Biomolecules Class 11 Notes Biology Chapter 9

 Page 1


Points to Remember
Biomolecules : All the carbon compounds that we get from living tissues.
Biomicromolecules : Molecules which have molecular weights less than 
one thousand dalton. They are also known as monomers.
Biomacromolecules : Have molecular weight more than 10000 daltons 
(generally 10,000 deltons and above). They are generally polymers.
Biomacromolecules : A biomolecule a with molecular weight in the 
range of ten thousand daltons and above; found in acid insoluble fraction. e.g. 
polysaccharides, nucleic acids, proteins and lipids.
Primary and secondary metabolites :
? Primary	 metabolites	 have	 identifiable	 functions	 and	 play	 important	 roles	 in
normal physiological process eg. Amino acids, nitrogenous bases, proteins
and nucleic acid.
? Secondary metabolites are product of certain metabolic pathways from
primary metabolites, eg. carotenoids, drugs, alkaloids, essential oils, rubber,
gum, cellulose and resins etc.
 Amino acids : Organic compounds containing an amino group and one
carboxyl group (acid group) and both these groups are attached to the same
carbon atom called a carbon and so they are called  amino acids.
 e.g. (1) In Glycine R = H
 (2) In alanine R = CH
3
 (3) In serine R = CH
2
 – OH
Page 2


Points to Remember
Biomolecules : All the carbon compounds that we get from living tissues.
Biomicromolecules : Molecules which have molecular weights less than 
one thousand dalton. They are also known as monomers.
Biomacromolecules : Have molecular weight more than 10000 daltons 
(generally 10,000 deltons and above). They are generally polymers.
Biomacromolecules : A biomolecule a with molecular weight in the 
range of ten thousand daltons and above; found in acid insoluble fraction. e.g. 
polysaccharides, nucleic acids, proteins and lipids.
Primary and secondary metabolites :
? Primary	 metabolites	 have	 identifiable	 functions	 and	 play	 important	 roles	 in
normal physiological process eg. Amino acids, nitrogenous bases, proteins
and nucleic acid.
? Secondary metabolites are product of certain metabolic pathways from
primary metabolites, eg. carotenoids, drugs, alkaloids, essential oils, rubber,
gum, cellulose and resins etc.
 Amino acids : Organic compounds containing an amino group and one
carboxyl group (acid group) and both these groups are attached to the same
carbon atom called a carbon and so they are called  amino acids.
 e.g. (1) In Glycine R = H
 (2) In alanine R = CH
3
 (3) In serine R = CH
2
 – OH
92
? Twenty types of amino acids.
Amino acid exists in Zwitterionic form at different pHs.
             R R R
              | | |
     (A) (B) (C)
(Zwitterionic form)
? Based on number of amino and carboxyl groups, amino acids can be :
(i) Aromatic–Tryptophan, phenylalanine and Tyrosine are aromatic (give
smell) amino acids.
Amino Acids
 Polar
 Acidic Basic Neutral
 e.g. aspartic acid e.g., Arginine e.g. valine, Proline
 glutamic acid
 (ii) Non Polar—Glutamine, tyrosine, serine
Lipids :
Lipids are not strictly macromolecules as their molecular weight do not 
exceed 800 Da but form a part of the acid insoluble pool.
? Water insoluble, containing C, H, O.
? Fats on hydrolysis yield fatty acids.
? Fatty acid has a carboxyl group attached to an R group (contains 1 to 19
carbons).
? Fatty Acids : Saturated : With single bonds in carbon chain, e.g., Palmitic
acid, butyric acid.
 Unsaturated : With one or more double bonds, e.g., oleic acid, linoleic acid.
? Glycerol : A simple lipid, is trihydroxy propane.
? Some	lipid	have	fatty	acids	esterified 	with	glycerol.
Example of fatty acid (Palmitic acid) (CH
3
—(CH
2
)
14
—COOH)
Page 3


Points to Remember
Biomolecules : All the carbon compounds that we get from living tissues.
Biomicromolecules : Molecules which have molecular weights less than 
one thousand dalton. They are also known as monomers.
Biomacromolecules : Have molecular weight more than 10000 daltons 
(generally 10,000 deltons and above). They are generally polymers.
Biomacromolecules : A biomolecule a with molecular weight in the 
range of ten thousand daltons and above; found in acid insoluble fraction. e.g. 
polysaccharides, nucleic acids, proteins and lipids.
