Download Carbon and the Molecular Diversity of Life

Carbon and the
Molecular Diversity of Life
Backbone of Biological Molecules
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Carbon is the backbone to life:
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Living organisms are made up of
chemicals based on element carbon
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Proteins, DNA, carbohydrates are
carbon-based
Source of biological carbon:
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Carbon enters biosphere through action
of photosynthetic plants, which uses
sun’s energy to convert CO2 into the
molecules of life
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Molecules are then passed through
ecosystem, often through feeding
relationships
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Carbon Bonds
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Molecular structure of carbon:
Mass number
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6 total electrons
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4 valence electrons (shell holds 8)
Rules of covalent bonding:
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Carbon forms covalent bonds with other
molecules (H, O, N)
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Number of valence electrons indicate how
many covalent bonds are formed for a
given element (subtract valence e- from
number of e- needed to complete shell)
Atomic number
12
6
C
C
Hydrogen
Oxygen
Nitrogen
Valence e- = 1
e- to complete shell = 1
# of bonds = 1
Valence e- = 6
e- to complete shell = 2
# of bonds = 2
Valence e- = 5
e- to complete shell = 3
# of bonds = 3
Distinctive Properties of
Organic Molecules
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Organic molecules:
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Consist mostly of “carbon” and “hydrogen” atoms
H
H
H
C
H
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From where do organic molecules get their distinctive properties?
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Molecular diversity – changes in the number of C-H (hydrocarbons) or changes in
orientation (isomers)
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Functional groups – component of organic molecule
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Molecular Diversity from Carbon
Hydrocarbons
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Hydrocarbons:
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Organic molecules consisting only of
carbon and hydrogen
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Hydrogen atoms attach to carbon
wherever electrons are available for
covalent bonding
Biological significance:
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Although rare in living organisms,
many of cell’s organic molecules
have regions consisting of only C and
H (e.g., tails of fat molecules)
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Undergo reactions that release a lot
of energy (gasoline of cars, fats that
fuel animal activity)
Why are fats so energy rich?
Hydrocarbon tails of fat serve as
stored fuel for animal bodies.
Molecular Diversity from Carbon
Hydrocarbons
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Molecular Diversity from Carbon
Isomers
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Isomers:
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Structural isomers:
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One of several organic compounds that have
same molecular formula but differ in covalent
arrangements of their atoms
Geometric isomers:
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Compounds that have same numbers of atoms
of same elements but different structures and
different properties
One of several organic compounds that have
same molecular formula but differ in spatial
arrangements of atoms around double bond
Enantiomers:
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Molecules that are mirror images of each other
Functional Groups
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Functional groups:
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Components of organic molecules
that are most commonly involved in
chemical reactions
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Functional groups often replace one
or more hydrogens bonded to carbon
skeleton of a hydrocarbon
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Functional groups give organic
molecules their unique properties
Six key functional groups:
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Hydroxyl
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Carbonyl
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Carboxyl
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Amino
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Sulfhydryl
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Phosphate
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Functional Groups
Hydroxyl
Potential to form hydrogen bonds
Functional Groups
Carbonyl
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Functional Groups
Carboxyl
Component of amino acids (building blocks of proteins)
and fatty acids (building blocks of some lipids)
Functional Groups
Amino
Component of amino acids
(building blocks of proteins)
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Functional Groups
Sulfhydryl
Disulfide bridges (S – S)
Functional Groups
Phosphate
Component of nucleotides (building blocks of nucleic acids)
and component of ATP (important for energy transfer)
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