Biomolecules Formula Sheet — JEE Main Chemistry

Every key Biomolecules formula, definition and theorem for JEE Main Chemistry in one place — with common examiner traps and worked examples. Free to read; blurt from memory, then check your gaps.

Syllabus — topics coveredNTA · 11 sub-topics

General introduction and importance of biomolecules
Carbohydrates - Classification, aldoses and ketoses
Monosaccharides (glucose and fructose)
Constituent monosaccharides of oligosaccharides (sucrose, lactose, maltose)
Proteins - Elementary idea of alpha-amino acids, peptide bond, polypeptides
Proteins: primary, secondary, tertiary and quaternary structure
Denaturation of proteins, enzymes
Vitamins - Classification and functions
Nucleic Acids - Chemical constitution of DNA and RNA
Biological functions of nucleic acids
Hormones (General introduction)

Carbohydrates I — Classification, Glucose & Fructose

Carbohydrates: Optically active

polyhydroxy aldehydes or ketones

, or compounds that give them on hydrolysis (many fit

C_{x} (H_{2} O)_{y}

). Classified by hydrolysis into mono-, oligo- and poly-saccharides, and by behaviour into

reducing

vs non-reducing sugars.

Classifying carbohydrates

▸ $Monosaccharide$ : can't hydrolyse further — glucose, fructose, ribose.
▸ $Oligosaccharide$ : 2–10 units — sucrose, maltose, lactose.
▸ $Polysaccharide$ : many units — starch, cellulose, glycogen.
▸ $Reducing$ (reduce Tollens'/Fehling's) = all monosaccharides $+$ maltose, lactose; sucrose is non-reducing.

🎯 Exam · The six proofs of glucose's open chain

HI /Δ \to

n-hexane (6 C, straight).

N H_{2} OH

HCN

add

\Rightarrow

> C = O

B r_{2}

water

\to

gluconic acid

\Rightarrow

it is an

aldehyde

(C H_{3} CO)_{2} O \to

penta-acetate

\Rightarrow

5

- OH

HN O_{3} \to

saccharic acid

\Rightarrow

a primary

- C H_{2} OH

★ Remember · Glucose vs fructose

Glucose

= aldohexose,

D

(+)

(dextrose);

fructose

= ketohexose with the

> C = O

C_{2}

D

(-)

(laevorotatory). Both are

C_{6} H_{12} O_{6}

and both are reducing sugars.

⚠️ Watch out · D/L is configuration, not rotation

The

D

/L label fixes the spatial configuration (relative to glyceraldehyde, via the lowest asymmetric C); the

(+)

(-)

sign is the measured optical rotation. They are independent —

D

-glucose is

(+)

but

D

-fructose is

(-)

🚫 Examiner Trap · Examiner traps

(1) ALL monosaccharides are reducing; among disaccharides maltose/lactose reduce but

sucrose does NOT

(both anomeric C locked in the glycosidic bond). (2) Glucose's free

-

CHO is shown by B

r_{2}

-water (gluconic acid) — but it does NOT give the Schiff/2,4-DNP

+ N a H S O_{3}

tests fully (exists mostly cyclic). (3)

+ H N O_{3}

gives the di-acid (saccharic acid), confirming a terminal

- C H_{2}

OH. (4) Fructose is a keto-hexose yet still reduces Tollens (isomerises in base).

Carbohydrates II — Cyclic Sugars, Disaccharides & Polysaccharides

Cyclic ring forms: glucose as a 6-membered pyranose and fructose as a 5-membered furanose.

★ Remember · Why a ring, and what anomers are

The

C5

- OH

adds to the

C1

- CHO

to give a cyclic

hemiacetal

: glucose

\to

6-membered

pyranose

, fructose

\to

5-membered

furanose

. The

α

β

forms differ only at the new

C1

(

anomeric

carbon) — they are

anomers

🎯 Exam · Mutarotation explains the missing –CHO tests

In solution

α ⇌

open chain

⇌ β

(

mutarotation

), so very little free

- CHO

exists at any moment. That is why glucose fails the 2,4-DNP / Schiff /

NaHS O_{3}

tests despite being an aldose.

