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BIO MOLECULES
Proteins are the most abundant bio molecules of the living system
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All proteins are polymers of α- amino acids
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Depending upon the relative position of amino group with respect to
carboxyl group, the amino acids can be classified as α, β, γ, and so on
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α- amino acids have trivial names, example- glycine is so named since it has
sweet taste , tyrosine was first obtained from cheese
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Of amino and carboxyl groups in their molecule
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Of
amino and carboxyl groups make it neutral, more no
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Of carboxyl groups as compared to amino
groups make it acidic
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Eg- alanine, asparagines,
aspartate etc
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Eg- valine, leucine, histidine etc
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And behave like salts rather than simple amines or carboxylic
acids, due to the presence of both acidic and basic group in the same
molecule
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This is neutral but contains positive

and negative charges
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α- amino acids are optically active (except- glycine)
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Most naturally occurring amino acids have L- configuration
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Peptide linkage is an amide formed between –COOH and –NH2
group
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This result in the elimination of a water
molecule and formation of a peptide bond –CO-NH-
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Tripeptide- if a third amino acid combines to a dipeptide, the product is
called a tripeptide
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Polypeptides- when the number of amino acids is more than 10 and they
linked together then the products are called polypeptides
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Protein classified into two types on the basis of their
molecular shape----------Fibrous proteins- when the polypeptide chains run parallel and are held
together by hydrogen and disulphide bonds, then fibre like structure is formed

such proteins are called fibrous proteins
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Egkeratin ( present in hair, wool, silk)

Globular proteins- in this type of proteins the chains of polypeptide coil
around to give a spherical shape
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Eg- insulin,
albumins, etc
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Primary structure- each polypeptide in a protein has amino acids linked
with each other in a specific sequence and this sequence of amino acids said to
be the primary structure of that protein
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2ndry structure- The secondary structure of protein refers to the shape in
which a long polypeptide chain can exist
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β structure- All peptides chains are stretched out to nearly maximum
extension and then laid side by side which are held together by intermolecular
hydrogen bonds
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Due to this
folding, globular and fibrous two major molecular shapes formed
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Denaturation of proteins- The secondary or tertiary structure of proteins
get disturbed on change of PH or temperature and they are not able to

perform their functions
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eg- coagulation
of egg white on boiling , curdling of milk etc
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They are very specific and selective in their action and
chemically all enzymes are proteins ( globular proteins )
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Vitamins- vitamins are the accessory food factors required in the diet
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Excess of vitamins is also
harmful
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They are stored in liver and adipose (
fat storing ) tissues
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Water soluble vitamin must be
supplied regularly in diet because they are readily excreted in urine and cannot
be stored
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Carbohydrates/ saccharides- It is defined as optically active polyhydroxy
aldehydes or ketones or the compounds which produce such units on
hydrolysis
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Lactose- sugar present in milk is known as lactose, also known as milk sugar
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Classification based on their behaviour on hydrolysis
1
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Eg- glucose, fructose,
ribose etc
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Oligo saccharides- Carbohydrates that yield two to ten mono saccharides
units on hydrolysis are called oligosaccharides
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Of mono
saccharides
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Poly saccharides- carbohydrates which yield a large no
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Eg- starch, cellulose,
glycogen, etc
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Reducing sugars- Those carbohydrates which reduce fehling’s solution and
tollen’s reagent
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Non reducing sugars- In disaccharides , if the reducing group of mono
saccharides ie, aldehydic or ketonic group are bonded
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Monosaccharides- If a monosaccharide contain an aldehyde group , it is known
as aldose
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Glucose- it present freely in nature as well as in the combined form
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Preparation of glucose
(1) From Sucrose ( disaccharide )- If sucrose is boiled with dil HCl / H2SO4 in
alcoholic solution, then glucose and fructose are obtained in equal amounts
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( C6H10O5)n + nH2O

nc6H12O6

Structure of glucose/Dextrose- An aldohexose
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Most abundant organic compound on
earth
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D represent the configuration
whereas (+) represents dextrorotatory nature of the molecule
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CHO
H

CHO
OH

CH2OH
(+) glyceraldehydes
D- Configuration

H

OH
CH2OH

(-) glyceraldehydes
L-Configuration

Cyclic structure of glucose- The open structure of the glucose explained
most of its properties but the following reactions could not be explained1
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2
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3
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The α- form ( m
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= 423K)
crystallised from concentrated solution of glucose at 303K
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This behaviour cannot be explained by the open structure of glucose
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Pyran is a cyclic organic compound
with one oxyzen atom and five carbon atoms in the ring
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it contain a ketonic functional
group at carbon no
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It belong to D – series and leavorotatory compound
Also written ad D(-) fructose
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The ring thus formed is a five membered ring and is
named as furanose with analogy to the compound furan
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Eg- sucrose,
maltose, lactose etc
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such a linkage between two
monosaccharides units through oxygen atom is called glycosidic linkage
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Mixture of glucose and fructose is
leavorotatory
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Maltose( disaccharides)- A reducing sugar
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Maltose composed of two α-D glucose units in which C1 of one glucose is linked
to C4 of another glucose unit
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Polysaccharides- polysaccharides contain a large no
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They act as food storage/
structural materials
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Polymer of α-glucose and
consists of two components amylose and amylopectin
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It is
long unbranched chain polymer of α-D(+) glucose
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It is
branched chain polymer of α-D glucose
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It is a straight
chain polysaccharides composed only of β- D- glucose
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It is
present in liver, muscles and brain
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Note- when
body needs glucose, enzymes break the glycogen down to glucose
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It is essential for life in both plants and animals
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Carbohydrates are used as storage molecules as starch in plants and
glycogen in animals
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They are found in bio-systems in combination with many proteins and lipids
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They provide raw materials for many important industries like textiles, paper
and breweries
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Two type -------(a) D
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A
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N
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( Ribonucleic acid)
They are also called polynucleotides
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Structure of nucleic acids-

(a) A nucleoside (b) A nucleotide
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Nucleotide- When nucleoside is linked to phosphoric acid at 5’ position of
sugar moiety, we get a nucleotide
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Note - Both RNA and DNA contain adenine, guanine and cytosine
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DNA structure- Double strand helix structure
Adenine forms hydrogen bonds with thymine whereas cytosine forms
hydrogen bonds with guanine
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Messenger RNA( m- RNA )
2
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Transfer RNA ( t- RNA )
Note- DNA – Reserve of gentic information but RNA not
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RNA- Proteins are synthesied by RNA molecules in the cells but DNA molecules
do not synthesised proteins but transfer coded message for the synthesis of
proteins in the cell

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