni or Pt catalyst.
• In hydrolysis, ester bonds are split by
water in the presence of an acid, a base, or
an enzyme.
36
Hydrogenation of Oils
• adds hydrogen (H2) to
the carbon atoms of
double bonds.
• converts double bonds
to single bonds.
• increases the melting
point.
• produces solids such as
margarine and
shortening.
37
Hydrogenation
O
CH2
O
C
Ni
(CH2)5CH CH(CH2)7CH3
O
CH
+O3HC2 (CH ) CH
2 5
O
CH(CH2)7CH3
O
CH2
O
C
CH2
O
CH
(tripalmitolean)
(CH2)14CH3
O
(CH2)5CH CH(CH2)7CH3
glyceryl tripalmitoleate
C
CH2
O
O
C (CH2)14CH3
O
C
(CH2)14CH3
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.
CH3─ (CH2)5
(CH2)7─ COOH
cis
C=C
H
H
• trans have bulky groups on opposite
sides of C=C.
CH3─ (CH2)5
H
C=C
H
(CH2)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 HDLcholesterol.
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 cisdouble 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
CH2
CH
CH2
O
O
O
C
O
(CH2)14CH3
C (CH2)14CH3 + H2O
O
C
(CH2)14CH3
H+
CH2
OH
CH
OH
CH2
OH
O
+
HO C
(CH2)14CH3
44
Cholesterol
Cholesterol
• is the most abundant steroid in the
body.
• has methyl CH3- groups, alkyl
chain, and -OH attached to the
steroid nucleus. CH3
CH3
CH3
CH3
CH3
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