The Chemical Basis of Life

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Chapter 2 The Chemical Basis of Life
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Rattlebox Moth
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Pheromones
Pherein to transport Hormon to stimulate
Pheromones are chemical messages used to
communicate between two organisms
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Organisms are Composed of Matter
Matter has mass and takes up space.
Matter is made of elements.
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Elements

• Cannot be broken down any farther by common
  chemical means
• The purest form of a substance
• As of 2007, scientists recognize 117 different
  elements
• Only 94 occur naturally on earth
• The rest are man made and very unstable
• Elements with more than 82 protons are unstable
  and spontaneously decay

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Trace Elements
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Compounds

• Substance containing 2 or more elements in a
  fixed ratio
• More common in nature than pure elements
• Properties of compounds are very different then
  the individual elements that comprise them

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Compounds
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Hydrogen
Nitrogen
Oxygen
Carbon
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Atoms
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Isotopes
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Radioactive Tracers
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PET scaning
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PET scanning (cont.)
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PET scanning (cont.)
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PET scanning (cont.)
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Importance of Electrons
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Electron Shells
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3 types of bonds in chemistry

• Ionic (electron donating/receiving)
• Covalent (electron sharing)
• Hydrogen (held together by opposite charges)

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Ionic Bonding
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Ions result from ionic bonding
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Sodium chloride
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Covalent Bonding
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Non-Polar Covalent Bonding
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Polar Covalent Bonding
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Hydrogen Bonding
Hydrogen bond
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Liquid
Solid
Gas
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Cohesion
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Heat vs. Temperature
HEAT the amount of energy associated with the
movement of atoms and molecules in a body of
matter
TEMPERATURE measures the intensity of heat
(average speed of all the molecules in a body,
not the total).
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Solutions

• Uniform mixture of two substances
• Two components
• Solvent
• The dissolving agent
• For life, solvent is usually water and is called
  an aqueous solution
• Solute
• The substance that is dissolved

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H2O
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Acid Precipitation
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Chemical Reactions
CH4 2 O2 ? CO2 2 H2O