Benjamin B. Jularbal, PhD.

BIOMOLECULES
• Contain only three to six different elements-
C, H, and O are always present; N, S and P
are present in some.
• Elements form a limited number of
FUNCTIONAL GROUPS.
FUNCTIONAL GROUPS
• Determines the physical properties and
chemical reactivities of the biomolecules
• Form bonds through CONDENSATION
REACTIONS.

CONDENSATION REACTIONS
• Two groups join with the release of water
• This reaction links small molecules into
macromolecules.
• Bond formation is an energy-requiring
process.
• Synthesis of macromolecules from small
molecules requires metabolic energy.
Carbohydrates
GLUCOSE

• Provides a significant portion of the

energy needed by cells in the fed
state.
• Maintained in the blood as the sole
energy source for the brain in the
nonstarving state and as an available
energy source for all other tissues.
MONOSACCHARIDES
• ALDOSES or KETOSES with the
general molecular formula (CH2O)x.
• Classified by the number of carbon
atoms and the nature of the most
oxidized group.
• Exist as OPTICAL ISOMERS, enzymes
are specific for each isomer.
• Most sugars occur as D FORMS.
• PYRANOSE SUGARS- contain a 6
membered ring.
• FURANOSE SUGARS- contain a 5
membered ring.
• REDUCING SUGARS- open-chain
forms sugars that react with reducing
agents.
MONOSACCHARIDE
DERIVATIVES
SUGAR ACIDS

• ASCORBIC ACID, is required in the

synthesis of collagen.
• GLUCURONIC ACID reacts with
bilirubin in the liver, forming
conjugated bilirubin.
• GLUCURONIC ACID is a component
of GLYCOSAMINOGLYCANS (GAGs),
which are major constituents of the
ECM.

DEOXY SUGARS

• 2-DEOXYRIBOSE is an essential
component of the
deoxyribonucleotide structure.
SUGAR ALCOHOLS
GLYCEROL
• Derived from hydrolysis of TAG
• Phosphorylated in the liver to form glycerol
phosphate, which enters the gluconeogenic
pathway.
• Liver is the only tissue with GLYCEROL KINASE
to phosphorylate glycerol.
SORBITOL
• Derived from glucose.
• Osmotically active.
• Responsible for damage to the lens (cataract
formation), Schwann cells (peripheral
neuropathy), and pericytes (retinopathy), all
associated with DM.
GALACTITOL
• derived from galactose contributes to cataract
formation in galactosemia.
AMINO SUGARS
• Replacement of the hydroxyl group with an
amino group yields GLUCOSAMINE and
GALACTOSAMINE.
• N-acetylated forms of these compounds are
present in GAGs.
SUGAR ESTERS
• Sugar forms glycosidic bonds with phosphate
or sulfate.
• PHOSPHORYLATION OF GLUCOSE after it
enters cells effectively traps it as glucose-6-
phosphate, which is further metabolized.
GLYCOSYLATION
• Refers to the reaction of sugar aldehyde with
protein amino groups to form a nonreversible
covalent bond.
• Excessive glycosylation in diabetes leads to
endothelial membrane alteration, producing
microvascular disease.
• In arterioles, glycosylation of the basement
membrane renders them permeable to protein,
producing HYALINE ARTERIOLOSCLEROSIS.
Disaccharides
COMMON DISACCHARIDES

• Disaccharides are hydrolyzed by

digestive enzymes, and the resulting
monosaccharides are absorbed into the
body.
• MALTOSE = glucose + glucose
• LACTOSE = glucose + galactose
• SUCROSE = glucose + fructose
• Sucrose, unlike glucose, fructose, and
galactose, is a NONREDUCING SUGAR.
Polysaccharide
STARCH

• Primary glucose storage form in plants.

• Has two major components, both of which can be
degraded by human enzymes
• AMYLOSE has a linear structure with a-1,4
linkages.
• AMYLOPECTIN has a branched structure with a-
1,4 and a-1,6 linkages.

GLYCOGEN

• Primary glucose storage form in animals.

• Has a-glycosidic linkages, similar to amylopectin,
but it is more highly branched.
• GLYCOGEN PHOSPHORYLASE cleaves the a-1,4
linkages in glycogen, releasing glucose units when
the blood glucose level is low.
• LIVER and MUSCLE produce glycogen from
excess glucose during the well-fed state.
CELLULOSE

• Structural polysaccharide in plants Glucose

polymer containing b-1,4 linkages
• An important component of fiber in the
diet.
• Supplies no energy because human
digestive enzymes cannot hydrolyze b-1,4
linkages.

HYALURONIC ACID

• Negatively charged polysaccharides

contain various sugar acids, amino sugars,
and their sulfated derivatives.
• These structural polysaccharides form a
major part of the extracellular matrix in
humans.
Lipids
FATTY ACIDS
• Simplest lipids.
• Composed of an unbranched hydrocarbon chain
with a terminal carboxyl group.
• In humans, fatty acids have an even number of
carbon atoms
• Oxidized to generate energy needed by cells in
the fasting state.
• Precursors in the synthesis of
TRIACYLGLYCEROL.
• LINOLEIC ACID and LINOLENIC ACID are
ESSENTIAL FA and must be supplied in the
diet.
• SHORT-CHAIN and MEDIUM-CHAIN FA occur
as metabolic intermediates.
DIETARY SHORT-CHAIN

• sources: coconut oil, palm kernel oil

• Directly absorbed in the small intestine and
transported to the liver through the portal vein.
• They also diffuse freely without carnitine
esterification into the mitochondrial matrix to be
oxidized.

