ZLGY-MM: XI 9.

BIOMOLECULES
Biomolecules: Carbon compounds present in living systems.
II. Phospholipids are lipids with phosphorus compounds
BIOMICROMOLECULES E.g. Lecithin (found in cell membrane)
 Biomolecules having molecular weight less than 1000 Da are
called micromolecules.
1. Amino acids
 Amino acid are organic compound containing an amino group
(-NH2), an acid group (-COOH), H & a variable group (R)
attached to a C- atom (Cα).
 There are 20 amino acids used as building blocks for protein III. Sterols. e.g.: Cholesterol
synthesis.
E.g. -

Classification - 3. Sugars/ Saccharide

E.g.:
A. Based on requirement by animals, amino acids are 2 types:
o Essential amino acids (should get through diet)
o Non-essential amino acids (body can synthesize)

B. Based on the no. of amino & carboxyl group

Type Example
Acidic Glutamic acid
Basic Lysine 4. Nucleotides
Neutral Valine A nucleotide has 3 components:
1. A nitrogenous base- heterocyclic compound, 2 types -
 Amino acid, at a particular pH, possessing both NH3+ (cationic)
Purines: It includes Adenine and Guanine.
& COO- (anionic) is termed as zwitter ionic (zwitterGerman= both).
Pyrimidines: It includes Cytosine, Thymine & Uracil.
2. A pentose sugar (ribose in RNA & deoxyribose in DNA)
3. A phosphate group

zwitter ion N-glycosidic linkage ester linkage

2. Lipids  Nitrogen base + Sugar = Nucleoside + phosphate = Nucleotide

 Lipids are fatty acids esterified with various alcohols. Adenine + ’’ = Adenosine + ’’ = Adenylic acid
Classification - Guanine + ’’ = Guanosine + ’’ = Guanylic acid
A. Based on melting point, lipids are 2 types: fats and oils. Cytosine + ’’ = Cytidine + ’’ = Cytidylic acid
Thymine + ’’ = Thymidine + ’’ = Thymidylic acid
Fats- Solid @ room temp. (↑ mp) Uracil + ’’ = Uridine + ’’ = Uridylic acid
Lipids
(Triglycerides) Oils- Liquid @ room temp. (↓ mp)
B. Based on composition, lipids are 3 types-
I. The simple lipids are formed of alcohol like glycerol and fatty acids
 Glycerol is trihydroxy propane.

 Fatty acid are organic acids with hydrocarbon chain ending in a

carboxyl group (–COOH).
Eg: Palmitic acid-16 C, Arachidonic acid- 20 C
It includes monoglycerides= glycerol + 1 fatty acid
diglycerides = glycerol + 2 fatty acids
triglycerides = glycerol + 3 fatty acids

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 BIOMACROMOLECULES METABOLITES
 Biomolecules having molecular weight greater than 1000  Metabolites are the organic compounds taking part in metabolism.
Dalton (Da) is called macromolecules. They are 2 types:-
METABOLITES
1. Proteins /Polypeptides
 They are heteropolymers of amino acids linked by peptide bonds.
Functions of protein: Primary metabolites: Secondary metabolites: Compounds
Compounds present in other than primary metabolites, present in
organisms with known plants, fungi or microbes, which have no
role in normal known physiological role
physiology E.g.
E.g.
amino acids
sugars

 Most abundant protein in animal world: Collagen

 Most abundant protein in the biosphere: RuBisCO

Structure of protein
4 levels of protein structure can be recognised:
1. Primary structure: Here, the amino acids are linked with each ENZYMES
other to form a thread-like structure.  Enzymes are proteins which catalyse biochemical reactions in
2. Secondary structure: A protein thread is folded in the form of the cells (biological catalysts).
a right-handed helix.
3. Tertiary structure: Long protein chain is folded upon itself.
Structure of Enzyme
 Enzymes are made-up of 30 proteins.
4. Quaternary structure: Protein that are an assembly of more
Exception: Sometimes RNA act as enzymes called Ribozymes.
than one polypeptide or subunits.
E.g. Hb has 4 subunits (2 α and 2 βsubunits)  The 30 structure of an enzyme has some pockets called ‘active
site’ into which the substrate fits.

ENZYMES

Simple Enzyme Holoenzyme

Made up of only Made-up of protein +
proteins Non-protein part

Protein part Non-protein part

(Apoenzyme) (Co-factor)

Prosthetic group: Co-enzymes: Organic. Metal ions: Form

Organic. Permenantly Bound to apoenzyme co-ordination bonds
bound to apoenzyme. only during the time of with active site and
E.g. Haem in peroxidase catalysis. the substrate.
and catalase. E.g. Niacin in NAD and E.g. Zn in
NADP Carboxypeptidase.
2. Carbohydrates /Polysaccharides
 These are polymers of monosaccharides linked by glycosidic Enzyme action (Catalytic Cycle)
bond.
E.g: Starch, Cellulose, Glycogen, Chitin

3. Nucleic Acids /Polynucleotide

 Nucleic acids are heteropolymer of nucleotides.
2 types:
- DNA (deoxyribonucleic acid): contains deoxyribose sugar
- RNA (ribonucleic acid): contains ribose sugar.

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 Mechanism of Acceleration (Concept of Activation Energy) b) pH
In a reaction, the substrate has to go through a much higher  Optimum pH: pH at which particular enzymes show highest
energy state. It is called transition state energy. activity.
 Activation energy is the difference between average energy of
substrate and transition state (ES) energy.
 Role of enzyme: In a biochemical reaction, enzymes lower
the activation energy. As a result, speed of the reaction
increases.

Enzyme activity declines below and above optimum pH.

c) Concentration of substrate
Velocity of enzyme action rises with the increase in substrate
concentration
↓
Reaches a maximum velocity (Vmax)
↓
Velocity does not exceeded by further rise in concentration.
Reason: Enzyme molecules are fully saturated. i.e., no active
site is left free to bind with additional substrate molecules.
Factors affecting enzyme activity
a) Temperature
 Optimum temperature: Temperature at which particular enzymes
show highest activity.
Activity declines below and above optimum value.
o At low temperature: Enzyme temporarily inactive.
o At high temperature: Enzymes get denatured by heat.

Classification of Enzymes
Class Type of reaction catalysed Exemplified Reaction
1. Oxidoreductases/ Reaction involving the exchange of H2 atom or
S red + S’ ox S ox + S’red
dehydrogenases ion between two substrates
Transfer of a group (other than H) between a
2. Transferases S – G + S’ S + S’– G
pair of substrate S and S’
Hydrolysis of ester, ether, peptide, glycosidic, C-
3. Hydrolases S + H2O X+ Y
C, C-halide or P-N bonds.
Removal of groups from substrates by X Y
4. Lyases mechanisms other than hydrolysis leaving X-Y + C=C
double bond. C C
The rearrangement of molecular structure to
5. Isomerases X Y
form isomer.
The linking together of 2 compounds of C-O, C-S,
6. Ligases X + Y X–Y
C-N, P-O etc. bonds.

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