Sugar	Made of	Reducing?
Sucrose	α-glucose C1–C2 β-fructose	No (both anomeric C tied)
Maltose	two α-glucose, C1–C4	Yes
Lactose	β-galactose C1–C4 β-glucose	Yes (milk sugar)

★ Remember · Starch vs cellulose vs glycogen

Starch

= amylose (

α

-1,4 linear)

+

amylopectin (

α

-1,4

+

α

-1,6 branched) — plant storage.

Cellulose

β

-1,4 glucose, straight — plant structure.

Glycogen

= 'animal starch', more branched than amylopectin — liver/muscle.

🎯 Exam · Invert sugar

Sucrose is

(+)

, but hydrolysis gives glucose

(+ 52.5)

+

fructose

(- 92.4)

— net

(-)

. The sign flips, so the product is called

invert sugar

. The single

α

β

glycosidic bond ties up both reducing groups, making sucrose non-reducing.

🚫 Examiner Trap · Examiner traps

(1) Mutarotation:

α

and

β

anomers differ ONLY at the anomeric C1 and interconvert in solution. (2) Glucose pyranose

=

6-membered; fructose furanose

=

5-membered — don't swap them. (3) Starch

=

amylose (

α

-1,4 linear)

+

amylopectin (branched); cellulose

=

β

-1,4 (humans can't digest it). (4) Sucrose hydrolysis

\Rightarrow

'invert sugar' (rotation flips

+ \to -

because fructose is strongly laevorotatory).

Amino Acids — Structure, Zwitterion & Classification

α-Amino acid: A molecule with both an amino (

- N H_{2}

) and a carboxyl (

- COOH

) group on the

same

(

α

-) carbon, plus a side chain R. Proteins are polymers of

α

-amino acids — 20 of them build all natural proteins.

An alpha-amino acid in equilibrium with its dipolar zwitterion in water. — An $α$ -amino acid in equilibrium with its dipolar zwitterion in water.

★ Remember · The zwitterion makes them salt-like

In water both groups ionise to a dipolar

zwitterion

(

H_{3} N + - CHR - CO O^{-}

), which is

amphoteric

(reacts with acids and bases). That is why amino acids are high-melting, water-soluble crystalline solids — unlike simple amines or acids.

🎯 Exam · Isoelectric point

The

isoelectric point

is the pH at which the amino acid carries zero net charge (exists mainly as the zwitterion). Below it the

- CO O^{-}

picks up

H^{+}

(net

+

); above it the

- N H_{3}^{+}

loses

H^{+}

(net

-

Two classifications

▸ $Acidic$ (more $- COOH$ ): glutamic, aspartic acid.
▸ $Basic$ (more $- N H_{2}$ ): lysine, arginine.
▸ $Neutral$ (equal groups): glycine, alanine.
▸ $Essential$ (Val, Leu, Ile, Lys, Phe, Trp, Thr, Met, His, Arg) — diet-only; the rest are made in the body.

⚠️ Watch out · All are chiral except glycine

Every

α

-amino acid has a chiral

α

-carbon (four different groups) and is optically active —

except glycine

(R = H, so two H on the

α

-C). Most naturally occurring amino acids are the

L

-form.

🚫 Examiner Trap · Examiner traps

(1) Amino acids exist as

zwitterions

(internal salt)

\Rightarrow

high m.p., water-soluble, amphoteric — NOT as the neutral

- N H_{2}

-

COOH form. (2) At the

isoelectric point

net charge

= 0

and the molecule is least soluble / doesn't migrate in an electric field. (3) All standard amino acids are chiral (L-form) EXCEPT

glycine

=

H). (4) 'Essential' means must come from DIET (body can't synthesise) — not 'most important'.

Proteins — Peptide Bond, Structure Levels & Denaturation

The four levels of protein structure: primary, secondary, tertiary and quaternary.

★ Remember · Peptide bond

An amide

- CO - NH -

formed between the

- COOH

of one amino acid and the

- N H_{2}

of the next, with loss of

H_{2} O

. Chains grow dipeptide

\to

polypeptide; a

protein

has

>

100 residues (MW

>

10000 u; insulin = 51).

Four levels of structure

▸ $Primary$ : the exact sequence of amino acids.
▸ $Secondary$ : $α$ -helix (intramolecular H-bonds) & $β$ -pleated sheet.
▸ $Tertiary$ : overall 3-D folding (H-bonds, $S - S$ , van der Waals, ionic).
▸ $Quaternary$ : arrangement of two or more sub-unit chains.

