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Chapter 4
Carbon and the Molecular
Diversity of Life
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Organic Chemistry
• Although cells are 70–95% water, the rest
consists mostly of carbon-based compounds
• Carbon is unparalleled in its ability to form
large, complex, and diverse molecules
• Proteins, DNA, carbohydrates, and other
molecules that distinguish living matter are all
composed of carbon compounds
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Fig. 4-2
EXPERIMENT
“Atmosphere”
Water vapor
CH4
Electrode
Condenser
Cooled water
containing
organic
molecules
H2O
“sea”
Sample for
chemical analysis
Cold
water
Concept 4.2: Carbon atoms can form diverse
molecules by bonding to four other atoms
• Electron configuration is the key to an atom’s
characteristics
• Electron configuration determines the kinds
and number of bonds an atom will form with
other atoms
• With four valence electrons, carbon can form
four covalent bonds with a variety of atoms
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Valences
• Valence: Number of covalent bonds an atom
will usually form.
• Usually equal to the number of electrons
needed to complete the outermost shell.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 4-3
Name
(a) Methane
(b) Ethane
(c) Ethene
(ethylene)
Molecular
Formula
Structural
Formula
Ball-and-Stick
Model
Space-Filling
Model
Hydrocarbons
• Major components of petroleum.
• Many organic compounds have regions that
consist only of these.
– Ex. Fats have long hydrocarbon tails that are
nonpolar attached to a polar head.
• Store a relatively large amount of energy.
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Hydrocarbons
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The Role of Hydrocarbons in Fat: Triglycerides
•Black =
carbon
•Gray =
hydrogen
•Red =
oxygen
(A)Triglycerides are fat molecules consists of a headpiece and
3 hydrocarbon tails – the tails store energy and account for
the hydrophobic behavior of fats.
(B)Mammalian adipose cells stockpile fat molecules as a fuel
reserve.
Isomers
• Isomers are compounds with the same molecular
formula but different structures and therefore
different properties:
– Structural isomers
– Geometric isomers
– Enantiomers
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Structural Isomers
• Differ in the covalent arrangement of their atoms.
• May also differ in the location of double bonds.
–
As the carbon skeleton increases in size, the number of
possible isomers increases tremendously.
• Differ in covalent partners & possibly location of
double bonds: butane and isobutane
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Geometric Isomers
•
Have the same covalent partnerships, but differ in their spatial
arrangements.
•
Arise from the inflexibility of double bonds – will not allow the atoms
they join to rotate freely about the bond axis (unlike single bonds).
•
Differ in arrangement about a double bond.
•
This slight difference in shape can dramatically affect the biological
activity of the molecules.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Enantiomers
• Molecules that are mirror
images of each other.
• Usually, these “right-handed”
and “left-handed” versions of
the same molecule allow for
one to be biologically active
and the other inactive.
–
Ex. Thalidomide
• Differ in spatial arrangement
around an asymmetric carbon.
–
Results in molecules that are
mirror images, like left and right
hands.
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The Pharmacological Importance of Enantiomers
• Two enantiomers of a drug
may not be equally effective
(and in some cases, produce
harmful effects).
–
Thalidomide was prescribed for
pregnant women in the late
50’s – a drug that was a
mixture of two enantiomers.
•
One enantiomer reduced morning
sickness
•
The other caused severe birth
defects
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 4-8
Drug
Condition
Ibuprofen
Pain;
inflammation
Albuterol
Effective
Enantiomer
Ineffective
Enantiomer
S-Ibuprofen
R-Ibuprofen
R-Albuterol
S-Albuterol
Asthma
Fig. 4-7
Pentane
2-methyl butane
(a) Structural isomers
cis isomer: The two Xs are
on the same side.
(b) Geometric isomers
(c) Enantiomers
trans isomer: The two Xs are
on opposite sides.
Functional Groups
• Functional groups are the components of
organic molecules that are usually involved
in chemical reactions.
– Each group behaves consistently from one
organic molecule to another.
– The number and arrangement of functional
groups help give each molecule its unique
properties.
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Functional Groups
• The seven functional groups that are most
important in the chemistry of life:
– Hydroxyl group
– Carbonyl group
– Carboxyl group
– Amino group
– Sulfhydryl group
– Phosphate group
– Methyl group
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Text pg. 6465…KNOW
THE CHART!
A Comparison of Functional Groups
• Two molecules differ mainly in the attachment of functional groups
to a common carbon skeleton.
–
These subtle variations in molecular architecture (shaded in blue
and pink) influence the development of the anatomical and
physiological differences between female & male vertebrates.
–
Sexuality has a biological basis in variations of molecular
architecture!
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP: An Important Source of Energy for Cellular
Processes
• One phosphate molecule, adenosine
triphosphate (ATP), is the primary energytransferring molecule in the cell
• ATP consists of an organic molecule called
adenosine attached to a string of three
phosphate groups
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ATP: An Important Source of Energy for Cellular Processes
You should now be able to:
1. Explain how carbon’s electron configuration
explains its ability to form large, complex, diverse
organic molecules.
2. Distinguish among the three types of isomers:
structural, geometric, and enantiomer. Discuss
the biological importance of isomers.
3. Identify the 7 main functional groups and the
characteristics of each.
4. Explain how ATP functions as the primary energy
transfer molecule in living cells.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings