BIOMOLECULES

CARBOHYDRATES

● Polyhydroxy aldehydes or ketones or the compounds that will decompose to give

polyhydroxy aldehydes or ketones on hydrolysis.
Example : glucose, fructose, arabinose, ribose, sucrose.

CLASSIFICATION OF CARBOHYDRATES

❖ Monosaccharides: carbohydrates that cannot be hydrolysed simpler poly hydroxy

aldehydes or ketones
eg : ribose, arabinose, glucose, fructose

About 20 monosaccharides found in nature

❖ Oligosaccharides : carbohydrates that will give 2-10 monosaccharides on hydrolysis

they are again classified as,
Disaccharides- it will give monosaccharides two monosaccharides on hydrolysis
eg : sucrose, lactose
Trisaccharides-it will three monosaccharides on hydrolysis…

❖ Poly saccharides : carbohydrates that will give more than ten monosaccharides on
hydrolysis
eg : starch, glycogen

Carbohydrates are classified as reducing (eg : glucose, fructose, lactose……….) and non
reducing sugars (eg : sucrose)
● All monosaccharides are reducing sugars
● Disaccharides may be reducing (eg: lactose, maltose) and non reducing sugar (eg:
sucrose)
● Reducing sugar will reduce Tollens's reagent, Fehling solution

TYPES OF MONOSACCHRIDES

● It is of two types – Aldose and Ketose

● Aldose has aldehyde functional group and Ketose have ketonic functional group.
Glucose is an aldose and fructose is Ketose
● Based on the no. of carbon atoms it is of different types – triose (three carbon
atoms), tetrose (four carbon atoms)
● Glucose is aldohexose and fructose is ketohexose

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METHODS OF PREPARATION OF GLUCOSE

● By the hydrolysis of sucrose in acidic medium

● By the hydrolysis of starch in acidic medium

STRUCTURE OF GLUCOSE

● Based on the experimental observation given below, the following structure is

assigned for glucose
● M.F of glucose is C6H12O6
● On treatment with HI/red P, hexane is formed, which shows that all the six carbon
atom, are arranged in straight chain
● On oxidation with Br2(aq) , it gives gluconic acid which shows that glucose contains –
CHO group
● On treatment with acetic anhydride, glucose gives glucose penta acetate, which
shows that glucose contains five – OH groups.
● On treatment with conc. HNO3, glucose gives saccharic acid, which shows that, one
of the OH group in glucose is primary OH group

CYCLIC PYRANOSE STRUCTURE OF GLUCOSE

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STRUCTURE OF FRUCTOSE

DISACCHRIDES

● It is a disaccharide of α-D – glucose & β – D – fructose. Here two monosaccharides

are linked through C1 - C2 glycosidic linkage.
● On hydrolysis the dextro rotatory, sucrose gives equimolar mixture α - D – glucose &
β –D - fructose , but it is laevo rotatory.
● The mixture is called invert sugar

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MALTOSE

● It is a disaccharide of two molecules of α – D – glucose linked through C1 – C4

glycosidic linkage

LACTOSE (MILK SUGAR)

● It is a disaccharide of α – D – glucose & β – D – galactose and here glycosidic

linkage through C1– C4 carbon atom of the above two

POLYSACCHARIDES

● Starch: it is a polysaccharide of α – D – glucose and it has two components – water

soluble amylose and water insoluble amylopectin
● Cellulose: it is a polysaccharide of β – D – glucose
● Glycogen: it is also known as animal starch

IMPORTANCE OF CARBOHYDRATES

● They are storage molecules (eg: Starch, glycogen)

● Cell wall of bacteria & plants is made up of cellulose
● We build up, furniture using cellulose part of wood
● Aldo pentoses like β – D – ribose & β – D – 2 – deoxy ribose are the main
constituents of nucleic acids

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 PROTEINS
● Proteins are the polymers of α – amino acids
● It contains NH2 group (Basic) and COOH group (acidic)
● Based on the relative no. of COOH and NH groups amino acids are classified into
neutral, basic and Acidic amino acids

eg :
❖ Glycine – neutral
❖ Glutamic acid – acidic
❖ Lysine - basic

CLASSIFICATION OF AMINO ACIDS

● Essential amino acids – should be availed through diet

Eg : the valine, leucine
● Non essential amino acids – synthesised by our body
Eg: glycine, alanine
● All α – amino acids except glycine are optically active
● About 20 amino acids are found in nature

FORMATION OF ZWITTER ION

● α – amino acids can form zwitter ion (internal salt) because it contain acidic and basic
groups. Zwitter ion formation is realised through the migration of H+ from – COOH
group to – NH2 group.