🎯 Exam · Fibrous vs globular

Fibrous

: parallel chains held by H-bonds/disulphide,

insoluble

— keratin (hair, wool), myosin (muscle).

Globular

: chains coil into a sphere, usually

soluble

— insulin, albumins. The shape comes from the tertiary structure.

⚠️ Watch out · Denaturation keeps the primary structure

Heat or a pH change breaks the H-bonds, the helix uncoils, and the protein loses its biological activity — but only the

2^{\circ}

and

3^{\circ}

structures are destroyed; the

1^{\circ}

sequence stays intact. Examples: egg-white coagulation, milk curdling.

🚫 Examiner Trap · Examiner traps

(1) The peptide (amide) bond forms by losing

H_{2}

O between

-

COOH of one and

- N H_{2}

of the next. (2)

Denaturation

destroys

2^{\circ} / 3^{\circ}

structure (H-bonds/SS break) but the PRIMARY sequence (peptide bonds) stays intact — a common trap. (3)

α

-helix and

β

-pleated sheet are held by H-bonds (secondary). (4) Fibrous

=

structural/insoluble (keratin); globular

=

functional/soluble (enzymes, insulin).

Enzymes & Vitamins

Vitamin	Source	Deficiency disease
A (retinol)	fish-liver oil, carrots	xerophthalmia, night blindness
$B_{1}$ (thiamine)	yeast, cereals	beri-beri
$B_{2}$ (riboflavin)	milk, egg	cheilosis
$B_{6}$ (pyridoxine)	yeast, grams	convulsions
$B_{12}$	meat, fish, curd	pernicious anaemia
C (ascorbic acid)	citrus fruits, amla	scurvy (bleeding gums)
D	sunlight, fish, egg	rickets / osteomalacia
E	vegetable oils	RBC fragility, weakness
K	green leafy veg	raised clotting time

Enzymes

▸Almost all are $globular proteins$ ; highly specific to one substrate and reaction.
▸Named after the substrate $+$ ' $-ase$ ' (maltase, oxidoreductase).
▸They $lower the activation energy$ — sucrose hydrolysis $E_{a}$ drops from 6.22 to 2.15 kJ mo $l^{- 1}$ with sucrase.
▸Needed only in tiny amounts; they let life's reactions run under mild conditions.

★ Remember · Fat-soluble vs water-soluble vitamins

Fat-soluble

(A, D, E, K) are stored in liver/adipose tissue.

Water-soluble

(B-group and C) are excreted in urine, so they must be supplied regularly in the diet — the exception is

B_{12}

, which can be stored.

🎯 Exam · Deficiency diseases worth memorising

\to

night blindness/xerophthalmia;

B_{1} \to

beri-beri;

B_{2} \to

cheilosis;

B_{12} \to

pernicious anaemia; C

\to

scurvy; D

\to

rickets/osteomalacia; K

\to

slow blood clotting.

🚫 Examiner Trap · Examiner traps

(1) Enzymes LOWER the activation energy — they do NOT change

Δ G

or the equilibrium position. (2) Enzymes are highly specific (lock-and-key) and almost all are globular proteins. (3)

Fat-soluble vitamins (A, D, E, K) are STORED

\Rightarrow

overdose possible; water-soluble (B, C) are excreted

\Rightarrow

need daily supply. (4) Match deficiency: A

\to

night-blindness, B

_{1} \to

beri-beri, C

\to

scurvy, D

\to

rickets, K

\to

poor clotting.

Nucleic Acids — DNA, RNA & the Double Helix

Nucleic acids: Polynucleotides (DNA and RNA) that store and express heredity. Complete hydrolysis gives a

pentose sugar

phosphoric acid

and

nitrogen bases

. DNA uses 2-deoxyribose and bases A, G, C, T; RNA uses ribose and A, G, C, U.

The DNA double helix held by complementary base pairing (A=T, GequivC). — The DNA double helix held by complementary base pairing ( $A = T$ , $G \equiv C$ ).

