PRESICE AND SHORT NOTES TO BE ABLE TO CRACK NEET EXAM COMING FROM AN MBBS STUDENT. CAN BE USEFUL IN BOARD EXAMS AS WELL. INFORMATION FROM AAKASH COACHING CENTRES AND NCERT TEXTBOOKS HAVE BEEN ADDED.
CH 9 Biomolecules
● Chemical composition and metabolic reaction in living org - similar
● Abundance of carbon, hydrogen and oxygen is higher in living systems than earth crust - water is
most abundant CHEMICAL in living organisms. O2 is the most abundant ELEMENT in living org.
● Biomolecules : all carbon compounds obtained from living tissues.
● Analysing :
○ Living tissue - grind with trichloroacetic acid in mortar and pestle - thick slurry - strain with
cheesecloth - 2 parts obtained
■ Filtrate - acid soluble pool - organic compound found - use separation techniques
isolate compounds - inorganic compounds (sulphate, phosphate) also seen
■ Retentate - acid insoluble fraction (nucleic acids, polysaccharides, proteins)
○ Inorganic elements : ASH ANALYSIS - destructive experiment - weigh living tissue and
dry it, water evaporates - dry weight obtained - if tissue burnt, carbon compounds oxidised
to gaseous forms (CO2, water vapour removed) - remaining ash contains inorganic elements
(Ca, Mg).
● Comparison study of elements: most abundant element in living tissue - oxygen (O2)
○ C,N,H,O,S - more in human body (O>C>N>H>S)
○ Ca,Mg,Na,Si - more in earth's crust (Si>Ca>Na>Mg)
○ Fe2+ and Cu2+ found in cytochromes
● Inorganic subs in living tissues: Na, K, Ca, Mg, H²O, Nacl, CacO3, Po4³-, SO4²- (K>Na>Ca)
● Biomolecules : micromolecules and macromolecules :
● Micromolecules : acid soluble - amino acids, simple sugars, nucleotides, LIPIDS (obtained in acid
insoluble fraction but weighs lesser than 800 daltons) - 18 to 800 daltons m.mass - cytoplasmic
composition without organelles.
● Macromolecules : acid insoluble - nucleic acids, proteins, polysaccharides - above 800 daltons -
macromolecules of cytoplasm and cell organelles.
● Average Composition of cell: H2O (70-90%) > Proteins(10-15%) > Nucleic acids(5-7%) >
Carbohydrates(3%) > Lipids(2%) >ions(1%)
● Primary and secondary metabolites :
○ Primary metabolites - identifiable function, perform primary physiological processes - In
animal cells - nucleotides, amino acids, carbohydrates, lipids, nitro bases - functions known
○ Secondary metabolites - no direct function - not involved in primary metabolism -
synthesised by plant, fungal, microbial cells - primary metabolites and secondary metabolites
(alkaloids, flavonoids, rubber, essential oils, antibiotics, pigments, scent, gums, spices) -
functions not fully known - useful in human welfare, ecological importance. Ex: cyanotoxins-
herbicides and insecticides
○ Carbohydrates: compounds of C,H,O - AKA saccharides - micromol and macromol.
● Micromol - 3 types - monosac, derived monosac, oligosaccharides and macro-polysac
○ Monosaccharides: can’t be hydrolyzed further - 3 to 7 C atoms - reducing sugars (have
free ald / ketone - can reduce Cu2+ to Cu+) - mannose, gluc, fruc, galac (hexoses) - white,
sweet, soluble in water - crystalline
■ Glucose : universal sugar - dextrose / grape sugar / corn sugar
■ Fructose : fruit sugar - levulose - sweetest among natural sugars
○ Derived monosaccharides:
, ■ Deoxy sugar : deoxygenation of ribose - deoxyribose (remove O at 2nd C) - in DNA
■ Amino sugar : glucosamine
■ Sugar acid : glucuronic acid, ascorbic acid
■ Sugar alcohol : Mannitol (present in brown algae)
○ Oligosaccharides: formed by condensation of 2-9 monosac, joined by glycosidic bonds -
usually btw 1st C and 4th C. Depending on no. of monosac combined : DISACH - sucrose,
maltose, lactose, trehalose (haemolymph of insects), TRISACH - Raffinose (gluc,fruc,galac),
TETRASACH - stachyose all reducing EXCEPT SUCROSE (glycosidic bond btw ald of gluc
and keto of fruc) AND TREHALOSE - benedict and fehling's test to detect presence of glu
in urine. (based on free keto / ald - reducing sugars)
● Macromol : Polysaccharides - chains of monosach - Right end is reducing and left end is non
reducing - cell wall in plants, fungi, exoskeleton of arthropods - energy stored as polysaccharides
(starch and glycogen) - considered macromolecules - acid insoluble pellet :
○ Homopolysaccharides: only one type of monosac monomer :
■ Glycogen - 30,000 gluc residues - branched structure - α 1,4 at unbranching and
α 1,6 branching - gives red colour with Iodine - stored as reserve food in the liver and
muscles of man.
■ Starch - polymer of gluc - storehouse of energy and reserve food in plants - has
secondary helix structure - holds iodine molecules in helical portion - starch is blue in
colour in iodine - made of amylose (unbranched - α 1,4 linkage btw glucose
molecules - helical, each turn - 6 gluc units) and amylopectin (branched - α 1,6
linkage - branches after 25 gluc units)
■ Cellulose - has beta glucose homopolymer - no complex helices, can't hold iodine -
makes up the plant cell wall and most abundant org compound in biosphere -
unbranched - found in cotton fibres, wood, paper.
■ Inulin - polymer of fructose - storage poly for roots and tubers of dahlia - not
metabolised in humans - readily filtered by kidney - used in testing of kidney func
■ Chitin - 2nd most abundant org. substance - complex nitrogen containing
polysaccharide [N-Acetyl glucosamine] - exoskeleton of arthropods.
○ Heteropolysaccharides: more than one type of monosac monomer
■ Peptidoglycan- Made up of N-Acetyl glucosamine and N-Acetyl muramic acid -
bacterial cell wall - lysozyme degrades it (hydrolysing glyc bond), kills bacteria
■ Hyaluronic acid- Made up of D-N-Acetylglucosamine and D-Glucuronic acid -
toughness and flexibility of tendons and cartilage.
■ Agar : mucopolysach - from red algae - used as culture medium in labs
■ Amino acids : organic comp - amino group and acid group on same (alpha)
carbon, called alpha amino acids - substituted methanes - 4 subst in 4 valency -
hydrogen, carboxyl, amino group and R group (diff amino acid diff r group) -
occurring in proteins (20 types only) :
● The R group can be : hydrogen (glycine), methyl group (alanine), hydroxy methyl - CH2OH (serine).
● Essential amino acids - humans cant synthesise - lysine, methionine, phenylalanine,
tryptophan, valine, isoleucine,leucine,threonine. [PVT TIM HALL]
● Semi essential amino acids - synthesised slowly - arginine and histidine.
● Non essential amino acids - synthesised, not needed in diet - alanine, cysteine, glutamate,
glycine, proline,etc. (G Pro C G Alan)
● Zwitterions- ionizable nature of NH² and COOH. Has both +ve and -ve charge.
○ At isoelectric point-exists as dipolar ion - Zwitterion
● Joined by Peptide bonds between nh2 and cooh group and loss of h20. Oligopeptides (few AA)
and polypeptide (many AA)
● Chemical and phys properties :
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