Biomolecules are the basic building blocks and molecules of life. They include both organic compounds like carbohydrates, proteins, lipids, and nucleic acids as well as inorganic compounds like water and minerals. Carbohydrates include monosaccharides, oligosaccharides, and polysaccharides and serve many functions in the body including energy storage. Proteins are made of amino acids and are essential for growth, tissue repair, enzyme production, and other functions. Lipids include fats, oils, waxes, and other compounds and store energy and insulate the body. Nucleic acids like DNA and RNA contain the genetic code and DNA has a double helix structure.

1. Biomolecules PHSS BIOLOGY CLASS NOTES
The basic and essential molecules of life are biomolecules.they are also called life components. They
form the building block and molecular basis of life. They are very simple to complex in nature.
 Simple molecule: Carbondioxide, Water
 Complex molecule: Protein, DNA, RNA
These life components are of two kinds:
 Organic Compounds: Carbohydrates, Protein, Fats and Nucleic acids
 Inorganic Compounds: Water, Minerals and Salts
Carbohydrates
Carbohydrates are the compounds of Carbon hydrogen and oxygen where hydrogen and oxygen are
present in the ratio of 2:1 as in water. The general formula is CnH2nOn. They are also known as
saccharides. Carbohydrate divides in 3 types.
i) Monosaccharides: these are the simplest form of the carbohydrate containing carbon
number 3-7. These carbohydrates can’t be hydrolysed into simpler form.
They are
3 Carbon=Trioses, 4 Carbon = Tetrose, 5 Carbon= Pentose, 6Carbon= Hexose, 7 Carbon= Heptose
For e.g. glucose, fructose etc. they are soluble in water and usually sweet in taste.
ii) Oligosaccharides:The oligosaccharides contain 2-10 monosaccharides (monomers) joined
together by glycosidic bond. These are
a. Disaccharides: Disaccharides are formed by two molecules of the monosaccharides.
Glucose + Glucose= Maltose
Glucose+ Galactose= Lactose
Glucose+ Fructose= Sucrose
b. Trisaccharides: These are made up of 3 monosaccharides molecules. Eg Raffinose is composed
of glucose, fructose and galactose.
iii) Polysaccharides
Polysaccharides are formed by the large number of monosaccharides and having several million
molecular weights. They are insoluble in water and not sweet in taste. Most important Polysaccharides
 Starch: - - - + glucose+glucose+glucose+glucose + - - -
 Cellulose:- - - + glucose+glucose+glucose+glucose + - - - -
 Other examples are glycogen, pectin etc.
Function of carbohydrate

2. • Provides energy (energy value ~ 4 kcal/g)
• Excess carbohydrate changes into fat and protein
• Essential for utilization/oxidation of fat
• Carbohydrates like cellulose, chitin are used for formation of cell wall in plant
cells and fungi
• Cellulose provide fecal bulk which facilitates the elimination
• Lactose encourages the growth of favorable intestinal bacteria. It has laxative
properties and enhance the absorption of the calcium
• Heparin (polysaccharide) is a anticoagulant found in blood prevents blood from
clotting.
• Some carbohydrates are hormone
• It gives flavor and sweetness to food
B. Amino acids: Amino acids are building blocks of proteins. They are micromolecule having carbon,
hydrogen and oxygen group. Each amino acid is a nitrogenous compound having an acidic carboxyl (-
COOH) and a basic amino (-NH2) group. About 20 amino acids are occurring naturally. According to
the body which synthesis amino acid it can be divided into two types, i.e. essential and non-essential.
Essential protein Non-essential protein
1. These amino acids cannot besynthesized by our body.
2. These amino acids must be supply through diet.
3. These include Isoleucine, leucine, lysine, threonine,
valine.
1. These amino acids can be synthesized by our body.
2. These amino acid are abundant in our body.
3. These include glutamic acid, aspartic acids, glycine,
tyrosine, arginine, ornithine, taurine, histidine, serine,
proline, asparagine, alanine
C. Proteins
Proteins are the macromolecules of amino acids. They are formed of C, H, O, N, S, P. The amino acids
are the building blocks of protein. Several amino acids join together by the peptide bond to form
proteins. Protein is found in every part of the body . Proteins can be classified into three types. They are
i) Simple protein: Proteins formed by amino acids only, e.g. albumin, globulin
ii) Conjugate protein: Protein which contain amino group as well as some non protein structure
examples

