properties, classification and nature of carbohydrates, lipids, nucleic acid

1. BIOMOLECULES
DEVIPRIYA P V
M PHARM
CARBOHYDRATES LIPIDS NUCLEIC ACID

2. BIOMOLECULES
 Biomolecules can be defined as the molecules that are
produced by living organisms and form the structural
basis of all living organism.
 Also called Biogenic molecules.
 Consists manly of carbon and hydrogen with nitrogen,
oxygen, sulphur and phosphorous
 They include macromolecules like carbohydrates,
proteins, lipids and nucleic acids
 It also includes small molecules like primary and
secondary metabolites and natural products.

3.  The most common biomolecules are carbohydrates, proteins,
lipids, nucleic acids and vitamins.
 Biomolecules are large molecules of many atoms that are
covalently bound together.

5. THE MAJOR COMPLEX BIOMOLECULES OF CELLS
Biomolecule Building block Major functions
Protein Amino acids Fundamental basis of
structure and function
of cell
Deoxyribonucleic acid
(DNA)
Deoxyribonucleotides Hereditary information
Ribonucleic acid (RNA) Ribonucleotides Protein synthesis
Polysaccharide
(glycogen)
Monosaccharide
(glucose)
Storage form of energy to
meet short term demands
Lipids Fatty acids & glycerol Storage form of energy to
meet long term demands

6. CARBOHYDRATES
 Carbohydrates are the most abundant organic molecules
in nature.
 Primarily composed of carbon , hydrogen & oxygen.
 The term carbohydrate means hydrates of carbon
 Carbohydrates may be defined as polyhydroxy aldehydes
or ketones or compounds which produce them on
hydrolysis.
 Carbohydrates are often referred as saccharides (sugar)

7. FUNCTIONS OF CARBOHYDRATES
1. Most abundant dietary source of energy (4 cal/g)
2. Precursors for many organic compounds (fats, amino
acids)
3. Present (as glycoproteins and glycolipids) participate in
the structure of cell membrane and cellular functions such
as cell growth, adhesion and fertilization
4. They are structural components of many organisms.
These include the cellulose in plants, exoskeleton of
some insects, cell wall of microorganisms
5. Serve as the storage form of energy (glycogen) to meet
the energy demands of the body.

8. CHEMICAL NATURE AND CLASSIFICATION OF
CARBOHYDRATES
 Based on number of sugar units:
1. Monosaccharides
: aldoses
: ketoses
2. Oligosaccharides
: disaccharides
: trisaccharides etc
3. Polysaccharides
: homopolysaccharies
: heteropolysaacharides

10. Monosaccharides:
 Simplest sugars and cannot be further hydrolysed.
 sweet to taste, crystalline in character and soluble in water
 General formula Cn(H2O)n.
 Further classified based on functional group and number of
carbon atoms
classification based on functional group :
1. Aldoses:
 Functional group is aldehyde.
Eg: glyceraldehyde, glucose
2. Ketoses:
 Functional group is keto group.
Eg: dihydroxyacetone , fructose.
Classification based on no: of c-atoms:
:Trioses(3 C), Tetroses (4C), Pentoses(5C) etc

11. .
Oligosaccharides:
 Consists of 2-10 monosaccharide units.
 Subdivided based on no: of monosaccharide units.
Disaccharides :
 Consists of 2 monosaccharide units (similar or dissimilar)
held together by glycosidic bond.
 They are crystalline, water soluble and sweet to taste
 It can be reducing or non- reducing
 Reducing: contain free aldehyde / keto group.
-Eg: maltose, lactose
 Non-reducing: contain no free aldehyde / keto group
-Eg:sucrose, trehalose.

12. Polysaccharides (glycans)
 Polymers of monosaccharide units with high molecular
weight
 Liberates 10 or more monosaccharide units on hydrolysis.
 Usually tasteless and form colloids with water.
 The polysaccharides are of two types:
Homopolysaccharies:
 Hydrolysis yield only single type of monosaccharide
 Eg: starch, glycogen, inulin, chitin, cellulose
Heteropolysaacharides:
 Hydrolysis yield a mixture of a few monosaccharide or
their derivatives.
 Eg:proteoglycans, glucosaminoglycans

