Chemical Basis of Life
Chemistry
• Matter is made up of separate chemical
components.
– Chemistry = Interactions between atoms/molecules.
• Biological function begins at the chemical level.
– Hierarchical interactions add function.
– Ex. Photosynthesis
Sub-cellular concepts
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Matter
Elements
Atoms
Natural elements
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92
About 25 essential for life
H,O,N,C = 96% of human body
Trace elements
Periodic Table of Elements
Atomic Structure
• 3 Basic subatomic particles.
– Proton
– Electron
– Neutrons
• Atomic Number
• Atomic Mass
• Compounds
Isotopes
• Atoms representing different forms of the
same element.
• Same number of Protons, but different mass
– Different number of neutrons
• Radioactive Isotopes
Electrons
• Arranged
in shells
• Valence
• Reactivity
• Molecules
Molecular Structure
• Structural formula
• Ball and stick
Chemical Bonding – Ionic Bonds
• Form between Ions of opposite charge
• NaCl
– One atom gives up e- (cation).
– One atom recieves e- (anion).
– Results in filled outer shells for both.
Chemical Bonding – Ionic Bonds
Chemical Bonding – Covalent Bonds
• Result from electron sharing.
– 1 or more pairs of outer shell electrons.
– Number of possible bonds = number
needed to fill outer shell.
Chemical Bonding – Hydrogen
Bonds
• Attraction between the (+)
and (-) ends of a water
molecule
• Weak bonds
• Hydrogen = positive end
• Oxygen = negative end
Water
• Polar molecule
– Electronegativity
– Polar covalent bonds
• Cohesion
• Adhesion
• Resistant to
temperature change
More Definitions
• Solutions
– Solvent
– Solute
• Aqueous solution = Water is the solvent
– Water = Universal solvent
– Results from the Polarity
pH
• Potential hydrogen.
• H2O dissociates into H+ and OH- (hydroxide)
ions.
– Acids
– Bases
• pH scale
pH Scale
Chemical Reactions
• Processes producing chemical changes in
matter.
– Reactants
– Products
• Matter cannot be created or destroyed
• Energy flow
Types of Chemical Reactions
• Synthesis
– Ex. A + B => AB
• Decomposition
– Ex. AB => A + B
• Exchange
– Ex. AB + CD => AC + BD
• Oxidation-Reduction (redox)
– Ex. C6H12O6 + 6O2  6CO2 + 6 H2O + ATP