Lipids are categorized into following 3 types:

1. Simple lipids: They are esters of fatty acids & certain alcohol. It is of 3 types:
 Neutral fats/glycerides: eg. Monoglycerides, Triglycerides, etc.
 Oils: Unsaturated fatty acids are called oils & present in plant. eg. mustard oil.
 Waxes: Saturated fatty acids of long chain are called waxes & present in animal. eg. animal fats.
Both oils & waxes are chemically inert , water insoluble & protective in function.
2. Complex lipid: They are complex due to presence of either carbohydrates or phosphates or
proteins. eg, Glycolipids , Phospholipids, Lipoprotein, etc.
3. Derived lipid: They are formed by the hydrolysis of simple & complex lipids. eg. steroids
(cholesterol).
Importance/Role of Cholesterol:
 It helps in absorption of fatty acids.
 Precursor of many sex hormones like progesterone.
Functions of Lipids/Fats:
 Lipids are rich to provide the energy fuel. It has nearly double caloric value than proteins.
 Triglycerides are the principal reserve food or main form of lipid storage in human.
 Fats deposited inner to muscles acts as insulator.
 Glycolipids are one of the components of cell membrane.
 Lipids are the solvent for fat soluble vitamins like A, D, E & K.
 Phospholipids are the constituents of membranes of various organs.
 Soap is formed from the fats by the process of saponification.
 It helps to form biological check point on endodermis (due to casparian stripes).
Nucleic Acids: They are long chain macro-molecules containing C, O, H, N & P. They are formed by
end to end polymerization of number of nucleotides. It consists of 3 components. i.e. Pentose sugar,
Nitrogenous bases & Phosphoric acid.
 Pentose sugar is of 2 types i.e. deoxyribose sugar present in DNA & ribose sugar in RNA.
 Nitrogenous bases are of 2 types i.e. purines & pyrimidines. Purine bases include Adenine (A) &
Guanine (G). They have two-ring in their structure. Pyrimidine bases include Cytosine (C),
Thymine (T), & Uracil (U). They have one-ring in their structure.
The pairing of purine bases with pyrimidine bases is known as complementary bases. It is present in
DNA. i.e.
A = T (Adenine is attached with Thymine by two- hydrogen bonds).
G ≡ C (Guanine is attached with Cytosine by three- hydrogen bonds).
 Phosphoric acid: It contains a phosphate group. It combines 2 nucleotides by a phosphodiester
bond.
So, a nucleotide is formed by the joining of one molecule of pentose sugar, one molecule of nitrogen
base & one molecule of phosphoric acid. i.e.
∴ a sugar + a base + a phosphate molecule = Nucleotide
But the combination of a sugar & a base is called nucleoside.
∴ Nucleotide = Nucleoside + a phosphate molecule
Types of Nucleic Acids: There are two types of nucleic acids i.e. DNA & RNA.
1. Deoxy-Ribonucleic Acid (DNA): It lies in the nucleus, mitochondria & plastids of all living organism
except some viruses.

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Structure of DNA: DNA is a macromolecule formed by the combination of numerous nucleotide where
a nucleotide is formed by the joining of one molecule of deoxy-ribose sugar, one molecule of nitrogen
base & one molecule of phosphoric acid. Double helical structure of DNA proposed by Watson &
Crick (in 1953) were also rewarded by the Nobel Prize.
The structure of DNA according to Watson & Crick can be summarized as follows:

1. It is double helical structure having two parallel chains of polynucleotides.

2. Both the strands are anti-parallel (i.e. one is in 5’-3’ direction & the next is in 3’-5’ direction) &
spirally coiled.
3. Sugar phosphate chain lies on the outside & nitrogen bases (purine & pyrimidine) form the core of
the helix.
4. Phosphate group in nucleotides are joined together by phosphor-diester bonds.
5. Both the strands are joined by weak hydrogen bond.
6. The distance between two strand is 20 Ao i.e. diameter of DNA.
7. There are 10 base pairs on a complete turn having 34 Ao distance. So, each base pairs are 3.4 Ao
apart each other.
8. Adenine (A) attaches to Thymine (T) by two hydrogen bond i.e. A = T & Guanine is attached with
Cytosine by three- hydrogen bonds i.e. G ≡ C.
9. The ratio of sugar & phosphate is equimolar i.e. Deoxyribose sugar/ phosphate =1.

Functions of DNA:
 It acts act as hereditary material.
 Controls all the biological activities of cells.
 Synthesizes RNA (i.e. production of RNA from DNA).
 It can replicate to form new DNA molecules (i.e. replication of DNA from DNA).
 DNA gives new combinations during meiosis by crossing over.
 It controls the growth & development of organisms.
State Chargaff’s rule.

