Water makes up about 60% of the human body and is essential for many bodily processes. It is highly polar, with hydrogen atoms sharing electrons unevenly with the oxygen atom. This polarity allows water to dissolve many other polar substances and act as a solvent in solutions like blood. Water's cohesive hydrogen bonding gives it high surface tension and allows it to carry out important functions like regulating body temperature and transporting nutrients and waste.

1. Biochemistry 1:
Water
ppt. by Robin D. Seamon

2. IMPORTANCE OF WATER
Without water, most of our bodily processes
would not work.
About 60% of our bodies are made up of water.
• 90% blood (plasma) is water
• Carries wastes out of the body (sweat, tears,
urine)
• Helps maintain body temperature homeostasis
(sweat)
Water is used in many of the biochemical
reactions within our cells.

3. H2O
CHEMISTRY REVIEW:
• Oxygen is in group 16,
therefore it has 6 valence
(outer) electrons.
• Hydrogen is in group 1 so
has 1 valence electron.
• (The STABLE number state
is to have 8 electrons in the
valence shell.)
• How many more does
oxygen need to be stable?
• 2 Hydrogen molecules
provide that: creating a very
strong, stable bond.
2 Hydrogen atoms
1 oxygen atom
Covalent bond:
sharing electrons

4. Polarity of water
Water is considered to be a polar substance
because one side of the molecule has a POSITVE
charge and one of side has a NEGATIVE charge.

5. Positive and negative particles attract one another:
Hydrogen bonds- bonds
of water pulling
together; not as strong
as other bonds

6. S T I C K I N G T O G E T H E R :
• Cohesion- force that holds molecules of a
material together
• Adhesion- force that holds different substances
together
Water drop and
water drop
Water drop and
paper
6

7. The cohesion of water creates surface tension.
• This bond is strong enough to hold small
insects.
• It is also how a water-needle compass works-
the needle floats on the surface tension as it
orients itself towards the Earth’s magnetic
North Pole.

8. D I S S O L V I N G
• Water is a solvent- it dissolves solutes of solids,
liquids & gases
• Solute- substance that dissolves
• Solution- mixture of solvent and solute
(EXAMPLES: blood, sweat, tears)
http://www.chem4kids.com/files/matter_
solution.html
8

9. W A T E R
• universal solvent- most substances will dissolve
in it
WHY?
• Polar- have two areas that have opposite
charges
9

10. 10
+ ions pull toward
negative side of water
molecule
Water surrounds charged particles and
pulls them apart
- ions pull toward
positive side of water
molecule
http://www.chemistryland.com/CHM107/Water/WaterTutorial.htm#
VIDEO: How polarity makes water behave strangely (4min)

11. 11
pH- power of Hydrogen
• The acid/base balance
• 7 is neutral
VIDEO: Strengths & Weaknesses of acids & bases (3:50)
VIDEO: Crash Course Chemistry#30 pH & pOH (11min)
 STRONGER baseSTRONGER acid 

12. Acids release hydrogen ions (H+) in water.
HCL  H+ + Cl-
Bases release hydroxide ions (OH-) in water.
NaOH  Na+ + OH-
Sodium
Hydroxide
Hydrogen
Chloride
Sodium
Chloride = salt
Neutral
solutions- have
same number of
H+ ions and OH-
ions.

13. 13
NEUTRAL
Solubility of heavy
metals
Algal blooms
More Hydrogen Less Hydrogen
HIGHER
TEMP.
pH

14. Buffer-
• Chemical substance that
neutralizes small amounts of
acids and bases
• Help maintain pH homeostasis
• Blood- good buffer
CC VIDEO #2 Water (10 min)