Feature	DNA	RNA
Sugar	$β$ -D-2-deoxyribose	$β$ -D-ribose
Bases	A, G, C, $T$	A, G, C, $U$
Strands	double helix (Watson–Crick)	single (m-, r-, t-RNA)
Function	heredity, self-duplication	protein synthesis

Building blocks

▸ $Nucleoside$ = base $+$ sugar (base at $C 1^{'}$ ).
▸ $Nucleotide$ = nucleoside $+$ phosphate (at $C 5^{'}$ ).
▸Nucleotides link by $phosphodiester$ bonds ( $3^{'} \to 5^{'}$ ).
▸ $Purines$ A, G (double ring); $pyrimidines$ C, T, U (single ring).

★ Remember · The Watson–Crick double helix

Two complementary, antiparallel strands twist into a helix held by base pairing:

A = T

(two H-bonds) and

G \equiv C

(three H-bonds). The sugar–phosphate backbone forms the rails; the base pairs are the rungs.

🎯 Exam · DNA vs RNA

DNA

: deoxyribose, base

T

, double helix — stores heredity and self-duplicates.

RNA

: ribose, base

U

, single-stranded (m-, r-, t-RNA) — carries out protein synthesis. Base pairing is what lets DNA be copied faithfully.

🚫 Examiner Trap · Examiner traps

(1)

Nucleoside

=

base

+

sugar (NO phosphate);

nucleotide

=

nucleoside

+

phosphate — keep them distinct. (2) DNA sugar is 2-deoxyribose, RNA is ribose; DNA has Thymine, RNA has Uracil. (3) Base pairing A

=

T (2 H-bonds), G

\equiv

C (3 H-bonds) — purine always pairs with pyrimidine. (4) Backbone links are

phosphodiester

^{'} \to 5^{'}

); DNA is double-helix, RNA usually single-stranded.

Hormones & the Biomolecule Big Picture

Hormones: Chemical messengers secreted by endocrine glands that travel in the blood and regulate metabolism, growth and reproduction. They act at very low concentrations, and an imbalance causes disease (e.g. low insulin

\to

diabetes).

Three chemical classes of hormones

▸ $Steroid$ (from cholesterol): testosterone, estrogen, cortisol.
▸ $Amino-acid-derived$ : adrenaline (fight-or-flight), thyroxine (metabolic rate).
▸ $Peptide / protein$ : insulin & glucagon (blood-glucose control).
▸Imbalance $\Rightarrow$ disease: low thyroxine $\to$ hypothyroidism.

★ Remember · The four families at a glance

Carbohydrates

= energy/storage/structure;

proteins

= structure, enzymes, transport, hormones;

nucleic acids

= store & express genes (

DNA \to RNA \to

protein);

lipids/vitamins

= membranes, energy store, micro-cofactors.

🎯 Exam · How they connect

DNA's sequence (genes) is read by RNA to build

proteins

, many of which are

enzymes

that process

carbohydrates

and lipids for energy — and

vitamins

act as the small cofactors those enzymes need.

🚫 Examiner Trap · Examiner traps

(1) Hormones are released DIRECTLY into blood by ductless (endocrine) glands; they regulate, they are not catalysts (enzymes are). (2) Insulin/glucagon are PEPTIDE hormones; testosterone/estrogen/cortisol are STEROID (from cholesterol); adrenaline/thyroxine are amino-acid-derived. (3) Low insulin

\Rightarrow

diabetes; low thyroxine

\Rightarrow

hypothyroidism. (4) Don't confuse hormones (chemical messengers) with vitamins (micro-cofactors from diet).

More JEE Main Chemistry formula sheets

Frequently Asked Questions

What are the most important Biomolecules formulas for JEE Main?

This Biomolecules formula sheet covers all the high-yield Chemistry formulas, definitions and theorems you need for JEE Main, across General introduction and importance of biomolecules, Carbohydrates - Classification, aldoses and ketoses, Monosaccharides (glucose and fructose), Constituent monosaccharides of oligosaccharides (sucrose, lactose, maltose), Proteins - Elementary idea of alpha-amino acids, peptide bond, polypeptides — each shown with the key result and, where useful, a worked example.

Is this Biomolecules formula sheet free?

Yes — the full chapter formula sheet is free to read online, no login or payment required.

How should I revise Biomolecules formulas?

Blurt the Biomolecules formulas from memory, then check against this sheet to find your gaps — and practise a few previous-year questions on the chapter to make sure you can apply them under time pressure.

Also useful: all formula sheets · JEE Main previous-year papers · most important chapters.