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It is developed by Chargaff (1950) & based on structure of DNA. Some rule’s are:
 Total amount of purines is equal to the total amount of pyrimidines.
 Amount of Adenine (A) is equal to the amount of Thymine (T) & amount of Guanine (G) is equal to
the amount of Cytosine (C).
 The ratio of (A+T)/(G+C) is constant for a specie (eg. in human 1.55, etc.). The ratio is less in
primitive & more in advanced organisms. This ratio is not equal to 1.
 Sugar deoxyribose & phosphate occur in equimolar proportion.
2. Ribo- Nucleic Acid (RNA): It is a macro-molecule synthesized in
nucleus & present in nucleolus, cytoplasm, etc.
Structure of RNA:
 It is single stranded, non-helical polynucleotide chain smaller than
DNA.
 Nucleotides are arranged in linear form with 3’-5’ phosphor-diester
bonds.
 A nucleotide is formed by the joining of one molecule of ribose sugar,
one molecule of nitrogen base & one molecule of phosphoric acid.
 The nitrogen bases in RNA are Adenine, Guanine, Cytosine & Uracil.
Purines & pyrimidines are not in equal proportion.
Intramolecular pairing between the nucleotides of single strand of
RNA provides stability of RNA. Fig: Single helical structure of RNA
Function of RNA:
 Plays major role in protein synthesis.
 It acts as the hereditary material in some viruses.
Types of RNA: RNA is of three types i.e. mRNA, rRNA & tRNA.
1). Messenger RNA (mRNA): It acts as template for protein synthesis as it carries the genetic
information coded in DNA to site of protein synthesis. It is unstable.
2). Ribosomal RNA (rRNA): It is the most stable & abundant RNA. It is about 70-80 % of total
RNA. It is associated with ribosomes. It assembles the amino acids to form a protein.
3). Transfer RNA (tRNA): It works as adapter molecule to carry amino acids into the site of
protein synthesis. It is unstable & about 10-15% of total RNA.
Differentiae between DNA & RNA.
DNA RNA
DNA is double stranded. RNA is single stranded.
It contains deoxyribose pentose sugar. It contains ribose pentose sugar.
It is polymer of deoxyribose nucleotides. It is polymer of ribonucleotides.
It is hereditary material. It is not hereditary material except in some viruses.
It contains Adenine, Guanine, Thymine & Cytosine It contains Adenine, Guanine, Uracil & Cytosine
nitrogenous bases. nitrogenous bases.
The no. of purines & pyrimidines are equal. The number of purines & pyrimidines are not equal.
It is found in nucleus, mitochondria, nucleolus & It is found in nucleus & cytoplasm.
chloroplast.
DNA can form RNA. RNA can not form DNA.
It carries genetic information from parents to their It helps in protein synthesis.
offsprings.

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Enzyme: They are proteinaceous substance that increase the rate of biochemical reactions but not affect
the nature of final product. They are also called as biocatalysts or protein enzyme. They may be
chemically simple protein enzyme or complex protein enzyme. The study of composition & function of
enzyme is known as enzymology. The molecules upon which enzymes may act are called substrate.
Types: IUB (International Union of Biochemistry-1961) classified enzymes into six types i.e.
Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases & Ligases.
Characteristics/properties of enzymes:
 They are generally globular proteinaceous in structure.
 They are macromolecules.
 Most are water soluble but few are insoluble in water.
 Each enzyme has a particular PH but not variable. eg. sucrase 4.5 PH.
 All enzymes are heat sensitive i.e. between (25-35) OC.
 Specific enzyme is utilized for a particular biochemical reaction.
 All enzyme controlled reactions are reversible.
 Chemical reactions are not started by enzymes but can enhance.
Biological role (Functions) of enzymes:
 They are used in the chemical industry when extremely specific catalysts are required.
 Transcription, translation & replication are controlled by RNA polymerase, peptidyl transferase &
DNA polymerase respectively.
 Ligases catalyze to join the molecules organically. eg. synthetases combine pyruvic acid with CO2
to produce OAA (oxaloacetic acid).
 Isomerases cause rearrangement of molecular structure. eg. epimerases, aldolase, etc.
 Hydrolases catalyze the hydrolysis of ester, ether, etc. eg. amylase hydrolyze starch, etc.
 Transferases transfer a group from one molecule to another. eg. glutamate- pyruvate
transaminase, etc.
 Oxidoreductases take part in oxidation & reduction reaction. eg. nitrate reductase, etc.

