### Biomolecules - Class 11
**Introduction to Biomolecules:**
- **Carbohydrates:** Sugars and starches, primary energy sources.
- **Monosaccharides:** Glucose, fructose.
- **Polysaccharides:** Starch, cellulose.
- **Proteins:** Made of amino acids, essential for body structure and functi...
• Water molecule
Water +ve H H
• Bipolar nature
• Chemical formula=H2O
O
• Hydrogen bond -ve
• Inorganic compound
Extra charge attracted &
• It is tasteless, odourless, colourless, yet 100% essential distribution gives over
all - tetrahedral pattern
• It is vital for all living organisms around O atom
• Essential for many activities of cell/life by acting as a solvent
in which all cell organelles and molecules are suspended
• H2O= One atom of Oxygen and two atoms of Hydrogen Structure of the water molecule. (a
nature of the H2O molecule is shown in a
model; the dashed lines represent th
• Mol wt: 18 (Atomic weights of two H atoms = 2, O = 16, Total=18) orbitals. There is a nearly tetrahedral
of the outer-shell electron pairs aroun
• Oxygen is highly electronegative. atom; the two hydrogen atoms have lo
positive charges (1) and the oxygen atom
• This causes the unequal distribution of electron sharing and negative charge (2). (b) Two H2O molecul
hydrogen bond (by three blue lines) betwe
neutrality of the bond because Oxygen pulls electrons towards itself atom of the upper molecule and a hydroge
lower one. Hydrogen bonds are longer an
and thus water becomes bipolar (one becomes +ve and the other becomescovalent O—H bonds.
-ve)
, • These influences
• Structure
• Self-assembly of itself (packing) and other molecules (Proteins, Nucleic acids, Polysaccharides etc)
• This property enables to dissolve polar solvents, other molecules through interactions at their interf
(through Hydrogen bonds (electrostatic attraction between oxygen of one water molecule to hydrogen
another water molecule, called Hydrogen bonds), other ionic interactions).
• It has high Boiling Point /Melting Point because of cohesive (packed) Hydrogen bonding within itself
Some biologically
hydrogen bonds.
• These Hydrogen bonds are relatively weak (90% electro static)
• Energy required to break H bonds of H20 to H and OH is: 23 KJ/mol
• Compared to
Common hydrogen bonds in biologi
• 470 KJ/mol of O-H (covalent bond) (>20times) Kj = Kilo joules
The hydrogen acceptor is usually oxyge
the hydrogen donor is another electroneg
See also next ppt
• 348 KJ / mol of C-C (covalent bond) (>15 times)
• The sum of all the hydrogen bonds between H20 molecules confer great internal cohesive (packed)
strength on liquid water.
, • Hydrogen bonds, also are formed between electronegative atom (Hydrogen acceptor) usually Oxygen /
Nitrogen) of any other molecules (not necessarily only water) and a hydrogen atom that is covalently
bonded another electronegative atom (hydrogen donor) in the same or another molecule.
• NOTE: Hydrogen atom covalently bonded to carbon atoms do not participate in hydrogen bonding,
because C atom is almost neutral (not electronegative).
• The strength of the Hydrogen bond depends upon its geometry or configuration of water or any other
molecule and varies from molecule to molecule.
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