3. Glycoprotein: glucose + protein e.g saliva
Phosphoprotein: amino acid + phosphate e.g casein of milk
Lipoprotein: amino acid + lipid e.g protein of brain
iii) Derived proteins: Those proteins which are formed by the partial hydrolysis of simple and
conjugated protein. E.g. proteoses
Function of proteins
• Proteins are essential for all life forms. In human body they have the following functions:
• Body building, growth and renewal of tissue
• Synthesis of enzyme, DNA, RNA , blood proteins and hormones of protein nature
• Provides energy (energy value =4 kcal/gm)
• Defense mechanism (as antibodies)
• Metabolic regulation by enzymes (because enzymes are also protein)
• Contractile Proteins are involved in muscle contraction and movement.
• Structural Proteins are fibrous and stringy and provide support to hair.
• Transport Proteins are carrier proteins which move molecules from one place to another around
the body. Examples include hemoglobin.
• Protein helps keep skin, hair, and nails healthy.
D. Lipids or Fats
Fats are the complex molecules that constitute a mixture of fatty acid and glycerol. Like carbohydrate it
contains Carbon, Hydrogen and Oxygen but oxygen is less in compared to carbohydrates. Fatty acid is
the simplest unit of fat. These are oily and greasy organic substance, relatively insoluble in water and
soluble in organic solvents like ether, chloroform and benzene. Thus, they are hydrophobic in nature.
Classification of fatty acid
On the basis of type of bond between the carbon atoms, fatty acids are classified as
 Unsaturated fatty acid
 Saturated fatty acid
Unsaturated fatty acid Saturated fatty acid
1. Have one or more double bond between the
carbon atoms
1. Have no double bond between the carbon
atoms
2. Melt at lower temperature 2. Melt at higher temperature
Example:
Oleic acid-one double bond
Linoleic acid-two double bond
Example:
Palmitic acid
Stearic acid
Classification of fats
Fats can be grouped into three main groups
1. Simple lipids: These are ester of fatty acid and alcohol. Simple fat is categorized into following
type.
a) Neutral fat: these are the esters of fatty acid and glycerol. Hence also called as glycerides.
b) Oils: these are the fats which is liquid at room temperature. It is rich in unsaturated fatty acid
c) Waxes: these are the esters of fatty acid and long chain alcohol. It is chemically inert.

4. 2. Compound lipids: These are ester of fatty acids with alcohol and possess additional groups also. i.e.
a) Glycolipids: carbohydrate and lipid
b) Phospholipid: phosphoric acid and lipid
c) Lipoprotein: lipid and protein
3. Derived lipids: these are the substance derived from simple and compound lipids by hydrolysis.
These includes fatty acids, alcohols, mono and di-saccharide etc. e.g. Cholesterol.
Importance: It is a precursor molecule of many sex hormones like testosterone, progesterone etc. It is not
bad but not useful as well.
Function of fats
 Concentrated source of energy (energy value of 1 gram of fat ~ 9.4 kcal)
 It is the structural component of the cell membrane
 Supplies fat soluble vitamins (Vitamin A, D, E and K)
 It is the structural component of the cell membrane
 It is the raw material of all steroid hormone e.g Sex hormone
 It is required for formation of bile
 Fat acts as an insulation and helps on retain the body heat
 Fat provides a protective padding to vital organs from mechanical shock and keeps them in
place. Under skin layer they act as insulator
 Proper function of nervous system
 Normal development and function of retina
 Regular heart beat
E. Nucleic acid
Nucleic acid are the complex, long chain compound that contains C, O, H, N, P. they are the basis of
genetic materials of all organisms. The simplest unit of nucleic acid is nucleotids. Nucleotide is
composed of three component
i) Pentose sugar: Sugar having 5 carbon atoms. Ribose Sugar and Deoxy-ribose sugar
ii) Phosphate: the phosphate in the DNA is present as phosphoric acid (H3PO4).
iii. Nitrogenous Bases: the nitrogenous bases are of two types- Purine and pyrimidine. Purine bases
comprise mainly adenine (A) and guanine (G) while pyrimidine bases comprise cytosine (C) , thymine
(T) and Uracil(U).
Nucleoside: nitrogenous base + sugar
Nucleotide: nucleoside + phosphate
Types of Nucleic acids
a. Deoxyribonucleic acid (DNA)
b. Ribonucleic acid (RNA)
Watson and crick’s model of DNA

