Transcript 2.2 Water Notes Student

Chemistry of Life
Essential elements and water
Elements of living things
• Every living thing is
made of
– atoms are the smallest
part of an element
– Atoms of different
elements group
together to form
– If an atom loses or gains
an electron it becomes
charged =
– 99% of living matter consists of four elements
– Carbohydrates: carbon, oxygen, hydrogen
– Lipids: carbon, oxygen, hydrogen
– Proteins: consist of amino acids that contain carbon, oxygen,
hydrogen and nitrogen
Roles of essential elements
Element
Plants
Animals
Prokaryotes
• In some amino acids • In some amino acids •
• Trace elements
also existandinproteins
the body
and proteins
Sulphur
Calcium
•
•
Cell wall formation
between dividing
plants
Co-factor for certain
enzymes
•
•
•
In bone
Reacts in muscle
fiber contraction
Cofactor for certain
enzymes
•
•
In some amino acids
and proteins
Helps with heat
resistance in of
bacterial endospores
Co-factor in certain
enzymes
Phosphorus
•
Phosphate groups in
ATP
Phosphate groups in
ATP
Phosphate groups in
ATP
Iron
•
In cytochromes –
electron transport
molecule
•
In cytochromes and
hemoglobin
In cytochromes
Sodium
•
Sodium potassium
•
pump – part of
transporting
•
molecules across the
cell membrane
Sodium potassium
pump –
Sending nerve
impulses
•
Sodium potassium
pump to transport
molecules
Water is an important molecule for life
• Plants = 65 – 95% water
• Animals = 80% water
Water Molecule
• Unique structure that
gives water some
interesting
characteristics
• Consists of two hydrogen
atoms and one oxygen
atom
• – they share valence
electrons
• Hydrogen atoms
spend most of their
time around
• Hydrogen atoms are
offset giving one
side of the molecule
a slight charge and
the other side the
opposite charge – it
is a
molecule
*Annotate the diagram to show which
end is positive and negative
• Water forms hydrogen bonds –
an attraction to other positive
and negative charges
– Weak bond
*Hydrogen bonds give water
unique properties
Thermal Properties
• Water has high specific heat
– A lot of heat energy is needed to
raise the temperature of water
• Temperature is the measure of how
quickly molecules are moving in a
substance
• Hydrogen bonds must be broken
before water molecules can move
faster
• Lakes and ponds don’t change
temperature quickly
• Hydrogen bonds keep water
from vaporizing
Evaporation and
(evaporating) easily
Heat Loss
– When organisms evaporate
water (transpiration or
sweating), heat energy is
transferred to the water
molecule and carried off in
water vapor, cooling the
organism
Heat Energy and Freezing
• A lot of heat energy must be removed from
water to turn it to ice
• Water in the environment and in cells are
Density of Ice
• Ice is less dense than water: different from all other
materials
– Insulates freezing lakes and allows life to thrive under the
surface in freezing temps.
Cohesive and Adhesive Properties
• Cohesion: water
sticks to itself
through hydrogen
bonds
– Responsible for
surface tension
• Adhesion: water sticks to other charged
surfaces through
• Water can climb narrow tubes necessary to
bring water to the uppermost limbs of
plants
Solvent Properties
• Water is a powerful
solvent of polar
substances
– Ionic substances like
sodium chloride (Na+Cl-)
– Organic molecules (carbon
containing molecules that
are found in living things)
that have ionized
(charged) groups
Transparency
• Water is transparent
• Light can penetrate
water allowing aquatic
photosynthetic plants