15. Monosaccharide Biochemical importance
Glyceraldehyde Glyceraldehyde 3-phosphate is an intermediate in glycolysis
Dihydroxyacetone Its 1-phosphate is an intermediate in glycolysis
D-Erythrose Its 4-phosphate is an intermediate in carbohydrate metabolism
D-Ribose For the structure of RNA and nucleotide coenzymes(ATP, NAD+
, NADP+)
D-Deoxyribose For the structure of DNA
D-Ribulose It is an important metabolite in hexose monophosphate shunt
D-Xylose Involved in the function of glycoproteins
L-Xylulose Excreted in urine in essential pentosuria
D-Lyxose As a constituent of lyxoflavin of heart muscle
D-Glucose The sugar fuel of life ; excreted in urine in diabetes ; structural
unit of cellulose in plants
D-Galactose Converted to glucose, failure leads to galactosemia
D-Mannose For the structure of polysaccharides
D-Fructose Its phosphates are intermediates of glycolysis
D-Sedoheptulose Its 7-phosphate is an intermediate in HMP shunt, and in
photosynthesis

16. Disaccharides Biochemical importance
Sucrose Most commonly used table sugar supplying calories
Lactose Exclusive carbohydrate source to breast fed infants.
Lactose deficiency (lactose intolerance) leads to diarrhea and
flatulence
Maltose An important intermediate in the digestion of starch

17. LIPIDS
 Lipids may be regarded as organic substances
relatively insoluble in water, soluble in organic
solvents (alcohol, ether etc.), actually or potentially
related to fatty acids and utilized by living cells.
 Lipids are heterogeneous group of compounds

18. FUNCTIONS OF LIPIDS
1. They are the concentrated fuel reserve of the body
(triacylglycerols).
2. Lipids are the constituents of membrane structure and
regulate the membrane permeability (phospholipids
and cholesterol).
3. They serve as a source of fat soluble vitamins(A, D, E
& K).
4. Lipids are important cellular metabolic regulators
(steroid hormones and prostaglandins).
5. Lipids protect the internal organs, serve as insulating
materials and give shape and smooth appearance of
the body

19. CLASSIFICATION AND CHEMICAL NATURE OF
LIPIDS
CLASSIFICATION OF LIPIDS

20.  Classified into
1. Simple lipids
2. Complex lipids
3. Derived lipids
4. Miscellaneous lipids
Simple lipids:
 Esters of fatty acids with alcohol.
 Fatty acids(carboxylic acid with hydrocarbon side
chain) are the simplest form of lipids.
 Both saturated (do not contain double bonds) and
unsaturated fatty acids (contain one or more double
bonds) almost equally occur in the natural lipids.
 The fatty acids that cannot be synthesized by the body
and hence supplied through diet are essential fatty
acids (EFA) eg: arachidonic acid.

21.  EFA are required for the membrane structure and
function, transport of cholesterol, formation of
lipoproteins, synthesis of eicosanoids, prevention of fatty
liver etc
 Simple lipids are of two types:
(a)Fats and oils (triacylglycerols):
 These are esters of fatty acids with glycerol.
 Triacylglycerols (triglycerides) are the most abundant
group of lipids that primarily function as fuel reserves of
animals
 Triacylglycerols undergo properties like Hdrolysis,
Saponification, Rancidity and In-vivo lipid peroxidation
 The difference between oil and fat is only physical (oil is
a liquid and fat is solid at room temperature)
 Insoluble in water and non-polar in character

22. (b)Waxes:
 Esters of fatty acids(usually long chain) with
alcohol (aliphatic or alicyclic) other than glycerol.
 Cetyl alcohol is most commonly found in waxes

23. Complex(compound lipids):
 These are esters of fatty acids with alcohols containing
additional groups such as phosphate, nitrogenous base,
carbohydrate, protein etc.
 They are further divided as follows:
(a)Phospholipids:
 In addition to alcohol and fatty acids, they contain
phosphoric acid and frequently a nitrogenous base.
 Glycerophospholipids(major lipids that occur in the
biological membrane) contain glycerol as alcohol
 Eg: lecithin.
 Spingophospholipids contain sphingosine as alcohol
 Eg: sphingomyelin
(b)Lipoproteins
 Macromolecular complexes of lipids with proteins
 They are transport vehicles for lipids in the circulation.

