Download Organic Molecules

Chemistry of Life
Properties of Water
1
Molecule Structure & Function
Covalent bonds: Hold atoms in a
single molecule together
They provide…
Structure
Store (chemical potential)
energy
They are strong
2
Molecule Structure & Function
Hydrogen bonds: hold molecules
together
They provide...
Structure (cohesion & surface
tension)
They are weak
3
Water
• Composed of 1 oxygen
and 2 hydrogen atoms
(H2O)
• All living things depend on
water
Cells are 70-95% water
4
Water: H2O
-
+
+
Water
• All living things depend on
water
– Cells are 70-95% water
• Polar molecule
– Has a more negative region
(oxygen) and a more positive
region (hydrogen)
• Draw the Lewis dot
structure…
– polar-covalent bond causes
a bent shape
6
Water
• Opposites attract!!
• The more negative oxygen
and more positive
hydrogen regions of two
water molecules will attract
and stick together
• Hydrogen bonds result
from the partially polar
ends of different molecules
being attracted to each
other.
7
Water
• Hydrogen bonds: attractive forces between two or more
molecules, holding them together
8
Properties of Water
•
•
•
•
Cohesion
Adhesion
Temperature moderation
The solid form has a lower
density than the liquid
• The universal solvent
9
Properties of Water:
Cohesion
• Cohesion
– Water being attracted to itself
• Causes surface tension: a
skin on the surface of water
• Cohesion allows some small
bugs and particles to sit on
the surface of the water
• Picture source:
http://www.sciencedaily.com/videos/200
6/0710-robot_walks_on_water.htm
10
Properties of Water:
Adhesion
• Adhesion
– Water being attracted to
other molecules
• Causes water to stick to
substances
• Combination of cohesion
and adhesion pulls water
upward through plants
and tree trunks
11
Properties of Water:
Temperature Moderation
• Water requires a large
amount of energy to
raise its temperature
– It has to lose lots of
energy to cool down
• It has to gain lots of
energy to heat up
• Therefore, it is more
resistant to large
changes in temperature
– This is way large bodies of
water near us are so cool
12
Properties of Water
• Water boils at 100°C and freezes at 0°C at sea level
13
Properties of Water:
Density of Solid vs. Liquid
• Most substances
greatest density is in
their solid state
• Water is weird… its
solid (ice) has lower
density than the liquid
form (water)
• Allows life to survive
under frozen ponds
and lakes
14
Ice vs. Liquid Water
• Solid water expands due to stable hydrogen bonds,
becoming less dense than liquid water.
15
Water as solvent
• Able to dissolve other
substances
• Known as the “universal
solvent”
– Water is a good solvent
• Substance that dissolves
other substances (solutes)
• Some chemicals add H+
ions to the aqueous
solution (acids), while
others add OH- ions to the
solution (bases)
16
Acids, Bases, and pH
• Acids
– Add H+ ions to a
solution
– pH below 7
• Bases
– Add OH- ions to a
solution
– pH above 7
17
Organic Compounds
• Contain Carbon
• Carbohydrates
– Sugars and starches
• Lipids
– Fats and steroids
• Proteins
• Nucleic Acids
– DNA and RNA
18
Carbohydrates
• Made up of sugar molecules
– 1 carbon : 2 hydrogen : 1 oxygen
• Monosaccharides
– “Simple sugars”
– 1 sugar molecule (ex. glucose,
fructose)
• Disaccharides
– 2 sugars molecules (ex. sucrose)
• Polysaccharides
– “Complex carbohydrates”
– Long polymer chains of sugar
molecules (ex. starch, cellulose, and
glycogen)
19
Lipids
• Water-avoiding compounds
• Fats
– Glycerol with fatty acid tails
– Saturated
• Maximum number of hydrogen in tails
• Ex. lard and butter
– Unsaturated
• Double-bonded carbon atoms
• Ex. Fish and olive oil
• Steroids
– Four rings with attached functional groups
– Ex. Cholesterol and sex hormones
20
Proteins
• Chains of amino acids
• Responsible for almost all
day-to-day functioning of
organisms
– Form structures
– Act as signals
– Speed up chemical
reactions
• Enzymes
21
Nucleic Acids
• Chains of nucleotides
– Base, simple sugar, and
phosphate group
• DNA and RNA
22