● Due to zwitter ion formation, amino acids are solids with very high melting point.

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FORMATION OF PROTEINS

● Two α – amino acids, when linked through peptide linkage, a dipeptide is formed, it
becomes
tripeptide, tetrapeptide and finally polypeptide.
● Polypeptides having more than 100 amino acids and has a molecular mass 10000
amu is known as proteins. In proteins amino acids are linked through peptide linkage
(-CO-NH- )

CLASSIFICATION OF PROTEINS

● Based on the shape and their behaviour towards H2O, proteins are classified into two

1. Fibrous Protein : those are fibre like and are in soluble in H2O (Keratin,
myosin)
2. Globular protein: these are spherically shaped and are water soluble proteins
(albumin, insulin)
● Formation of proteins: it’s formation is completed at four levels

1. Primary structure: it represents sequence of amino acids in a polypeptide

2. Secondary structure: it may have α – helical or β – plated sheet structure
3. Tertiary structure: The folding of 2° structure leads to 3° structure
4. Quaternary structure:

● Denaturation of proteins: when a protein in it’s native form is subjected to heating,

change in pH it loses it’s biological activity. It is denaturation of protein
Eg : boiling of egg, curding of milk
● During denaturation, 2° and 3° structure is destroyed, but primary structure remains
intact

NUCLEIC ACIDS
● They are the polymers of nucleotides. Nucleotides are made up of a pentose sugar
(β – D – ribose/β – D – 2 –deoxy ribose) nitrogen base ( adenine, guanine,cytosine,
thymine, uracil) and phosphoric acid
● When pentose sugar is interacting with nitrogen base,through it’s first carbon, it is
nucleoside, When it is interacting with through it 5th carbon with H3PO4, it is
nucleotides are joined together through phosphodiester linkage, it is nucleic acid

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TYPES OF NUCLEIC ACIDS

● It is of two types – RNA & DNA

● RNA contains pentose sugar β – D – ribose, nitrogen bases A,G,C &U and
H3PO4
● DNA contains pentose sugar β – D – 2 – deoxy ribose, nitrogen bases
A,G,C,T and H3PO4
● In nucleic acids, the nucleotides are joined together through phosphodiester
linkage

DIFFERENCES BETWEEN DNA & RNA

RNA DNA

Single stranded Double stranded

Nitrogen bases : A, G, C, U A,G,C,T

Pentose sugar β – D –ribose Pentose sugar β – D – 2 –Deoxy

ribose

STRUCTURE OF DNA

It has double stranded structure. Here adenine of one strand linked to thymine and
another strand, where as cytosine of one strand is linked guanine of second strand
through hydrogen bonding.

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 • RNA: It is of different types – tRNA, mRNA,rRNA

DNA FINGERPRINTING

1. It is used to identify criminals

2. To identify paternity of an individual.
3. To identify dead bodies in accidents by comparing DNA’s of parents and
children.
4. To identify racial groups to rewrite biological evolution
HORMONES

● Hormones are molecules that act as intercellular messengers

● They are produced by endocrine glands into the blood stream, which transports them
to their site of action
● Some hormones are amino acid derivatives, some are polypeptides and others are
steroids.

STEROIDS AMINOACID POLYPEPTIDES

Estrogens Epinephrine Insulin

Androgens Norepinephrine Endorphins

IMPORTANCE OF HORMONES

● Insulin & Glucagon – Maintains blood glucose level.

● Thyroxine – iodinated derivative of tyrosine.(low levels of thyroxine leads to
hypothyroidism characterised by lethargyness & obesity)
● Adrenal cortex doesn’t function properly – Addison’s disease.
● Hormones secreted by gonads – development of secondary sexual characteristics
● Epinephrine & Norepinephrine – mediate responses to external stimuli.

VITAMINS

● Organic molecule that can’t be synthesised by our body and are essential for
optimum health and growth of organism
● It is of two types – water soluble and fat soluble
Eg: for water soluble vitamin – Vitamin – C&B
Eg: for fat soluble vitamin – Vitamin – A,D,E,K
● NB: water soluble vitamins cannot be stored by one body

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 Vitamins Deficiency diseases

Vitamin A Xerophthalmia, Night blindness

Vitamin B1 (Thiamine) Beri beri

Vitamin B2 (Riboflavin) Cheilosis

Vitamin B6 (Pyridoxine) Convulsions

Vitamin B12 Anaemia

Vitamin C (Ascorbic acid) Scurvy

Vitamin D Rickets

Vitamin E Muscular weakness

Vitamin K Increased blood clotting time

ENZYMES

● They are globular proteins

● They are catalysts and increase the rate of reaction by reducing the activation
energy
● They are highly specific in nature