Dear students, this PPT gives the detailed structure of water.

1. Structure of Water
Dr. K. GANESH KUMARI
ASSISTANT PROFESSOR
DEPARTMENT OF BOTANY
SRIMAD ANDAVAN ARTS AND SCIENCE COLLEGE
(AUTONOMOUS)
TRICHY - 5

2. Topics to be covered
• Introduction
• Forms of water
• Sources of water
• Water content of organisms
• Distribution of water in human body
• Structure of water molecule

3. Water - Introduction
• Water is the basic molecule of life.
• It is indispensable for life.
• None of the organisms known, can exist without water.
• It is astonishing to see that 70% of our earth is occupied by water
and in our body also about 70% of the total weight is water.
• The biological importance of water can be well understood by
the fact that life originated in the water medium.
• So water is aptly described as the mother of life or soul of life.
• Water is the most significant molecule which connects the
physical world with the biological processes.

4. Forms of Life
• Water exists in three forms, namely vapour
or steam, solid and liquid.
• Above 100ᴼC, it occurs in the form of
vapour or steam.
• Below 0ᴼC, it becomes solid called ice.
• Between 0ᴼC and 100ᴼC, it remains in the
liquid form.

5. Sources of Water
• Water is available to the biological system from a number of
sources such as seas, ponds, pools, lakes, rivers, streams,
springs, wells, precipitation etc.

6. Water content of Organisms
Age Total water %
Intracellular
water %
Outside the cells
Exatracellular
water %
Plasma %
New born 75 35 35 5
Under 1 year 70 35 30 5
From 1 to 10 years 60 – 65 35 – 40 20 – 25 5
From 10 to 50
years
55 – 60 40 – 45 15 5
Over 50 years 50 – 55 35 – 40 10 5

7. Water content of various tissues in human body
Tissue / Organ Water % Tissue / Organ Water %
Adipose tissue 10.0 Muscle 75.6
Osseous tissue 22.0 Spleen 75.8
Liver 68.3 Lung 79.0
Skin 72.0 Heart 79.2
Intestine 74.3 Kidney 82.7
Brain 74.8 Blood 83.0

8. Structure of water molecule
• Water is an inorganic compound.
• The molecular formula of water is
H2O.
• It contains 2 hydrogen atoms and
one oxygen atom.
• The hydrogen and oxygen atoms are
held together by covalent bonds
(bonds formed by the sharing of two
electrons)
• The three atoms in the water
molecule (2 hydrogen and 1 oxygen
atom) are not in a line.

9. Cont…
• But they are arranged in the form of a letter
“V”, with oxygen atom at the tip and the
hydrogen atoms at the ends of the two limbs.
• The bond angle between hydrogen and oxygen
atoms is 105ᴼ
• The central property of water molecule is its
electrical polarity.
• The oxygen atom is negatively charged and the
hydrogen atom is positively charged.
• As this molecule has two different poles like
that of a magnet, the water molecule is a
dipole.
• In other words water is polar compound

10. Cont…
• The polar molecules have the property of attracting
each other.
• Owing to this attractive force, water molecules
aggregate together.
• As a result of this force, a water molecule can link
with 4 adjacent water molecules.
• The linking between two water molecules is
effected by the formation of a hydrogen bond
(O……H) between the oxygen atom of one water
molecule and the hydrogen atom of another water
molecule.
• The oxygen atom forms a tetrahedron with the four
hydrogen atoms of the neighbouring 4 water
molecules.

11. Cont…
• Hydrogen bonds (O……H) are very weak
forces having only about 1/24th strength of
covalent bonds (O-H).
• The four water molecules are linked to a
water molecule by a 4 hydrogen bonds.
• These 4 hydrogen bonds are arranged
tetrahedrally and consequently the water
molecules in ice form a regular tetrahedral
crystalline structure.

12. Cont…
• As the hydrogen bonds are weak, any single hydrogen bond has
only an exceeding short life time.
• On a average each such bond last about 1/100 000 000th of a
second.
• So hydrogen bonds break and reform continuously.
• With increasing temperature, the bonds are increasingly broken.

13. Thank you