LONG-CHAIN FATTY ACIDS

• Found in triacylglycerols (fat) and structural

lipids.
• Require the carnitine shuttle to move from the
cytosol into the mitochondria.
CIS-UNS. FATTY ACIDS

• Contain one or more double bonds.

• Double bonds have the cis configuration.
• Distance of the unsaturated bond from
the terminal carbon is indicated by the
nomenclature n-3 (𝜔-3) and n-6 (𝜔 -6).
• Oxidation in membrane lipids yields
products that cause membrane damage,
which can lead to hemolytic anemia (e.g.,
vitamin E deficiency).

TRANS FATTY ACIDS

• Formed in the production of margarine

and other hydrogenated vegetable oils
and are a risk factor for atherosclerosis.
Fatty Acid
Derivatives
TRIACYLGLYCEROLS

• Highly concentrated energy reserve

• Formed by esterification of fatty acids with glycerol
• Excess FA and FA synthesized from excess
carbohydrate and protein are converted to TAG and
stored in adipose cells.
PHOSPHOLIPIDS
• Derivatives of PHOSPHATIDIC ACID (diacylglycerol
with a phosphate group on the third glycerol carbon)
• Major component of cellular membranes.

PHOSPHOLIPASES
• Cleave specific bonds in phospholipids.

PHOSPHOLIPASES A1 and A2
• Remove fatty acyl groups from C1 and C2 during
remodeling and degradation of phospholipids.
• CORTICOSTEROIDS decrease phospholipase A2
activity thus decreasing the release of arachidonic
acid.

PHOSPHOLIPASE C
• Liberates DAG and INOSITOL TRIPHOSPHATE, two
potent intracellular signals.

PHOSPHOLIPASE D
• Generates phosphatidic acid from phospholipids.
LUNG SURFACTANT

• Decreases surface tension in the alveoli;

prevents small airways from collapsing
• Contains phospholipids-
PHOSPHATIDYLCHOLINE

RESPIRATORY DISTRESS
SYNDROME

• Hyaline membrane disease associated

with insufficient lung surfactant
• Leads to partial lung collapse and impaired
gas exchange
• Most frequent in premature infants and in
infants of diabetic mothers
SPHINGOLIPIDS

• Derivatives of ceramide, which

is formed by esterification of a
fatty acid with the amino group
of SPHINGOSINE.
• Localized mainly in the white
matter of the CNS.
• Hereditary defects in the
lysosomal enzymes that
degrade sphingolipids cause
SPHINGOLIPIDOSES.
SPHINGOMYELINS
• Phosphorylcholine attached to
ceramide
• Found in cell membranes
• Essential for Signal transduction

CEREBROSIDES
• One galactose or glucose unit joined in
b-glycosidic linkage to ceramide
• Found largely in myelin sheath

GANGLIOSIDES
• Oligosaccharide containing at least
one sialic acid residue linked to
ceramide
• Found in myelin sheath
STEROIDS

• Steroids are lipids containing a characteristic

fused ring system with a hydroxyl or keto group
on carbon 3.

CHOLESTEROL

• Most abundant steroid in mammalian tissue.

• Modulates membrane fluidity
• Precursor for synthesis of steroid hormones,
skin-derived vitamin D, and bile acids
• CHOLESTEROL: 27 carbons
• BILE ACIDS: 24 carbons (derived from
cholesterol)
• PROGESTERONE and ADRENOCORTICAL
STEROIDS: 21 carbons
• ANDROGENS: 19 carbons
• ESTROGENS: 18 carbons
EICOSANOIDS

• Eicosanoids function as short-range, short-

term signaling molecules.
• Two pathways generate three groups of
eicosanoids from ARACHIDONIC ACID.
• ARACHIDONIC ACID is released from
membrane phospholipids by phospholipase
A2
PROSTAGLANDINS

• Formed by the action of cyclooxygenase on

arachidonic acid
• PROSTAGLANDIN H, the first stable
prostaglandin which is the precursor for other
prostaglandins and THROMBOXANES.
• Biologic effects of prostaglandins are:
§ Promote acute inflammation
§ Stimulate or inhibit smooth muscle
contraction.
§ Promote vasodilation- afferent arterioles
§ Promote vasoconstriction- cerebral vessels.
§ Promote Pain in acute inflammation
§ Production of fever
THROMBOXANE A2

• Produced in platelets by the action of

thromboxane synthase on PGH2
• TXA2 strongly promotes arteriole
contraction and platelet aggregation.

ASPIRIN and NSAIDs

• Acetylate and inhibit cyclooxygenase

• Reduces synthesis of prostaglandins
(anti-inflammatory effect) and of
TXA2 (antithrombotic effect due to
reduced platelet aggregation.
LEUKOTRIENES (LT)
• Noncyclic compounds whose synthesis begins with
the hydroxylation of arachidonic acid by
LIPOXYGENASE

LEUKOTRIENE B4 (LTB4)
• Strong chemotactic agent for neutrophils and activates
neutrophil adhesion molecules for adhesion to
endothelial cells.
SLOW-REACTING SUBSTANCE OF
ANAPHYLAXIS
• Which contains LTC4, LTD4, and LTE4, is involved in
allergic reactions.

ANTILEUKOTRIENE DRUGS
• ZILEUTON, which inhibits lipoxygenase.
• ZAFIRLUKAST and MONTELUKAST, which
block leukotriene receptors on target cells.
• These drugs are used in the treatment of asthma,
because LTC4, LTD4, and LTE4 are potent
bronchoconstrictors.