5. J.D. Watson and F. crick (1953) purposed a double helix model for DNA molecule. This model is
widely accepted. According to this model the characteristics of DNA are as follows.
a. DNA molecule consists of two strands, which are connected together by hydrogen bonds and helically
twisted.
b. the two strands are antiparallel (if one is in 3’-5’ direction, the other is in 5’-3’ direction)
c. the outer side is composed of pentose sugar and phosphoric acid while the central position is occupied
by nitrogen bases.
d. the width between two strand is 20A0 and each strand takes a complete turn after 34A0.
e. two nitrogen base are at a distance of 3.4A0 so there are 10 nitrogen bases at one turn (34A0)
f. the nitrogen bases attached to the strand are always specific i.e if one strand have purine then
pyrimidine in next. Therefore, the two strands are complementary to each other.
g. Bases of two nucleotide form hydrogen bond i.e. A combines with T by two H-bond (A=T) and G
combines with C by three hydrogen bond.
Structure of RNA
The RNA is usually single stranded polynucleotide chain. The single strand of the RNA is folded either
at certain regions or entirely to form hairpin shaped structure. The RNA dose not possess equal purine-
pyrimidine ratio, as is found in the DNA. It contains nitrogen bases Adenine (A), Guanine (G), Cytosine
(C) and Uracil (U). Thyamine is not found in RNA.

6. RNA is of three types:
1. m-RNA(messenger RNA): it constitutes about 5% - 10% of the total RNA present in the cell, m-
RNA carries the genetic information from DNA for Protein synthesis.
2. r- RNA(Ribosomal RNA): It makes about 80% of the total RNA in the cell. It is the major component
of ribosomal.
3. t RNA (Transfer RNA): it is also known as soluble RNA. It forms about 10% - 15% of the total RNA.
It used to transfer amino acid molecule to the site of protein synthesis.
F. Minerals
Minerals are the inorganic substances that are essential for the growth and development of the living
organism. Those minerals which are essential for the growth and survival of organism are called
essential elements. Some minerals are required in high amount for the growth and are called
macronutrient. The macronutrients are calcium, nitrogen, phosphorus, sodium, chlorine, magnesium and
sulphur. Some minerals are required in small amount and they are called as micronutrient. The
micronutrients are iron, copper, cobalt, zinc, manganese, molybdenum, fluorine, iodine and selenium.
G. Water (H2O):
Water is the mother liquor of all forms of life. It is very much essential for every form of life. In human
adult total body water accounts for about 70% of the lean body mass. In plant it makes about 70%-90%
of the living matter of active cells.
Function of water
i) Water is a universal solvent.

7. ii) It is used as a raw material in photosynthesis.
iii) It also helps in transpiration due to turgor pressure.
iv) It also maintains the turgidity of cells and their organelles.
v) it is used to transfer food materials with blood.
vi) it maintains human body temperature at normal (370C)