24.  Lipoproteins are of 5 types, namely chylomicrons, very
low density lipoproteins (VLDL), low density lipoproteins
(LDL), high density lipoproteins (HDL) and free fatty
acid- albumin complexes.
(c)Glycolipids:
 These lipids contain a fatty acid, carbohydrate and
nitrogenous base.
 The alcohol is sphingosine, hence they are also called
as glycosphingolipids.
 Glycerol and phosphate are absent
 Eg: cerebrosides, gangliosides
(d)Other complex lipids:
 sulpholipids , aminolipids and lipopolysaccharides are
among the other complex lipids

25. Derived lipids:
 These are the derivatives obtained on the hydrolysis of simple
and complex lipids which posses the characteristics of lipids .
 These include glycerol and other alcohols, fatty acids, mono and
diglycerols, fat soluble vitamins, steroid (cholesterol, bile acids,
vitamin D, sex hormones, adrenocortical hormones),
hydrocarbons and ketone bodies.
Miscellaneous lipids:
 These include a large number of compounds posessing the
characteristics of lipids.
 Eg: carotenoids, squalene, hydrocarbons such as
pentacasone(in bees wax), terpenes etc.
NEUTRAL LIPIDS:
 The lipids which are uncharged
 These are mono, di and triacylglycerols, cholesterol and
cholesteryl esters

26. NUCLEIC ACID
 There are two types of nucleic acids, namely
Deoxyribonucleic acid (DNA) and
Ribonucleic acid (RNA).
 Nucleic acid serve as repositories and transmitters
of genetic material

27. FUNCTIONS OF NUCLEIC ACIDS
 DNA is the chemical basis of heredity and regarded as the
reserve bank of genetic information
 DNA is exclusively responsible for maintaining the identity
of different species of organisms.
 Every aspects of cellular information is under the control of
DNA.
 The DNA is organized into genes, the fundamental units of
genetic information.
 The genes control the protein synthesis through the
mediation of RNA.
DNA RNA Proteins
 The interrelationship of these three classes of biomolecules
(DNA, RNA and proteins) constitute the central dogma of
molecular biology or central dogma of life

28. Components of Nucleic acids:
 Nucleic acids are the polymers of Nucleotides
(polynucleotides) held by 3´ and 5´ phosphate bridges
 ie, nucleic acids are build up of monomeric units-
nucleotides (building blocks of nucleic acids)
 Nucleotides are composed of a nitrogenous base, a
pentose sugar and a phosphate.
 The term nucleoside refers to base+ sugar
 Thus Nucleotide is nucleoside + phosphate

29.  The nitrogenous bases found in nucleotides are of two
types – purines and pyrimidines (these are aromatic
heterocyclic compounds)


30. DNA and RNA contain the same purines namely adenine(A) and
Guanine(G). Further the pyrimidine Cytosine(C) is also present in both DNA
nad RNA. They differ in the second pyrimidine base. DNA contain
Thymine(T) whereas RNA contains Uracil(U)

31. Sugars of Nucleic acid:
 The five carbon monosaccharides (pentoses) are
found in the nucleic acid structure.
 RNA contains D-ribose while DNA contains D-
deoxyribose
 Ribose and deoxyribose differ in structure at carbon-2.
 Deoxyribose has one oxygen less at C2 compared to
ribose

32.  The pentoses are bound to nitrogenous bases by β-N-
glycosidic bonds
 Nucleoside monophosphates possess only one
phosphate moiety(AMP, TMP etc)
 The addition of second or third phosphates to the
nucleoside results in nucleoside diphosphates (eg:
ADP) or triphosphates (eg: ATP) respectively

33. DNA:
 Polymer of deoxyribonucleotides.
 The monomeric deoxynucleotides in DNA are held
together by 3´,5´-phosphodiester bridges.
 The salient features of Double helical structure of DNA
proposed by Watson and Crick are follows:
(1)The DNA is a right handed double helix consists of gtwo
polydeoxyribonucleotide cahins twisted around each other
on a common axis.
(2)The 2 strands are antiparallel( one strand runs in 5´ to 3´
direction while the other in 3´ to 5´ direction)
(3)The diameter of a double helix is 20 Å(2nm)
(4)Each turn of helix is 34 Å with 10 pairs of nucleotides,
each pair placed at a distance of 3.4 Å

34. (5)Each strand of DNA has 3´,5´-
phosphodiester bonds (hydrophilic) on
the periphery and the hydrophobic
bases are stacked inside
(6)The two polynucleotide chains are
complementary to each other due to
base pairing.
(7)The 2 strands are held by hydrogen
bonds formed by the complementary
base pairs.
(8)The H-bonds are formed between a
purine and pyrimidine only
(9)The content of adenine equals to
thymine (A=T) and guanine equals to
that of cytosine(G=C)
(10)The genetic information resides on
one of the two strands known as
template strand or sense strand. The
opposite strand is antisense strand

35. RNA
 RNA is a polymer of ribonucleotides held together by
3´,5´-phosphodiester bridges.
 The 3 major types of RNA are :
1. Messenger RNA(mRNA)
2. Transfer RNA(tRNA)
3. Ribosomal RNA(rRNA)