Primary and secondary metabolites :
? Primary	 metabolites	 have	 identifiable	 functions	 and	 play	 important	 roles	 in
normal physiological process eg. Amino acids, nitrogenous bases, proteins
and nucleic acid.
? Secondary metabolites are product of certain metabolic pathways from
primary metabolites, eg. carotenoids, drugs, alkaloids, essential oils, rubber,
gum, cellulose and resins etc.
 Amino acids : Organic compounds containing an amino group and one
carboxyl group (acid group) and both these groups are attached to the same
carbon atom called a carbon and so they are called  amino acids.
 e.g. (1) In Glycine R = H
 (2) In alanine R = CH
3
 (3) In serine R = CH
2
 – OH
92
? Twenty types of amino acids.
Amino acid exists in Zwitterionic form at different pHs.
             R R R
              | | |
     (A) (B) (C)
(Zwitterionic form)
? Based on number of amino and carboxyl groups, amino acids can be :
(i) Aromatic–Tryptophan, phenylalanine and Tyrosine are aromatic (give
smell) amino acids.
Amino Acids
 Polar
 Acidic Basic Neutral
 e.g. aspartic acid e.g., Arginine e.g. valine, Proline
 glutamic acid
 (ii) Non Polar—Glutamine, tyrosine, serine
Lipids :
Lipids are not strictly macromolecules as their molecular weight do not 
exceed 800 Da but form a part of the acid insoluble pool.
? Water insoluble, containing C, H, O.
? Fats on hydrolysis yield fatty acids.
? Fatty acid has a carboxyl group attached to an R group (contains 1 to 19
carbons).
? Fatty Acids : Saturated : With single bonds in carbon chain, e.g., Palmitic
acid, butyric acid.
 Unsaturated : With one or more double bonds, e.g., oleic acid, linoleic acid.
? Glycerol : A simple lipid, is trihydroxy propane.
? Some	lipid	have	fatty	acids	esterified 	with	glycerol.
Example of fatty acid (Palmitic acid) (CH
3
—(CH
2
)
14
—COOH)
93
? They can be monoglycerides, diglycerides and triglycerides.
1
2
3
 Triglyceride (R
1
, R
2
, R
3
 are alkyl groups in fatty acids.)
 Phospholipids (Lecithin) found in cell membrane and lipids made complex 
structure in neural tissue.
? Phospholipids are compound lipids with phosphorus and a phosphorylated
organic compound e.g., Lecithin.
Nitrogen bases
(Carbon compounds with heterocyclic rings)
 Purine : Adenine, Guanine, Pyrimidine : Cytosine, Uracil, Thymine.
Nucleoside : Nitrogenous base + Sugar e.g. Adenosine, guanosine.
Nucleotide : Nitrogenous base + Sugar + Phosphate group. e.g. Adenylic 
acid, Guanylic acid. Thymidylic acid.
Nucleic acids : Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
DNA structure (Watson and Crick Model) : DNA is a right handed, double 
helix of  two polynucleotide chains, having a major and minor groove. The two 
chains are antiparallel, and held together by hydrogen bonds (two between A 
and T and three between C and G). The backbone is formed by sugar-phosphate-
sugar chain. The nitrogen bases are projected more or less perpendicular to this, 
backbone and face inside. The pitch is 34A°. At  each step of ascent, the strand 
turns 36°. The rise per base pair is 3.4°A, so one full turn involves ten base pairs.
Protein : proteins are polypeptides.
? They are polymers of aminoacids linked by peptide bond.
? Is a heteropolymer (different monomers repeating ‘n’ number of times).
? For functions of proteins refer Table 9.5, Page no. 147 NCERT, Text Book
of Biology for Class XI.
Page 4


Points to Remember
Biomolecules : All the carbon compounds that we get from living tissues.
Biomicromolecules : Molecules which have molecular weights less than 
one thousand dalton. They are also known as monomers.
Biomacromolecules : Have molecular weight more than 10000 daltons 
(generally 10,000 deltons and above). They are generally polymers.
Biomacromolecules : A biomolecule a with molecular weight in the 
range of ten thousand daltons and above; found in acid insoluble fraction. e.g. 
polysaccharides, nucleic acids, proteins and lipids.
Primary and secondary metabolites :
? Primary	 metabolites	 have	 identifiable	 functions	 and	 play	 important	 roles	 in
normal physiological process eg. Amino acids, nitrogenous bases, proteins
and nucleic acid.
? Secondary metabolites are product of certain metabolic pathways from
primary metabolites, eg. carotenoids, drugs, alkaloids, essential oils, rubber,
gum, cellulose and resins etc.
 Amino acids : Organic compounds containing an amino group and one
carboxyl group (acid group) and both these groups are attached to the same
carbon atom called a carbon and so they are called  amino acids.
 e.g. (1) In Glycine R = H
 (2) In alanine R = CH
3
 (3) In serine R = CH
2
 – OH
92
? Twenty types of amino acids.
Amino acid exists in Zwitterionic form at different pHs.
             R R R
              | | |
     (A) (B) (C)
(Zwitterionic form)
? Based on number of amino and carboxyl groups, amino acids can be :
(i) Aromatic–Tryptophan, phenylalanine and Tyrosine are aromatic (give
smell) amino acids.
Amino Acids
 Polar
 Acidic Basic Neutral
 e.g. aspartic acid e.g., Arginine e.g. valine, Proline
 glutamic acid
 (ii) Non Polar—Glutamine, tyrosine, serine
Lipids :
Lipids are not strictly macromolecules as their molecular weight do not 
exceed 800 Da but form a part of the acid insoluble pool.
? Water insoluble, containing C, H, O.
? Fats on hydrolysis yield fatty acids.
? Fatty acid has a carboxyl group attached to an R group (contains 1 to 19
carbons).
? Fatty Acids : Saturated : With single bonds in carbon chain, e.g., Palmitic
acid, butyric acid.
 Unsaturated : With one or more double bonds, e.g., oleic acid, linoleic acid.
? Glycerol : A simple lipid, is trihydroxy propane.
? Some	lipid	have	fatty	acids	esterified 	with	glycerol.
Example of fatty acid (Palmitic acid) (CH
3
—(CH
2
)
14
—COOH)
93
? They can be monoglycerides, diglycerides and triglycerides.
1
2
3
 Triglyceride (R
1
, R
2
, R
3
 are alkyl groups in fatty acids.)
 Phospholipids (Lecithin) found in cell membrane and lipids made complex 
structure in neural tissue.
? Phospholipids are compound lipids with phosphorus and a phosphorylated
organic compound e.g., Lecithin.
Nitrogen bases
(Carbon compounds with heterocyclic rings)
 Purine : Adenine, Guanine, Pyrimidine : Cytosine, Uracil, Thymine.
Nucleoside : Nitrogenous base + Sugar e.g. Adenosine, guanosine.
Nucleotide : Nitrogenous base + Sugar + Phosphate group. e.g. Adenylic 
acid, Guanylic acid. Thymidylic acid.
Nucleic acids : Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
DNA structure (Watson and Crick Model) : DNA is a right handed, double 
helix of  two polynucleotide chains, having a major and minor groove. The two 
chains are antiparallel, and held together by hydrogen bonds (two between A 
and T and three between C and G). The backbone is formed by sugar-phosphate-
sugar chain. The nitrogen bases are projected more or less perpendicular to this, 
backbone and face inside. The pitch is 34A°. At  each step of ascent, the strand 
turns 36°. The rise per base pair is 3.4°A, so one full turn involves ten base pairs.
Protein : proteins are polypeptides.
? They are polymers of aminoacids linked by peptide bond.
? Is a heteropolymer (different monomers repeating ‘n’ number of times).
? For functions of proteins refer Table 9.5, Page no. 147 NCERT, Text Book
of Biology for Class XI.
94
Structure of Proteins
(a) Primary structure : Is found in the form of linear sequence of amino acids. 
First amino acid is called N-terminal amino acid and last amino acid is called 
C-terminal amino acid.
(b) Secondary structure : Polypeptide chain undergoes folding or coiling which 
is stabilized-by hydrogen bonding. Right handed helices are observed; e.g., 
fibrous	protein	in	hair ,	nails.
(c) Tertiary structure : Long protein chain is folded upon itself like a hollow 
woollen ball. Gives a 3-dimensional view of protein, e.g., myosin.
(d) Quaternary structure : Two or more polypeptides with their foldings and 
coilings are arranged with respect to each other, e.g., Human haemoglobin 
molecule has 4 peptide chains - 2 a and 2 ß Subunits.
 Monosaccharides are joined by glycosidic bond, right end is reducing and 
left end is non reducing
Polysaccharides : Are long chain of polymers of monosaccharides.
(a) Starch : Store house of energy in plant tissues. Forms helical secondary 
structures, made of only glucose monomers.