Chapter 3.3 Microbial Biotechnology

It is the use of scientific and engineering principles to the processing of materials by micro-organisms to
create useful products for human society.
Following are the impacts of biotechnology in the field of microbiology:
1. In the field of Agriculture: It is used in agriculture to increase the productivity of crops by:
 Improvement of variety by hybridization and genetic engineering.
 Somatic hybridization i.e. fusion of protoplast to develop disease resistant species.
 Nitrogen fixation in non-leguminous cereals.
 Development of transgenic plants, animals, microbes, like genetically modified organisms
(GMOs).
2. In the field of Industry: It is used for the production of varieties of useful products in industries like;
 Baking industry use fermentation technology with yeast to produce bread, dosa, etc.
 Brewery industry use fermentation technology to produce alcoholic products.
 Tea and tobacco industries use different bacteria (Bacillus meatherium and Micrococcus
candisans) to purify their products.
 Dairy industry use different bacteria to produce cheese, curd, yoghurt, etc.

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3. In the field of Medicine: It is widely used in the field of medicine to control and improve the human
health by:
 Gene therapy is done to cure genetic disorder.
 Production of first-generation vaccines by using the concept of fermentation technology.
Similarly, second generation vaccines are produced by using Recombinant DNA Technology.
 Biotechnology plays an important role in the production of different pharmaceutical products like
insulin, interferon, human growth hormone, antibiotics, vitamins, monoclonal antibodies.
 Diagnosis of infectious diseases by using genetic engineering.
4. In the field of Waste Disposal Industry: The industrial microbiologist is directly involved in
developing microbial strains to detoxify wastes of industrial, agricultural or human origin.
5. In the field of Environmental Protection: Microbial biotechnology reduces the environmental
pollution by oil recovery and treatment of sewage along with waste water management.
6. In the field of Food and Beverages: Different food products like bread, dosa, butter, cheese as well as
different alcoholic beverages like wine, beer, whisky, etc are produced by the help of micro-organisms
using the concept of biotechnology i.e. fermentation technology.

Biogeochemical cycle:
The natural pathway by which a chemical elements or molecules move through both biotic & abiotic
compartments of the earth is called biogeochemical cycle. They ensure the availability & re-uses of
inorganic compound necessary for life. They are:
Carbon Cycle:
Carbon is basic constitute of all organic compound i.e. all living things are made of carbon. It is also a
part of the ocean, air & even rocks. Because the Earth is a dynamic place, carbon does not stay still.

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Green plants utilize CO2 to produce complex organic food substances like glucose, carbohydrate by the
process of photosynthesis. These substances are consumed by animals in the form of food to the
successive level of consumer. The dead body of plants and animals are decomposed by decomposers like
bacteria and fungi. Some of the carbon is return to the atmosphere in the form of CO2 during respiration
of plants, animals and micro-organisms.
Under certain condition like earthquake; large amount of organism get deposited inside the earth and
gradually transform into coal and natural gases, petroleum products under high pressure & temperature.
CO2 return to the atmosphere by the combustion process of these materials after millions of year.
Volcanic eruption may also add large amount of CO2 in the atmosphere.
The CO2 dissolve in water is transferred via aquatic organisms.

Nitrogen cycle:
It is also gaseous cycle. Nitrogen is essential elements present in all living organisms. It is used to
make amino acid, protein, enzymes, chlorophyll & nucleic acid.

Atmosphere contain large amount of nitrogen of about 78% but it can’t be directly utilized by plants &
should be converted into nitrites, nitrates or ammonia before utilization. The process of conversion of
atmospheric nitrogen into nitrates, nitrites & ammonia is called nitrogen fixation. It is carried by
following two methods:
A. Non-biological nitrogen fixation: Large amount of heat is generated during lightening so that
nitrogen get combine with oxygen to form oxides of nitrogen (NO, NO2, N2O5). They get dissolved in
rainwater where they combine with minerals to form nitrites & nitrates. Ammonia is produced in industry
by Haber’s process.

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B. Biological nitrogen fixation: It is done by some bacteria & BGA as:
i. Non-symbiotic nitrogen fixation: There are some free living bacteria like Azotobacter & Clostridium
which can fix atmospheric nitrogen.
ii. Symbiotic nitrogen fixation: Some bacteria like Rhizobium live symbiotic association with root
nodules of legume which convert atmospheric nitrogen into nitrates & provide to the plants.
Dead & decaying bodies of plants & animals along with their excreta are decomposed by bacteria & fungi
where nitrogen is return back to the atmosphere or soil by the following ways:
a. Ammonification: The dead bodies are decomposed by bacteria & fungi that change the nitrogenous
substances into ammonia. This process is called ammonification. Ammonia may be directly applied to
field as fertilizer.
b. Nitrification: The conversion process of ammonia into nitrite (by Nitrosomonas) & nitrites into
nitrates (by Nitrobacter) is called nitrification. Thus, nitrates are available in the soil which are absorbed
by the plants.
c. Denitrification: The conversion process of soil nitrates into free nitrogen by bacteria like
Pseudomonas, Bacillus denitrificans, etc is called denitrification.
Sometimes, nitrates of the soil are buried into the earth’s surface & locked up by the process of
sedimentation. These nitrates are only released when rocks are exposed by different means.

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