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Types of Compounds
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Biology 102
Organic molecules
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Primary structure from carboncarbon-carbon bonds
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Most biological molecules
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Examples: carbohydrates, lipids, proteins
Lecture 2: Water
Types of Compounds
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Inorganic molecules
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Primary structure from anything except
carbon--carbon bonds
carbon
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Examples: NH3, O2, NaCl,
NaCl, CO2
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Most important for life is water
Properties of Water
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We are mostly water!
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All chemical processes for life occur in water
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Metabolism stops if cell’s water content drops
below 50%
Properties of Water
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Keys to water’s unique properties
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Shape
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Polarity and hydrogen bonds
Properties of Water
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Cohesion: the ability of molecules of a single
compound to stick together
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Water likes to stick to itself
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Due to hydrogen bonds
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Properties of Water
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Properties of Water
Adhesion: the ability of molecules of one
compound to stick to molecules of another
compound
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Water likes to stick to other molecules
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Due to hydrogen bonds
Water sticking to itself
Water sticking to
Something else
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Properties of Water
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The balance between these forces leads to all
kinds of phenomena
Properties of Water
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Properties of Water
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Surface tension
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Hydrogen bonds at the surface of water are
especially strong
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Reduces evaporation
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Acts as barrier (example: eyes)
The balance between these forces leads to all
kinds of phenomena
The balance between these forces leads to all
kinds of phenomena
Properties of Water
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Surface tension
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Properties of Water
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Surfactants are substances that disrupt surface
tension
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Properties of Water
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Lung surfactant
Examples: soap, egg yolk, EDTA, fabric
softeners, laxatives, insecticides
Properties of Water
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Specific heat
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Measure of how much thermal energy a
substance can absorb without changing
temperature
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How much heat it can store
Properties of Water
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Properties of Water
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Specific heat
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Specific heat
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Water has a VERY high specific heat – the
second highest found in nature
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Remarkable because of small mass
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Due to hydrogen bonds
Properties of Water
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Due to its high specific heat, water is excellent
for evaporative cooling
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ALL hydrogen bonds must be broken for water
to escape and become a gas
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Takes a tremendous amount of energy
Makes water a very efficient insulator
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Properties of Water
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Energy is supplied by the molecules underneath
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Leaves the substance cooler
Properties of Water
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Lubrication
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Water is virtually incompressible
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Molecules pass over each other easily
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Reduces friction
Properties of Water
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Nearly universal solvent
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This is quite unusual
Solutions
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A solution is a homogenous mixture of one or
more solutes dissolved into a solvent
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Solute: what is dissolved
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Solvent: what is doing the dissolving
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Aqueous solution: one in which the solvent is
water
Solubility
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Not all solutes will dissolve in all solvents
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Solubility rule of thumb: Like dissolves like
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Polar and ionic solutes dissolve in polar solvents
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Non--polar solutes dissolve in nonNon
non-polar solvents
Solvents and Solutes
Like dissolves like
Sugar (polar) +
Water (polar)
Sugar (polar) +
CCl4 (non
(non--polar)
Iodine (non(non-polar) +
Water (polar)
Iodine (non(non-polar) +
CCl4 (non
(non--polar)
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Solvents and Solutes
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Substances that associate with water =
hydrophilic (water
(water--loving)
Solvents and Solutes
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Substances that do not associate with water =
hydrophobic (water
(water--fearing)
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Polar or nonnon-polar?
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Polar or nonnon-polar?
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Examples?
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Examples?
Solvents and Solutes
Solvents and Solutes
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Substances that do not associate with water =
hydrophobic (water
(water--fearing)
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Some are both hydrophilic and hydrophobic at
the same time
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Non--polar
Non
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Surfactants
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Examples: oil, iodine, hydrophobic sand
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