AP BIO: Chapter 4 – Carbon and the
Molecular Diversity of Life
Lesson Presentation (notes)*** important to exam
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An overview of Carbon
Carbon – the backbone of life
o Isomers
o Functional Groups
Lesson Overview
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Cells are 70-95%water, the rest is mostly made up of carbon based compounds
Carbon is able to form large, complex and diverse molecules
Proteins and other molecules that distinguish living matter are composed of carbon compounds
4.1
Organic chemistry is the study of carbon compounds
Vitalism, the idea that organic compounds arise only in organisms, was disproved when chemists
synthesized these compounds
Mechanism is the view that all natural phenomena are governed by physical and chemical laws
4.2
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Carbon can form divers molecules by bonding to 4 other atoms
Electron cconfiguration*** determines the kinds of bonds
Carbon has 4 valenece electrons
Tetrahedral shape
When 2 carbon atoms are joined by a double bond it is flat shaped
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Most frequent partners/ combatable with are: hydrogen, oxygen and nitrogen
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Carbon chains form the skeletons for most organic molecules, they vary in length and shape…
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4.3
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A small # of chemical groups are key to the functioning of biological molecules
Properties of organic molecules depends on carbon skeleton and molecular components
attached to it
o Called functional groups
Functional groups – the components of organic molecules that are most commonly involved
in chemical reactions
The number and arrangement of these groups give each molecule its unique properties
7 functional groups important to life
o Hydroxyl group
o Carbonyl group
o Carboxyl group
o Amino group
o Sulfhydryl group
o Phosphate group
o Methyl group
Atp
o Phosphate molecule
o Adenosine triphosphate
o Energy transferring molecule in cells
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Isomers
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Isomers are compounds that have the same molecular formulas but different physical structures
Structural isomers
o Differ in the covalent partnerships between their atoms
Cis-trans isomers
o Vary an arrangement of atoms around a double bond
Enantiomers
o Molecules that are mere images of each other
Functional Groups
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Characteristics on an organic molecule depend on its carbon skeleton and the groups of atoms
attached to the skeleton that are involved in other chemical reactions
Phosphate group
Sulfhydryl group
Carbonyl group
Carboxyl group
Amino group
Book Notes
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Carbon: the backbone of life
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Organic Chemistry is the study of carbon compounds
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Molecular Diversity arising from Variation in Carbon Skeletons
o Carbon chains form skeletons of most organic molecules
o They vary in length and shape (see above figures)
o Carbon skeletons are the reason for the molecular complexity and diversity
o Hydrocarbons are attached to cells
Hydrocarbons- organic molecules consisting of only carbon and hydrogen
Isomers – variation in the architecture of organic molecules; the same chemical structure but
different physical structure
Structural Isomers – differ in the covalent arrangements of their atoms
4.1
4.2
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Cis-trans isomers – carbons have covalent bonds to the same atoms but these atoms differ in
spatial arrangements due to the inflexibility of double bonds
o Differ in arrangement about a double bond. X represents an atom or group of atoms
attached to a double-bonded carbon
o Cis isomer: the two Xs are on the same side
o Trans isomer: the two Xs are on opposite sides
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Enantiomers - Differ in spatial arrangement around an asymmetric carbon, resulting in
molecules that are mirror images, like left and right hands
o Due to the presence of an asymmetric carbon, one that is attached to four different
atoms or groups of atoms
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Usually only one isomer is biologically active because only that form can bind to specific
molecules in an organism
4.3
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Chemical Groups
o Properties of the chemical depend on the a arrangement of its carbon skeleton and the
chemical groups attached to the skeleton
Functional groups – chemical groups are directly involved in chemical reactions
o each has certain properties such as shape and charge
o Hydroxyl group
o Carbonyl group
o Carboxyl group
o Amino group
o Sulfhydryl group
o Phosphate group
o Methyl group
 First 6 can be chemically reactive
 Of these 6, all but sulfhydryl group are also hydrophilic
 Methyl group is not reactive
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Adenosine triphosphate (ATP) – a more complicated organic phosphate; used for energy in cells