(b) Cellulose : Homopolymer of glucose. It does not certain complex helices. 
Cotton	fibre	is	cellulose.
(c) Glycogen : Is a branched homopolymer, found as storage polysaccharide in 
animals.
(d) Inulin : Is a polymer of fructose.
(e) Chitin : Chem icall y	 modified	 sugar	 (amino-sugars)	 N-acetyl	 galact osam ine 	
form exoskeleton of arthropods; heterpolymer.
Metabolic Pathways :
(a) Anabolic pathways : Lead to formation of more complex structure from a 
simpler structure with the consumption of energy, e.g., Protein from amino 
acids., also known as biosynthetic pathways.
(b) Catabolic pathway : Lead to formation of simpler structure from a complex 
structure, e.g., Glucose ? Lactic Acid + energy
 The most important energy currency in living systems is ATP (adenosine 
tri – phosphate).
“There is no uncatalysed metabolic conversion in living system”
The living state is a non-equilibrium steady state to be able to perform work. 
Without metabolism, there cannot be a living state.
Page 5


Points to Remember
Biomolecules : All the carbon compounds that we get from living tissues.
Biomicromolecules : Molecules which have molecular weights less than 
one thousand dalton. They are also known as monomers.
Biomacromolecules : Have molecular weight more than 10000 daltons 
(generally 10,000 deltons and above). They are generally polymers.
Biomacromolecules : A biomolecule a with molecular weight in the 
range of ten thousand daltons and above; found in acid insoluble fraction. e.g. 
polysaccharides, nucleic acids, proteins and lipids.
Primary and secondary metabolites :
? Primary	 metabolites	 have	 identifiable	 functions	 and	 play	 important	 roles	 in
normal physiological process eg. Amino acids, nitrogenous bases, proteins
and nucleic acid.
? Secondary metabolites are product of certain metabolic pathways from
primary metabolites, eg. carotenoids, drugs, alkaloids, essential oils, rubber,
gum, cellulose and resins etc.
 Amino acids : Organic compounds containing an amino group and one
carboxyl group (acid group) and both these groups are attached to the same
carbon atom called a carbon and so they are called  amino acids.
 e.g. (1) In Glycine R = H
 (2) In alanine R = CH
3
 (3) In serine R = CH
2
 – OH
92
? Twenty types of amino acids.
Amino acid exists in Zwitterionic form at different pHs.
             R R R
              | | |
     (A) (B) (C)
(Zwitterionic form)
? Based on number of amino and carboxyl groups, amino acids can be :
(i) Aromatic–Tryptophan, phenylalanine and Tyrosine are aromatic (give
smell) amino acids.
Amino Acids
 Polar
 Acidic Basic Neutral
 e.g. aspartic acid e.g., Arginine e.g. valine, Proline
 glutamic acid
 (ii) Non Polar—Glutamine, tyrosine, serine
Lipids :
Lipids are not strictly macromolecules as their molecular weight do not 
exceed 800 Da but form a part of the acid insoluble pool.
? Water insoluble, containing C, H, O.
? Fats on hydrolysis yield fatty acids.
? Fatty acid has a carboxyl group attached to an R group (contains 1 to 19
carbons).
? Fatty Acids : Saturated : With single bonds in carbon chain, e.g., Palmitic
acid, butyric acid.
 Unsaturated : With one or more double bonds, e.g., oleic acid, linoleic acid.
? Glycerol : A simple lipid, is trihydroxy propane.
? Some	lipid	have	fatty	acids	esterified 	with	glycerol.
Example of fatty acid (Palmitic acid) (CH
3
—(CH
2
)
14
—COOH)
93
? They can be monoglycerides, diglycerides and triglycerides.
1
2
3
 Triglyceride (R
1
, R
2
, R
3
 are alkyl groups in fatty acids.)
 Phospholipids (Lecithin) found in cell membrane and lipids made complex 
structure in neural tissue.
? Phospholipids are compound lipids with phosphorus and a phosphorylated
organic compound e.g., Lecithin.
Nitrogen bases
(Carbon compounds with heterocyclic rings)
 Purine : Adenine, Guanine, Pyrimidine : Cytosine, Uracil, Thymine.
Nucleoside : Nitrogenous base + Sugar e.g. Adenosine, guanosine.
Nucleotide : Nitrogenous base + Sugar + Phosphate group. e.g. Adenylic 
acid, Guanylic acid. Thymidylic acid.
Nucleic acids : Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
DNA structure (Watson and Crick Model) : DNA is a right handed, double 
helix of  two polynucleotide chains, having a major and minor groove. The two 
chains are antiparallel, and held together by hydrogen bonds (two between A 
and T and three between C and G). The backbone is formed by sugar-phosphate-
sugar chain. The nitrogen bases are projected more or less perpendicular to this, 
backbone and face inside. The pitch is 34A°. At  each step of ascent, the strand 
turns 36°. The rise per base pair is 3.4°A, so one full turn involves ten base pairs.
Protein : proteins are polypeptides.
? They are polymers of aminoacids linked by peptide bond.
? Is a heteropolymer (different monomers repeating ‘n’ number of times).
? For functions of proteins refer Table 9.5, Page no. 147 NCERT, Text Book
of Biology for Class XI.
94
Structure of Proteins
(a) Primary structure : Is found in the form of linear sequence of amino acids. 
First amino acid is called N-terminal amino acid and last amino acid is called 
C-terminal amino acid.
(b) Secondary structure : Polypeptide chain undergoes folding or coiling which 
is stabilized-by hydrogen bonding. Right handed helices are observed; e.g., 
fibrous	protein	in	hair ,	nails.
(c) Tertiary structure : Long protein chain is folded upon itself like a hollow 
woollen ball. Gives a 3-dimensional view of protein, e.g., myosin.
(d) Quaternary structure : Two or more polypeptides with their foldings and 
coilings are arranged with respect to each other, e.g., Human haemoglobin 
molecule has 4 peptide chains - 2 a and 2 ß Subunits.
 Monosaccharides are joined by glycosidic bond, right end is reducing and 
left end is non reducing
Polysaccharides : Are long chain of polymers of monosaccharides.
(a) Starch : Store house of energy in plant tissues. Forms helical secondary 
structures, made of only glucose monomers.
(b) Cellulose : Homopolymer of glucose. It does not certain complex helices. 
Cotton	fibre	is	cellulose.
(c) Glycogen : Is a branched homopolymer, found as storage polysaccharide in 
animals.
(d) Inulin : Is a polymer of fructose.
(e) Chitin : Chem icall y	 modified	 sugar	 (amino-sugars)	 N-acetyl	 galact osam ine 	
form exoskeleton of arthropods; heterpolymer.
Metabolic Pathways :
(a) Anabolic pathways : Lead to formation of more complex structure from a 
simpler structure with the consumption of energy, e.g., Protein from amino 
acids., also known as biosynthetic pathways.
(b) Catabolic pathway : Lead to formation of simpler structure from a complex 
structure, e.g., Glucose ? Lactic Acid + energy
 The most important energy currency in living systems is ATP (adenosine 
tri – phosphate).
“There is no uncatalysed metabolic conversion in living system”
The living state is a non-equilibrium steady state to be able to perform work. 
Without metabolism, there cannot be a living state.
95
Bonds linking monomers in a polymer
Peptide bond—formed between the carboxyl (–COOH) group of one amino 
acid, and the amino (– NH
2
) group of the next amino with the elimination of water 
moiety, (dehydration).
Glycosidic bond—bond formed between two carbon atoms of two adjacent 
monosaccharides., by dehydration.
Phosphodiester bond—bond formed in nucleic acids where in a phosphate 
moiety links the 3-carbon of one sugar of one nucleotide to the 5-carbon of the 
sugar of the succeeding nucleotide. (The bond between phosphate group and 
hydroxyl group of sugar)
Ezymes : Are biocatalyst.
? Almost all enzymes are proteins.
? Ribozymes–Nucleic acid that behave like enzymes.
? Has primary, secondary and tertiary structure.
? Active	site 	of	an	enzyme	is 	a	crevice	or	pocket 	into	which	substrate	fits.
? Enzymes get damaged at high temperatures.
? Enzymes isolated from thermophilic organisms (live under high temperatures)
are thermostable.
? Enzymes accelerate the reactions many folds.
? Enzymes lower the activation energy of reactions. (Fig. 9.6, Page no. 156,
NCERT Text Book of Biology for Class XI).
? E + S == ES ? EP ? E + P
where E = Ezymes, S = Substrate, P = Product
Factors affecting enzyme activity :
 (a) Temperature : Show highest activity at optimum temperature. Activity 
declines above and below the optimum value.
(b) pH : Enzymes function in a narrow range of pH. Highest activity at optimum 
pH. (Fig. 9.7, Page no. 157, NCERT, Text Book of Biology for Class XI).