Transcript c - kyoussef-mci

Chapter 4
Carbon and the
Molecular Diversity of
Life
1
Carbon Chemistry
• All living organisms are made up of chemicals
based mostly on the element carbon
Figure 4.1
2
Carbon Chemistry
• Organic chemistry is the study of carbon
compounds
• Carbon atoms can form diverse molecules
• Why?
• Carbon has 4 valence
electrons and may for
single, double, triple or
quadruple bonds
3
Name and
Comments
(a) Methane
Molecular
Formula
Structural
Formula
Ball-andStick Model
Space-Filling
Model
H
CH4
C
H
H
H
(b) Ethane
(c) Ethene
(ethylene)
C2H6
C2H4
H
H
H
H
H
C
C
H
H
C
C
H
H
H
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• The electron configuration of carbon gives it
covalent compatibility with many different
elements
Hydrogen
Oxygen
Nitrogen
Carbon
(valence = 1)
(valence = 2)
(valence = 3)
(valence = 4)
H
O
N
C
Figure 4.4
5
• Carbon may bond to itself forming carbon
chains
• Carbon chains form the skeletons of most
organic molecules
• Carbon chains vary in length and shape
H H H
H H
(a) Length
H
(b) Branching
H
(c) Double bonds
H
C C H
H H
Ethane
H
H
H H H H
C C C C
H H H H
Butane
H
H
C
H
C
H
H
(d) Rings
Figure 4.5 A-D
H
H
C
C
C
C
C
C
H
H
H
H
Cyclohexane
H
H
C C C
H H H
C
H
H H
H
H C C
H
1-Butene
H
H
H
H
H
C
H
isobutane
H H
C
H
C C C H
H H H
Propane
H H
C
C
H
H
2-Butene
H
H
C
C
C
C
C
Benzene
H
6
Hydrocarbons
• Hydrocarbons are molecules consisting of only
carbon and hydrogen
• Hydrocarbons are found in many of a cell’s organic
molecules
Fat droplets (stained red)
Figure 4.6 A, B
(a) A fat molecule
100 µm
(b) Mammalian adipose cells
7
Isomers
• Isomers are molecules with the same molecular
formula but different structures and properties
• Three types of isomers are
H
H C H
H C H
– Structural
H H H H H
H
H
H C C C C C H
H C C C H
H H H
H H H H H
– Geometric
H
X
X
X
C
C
C
C
– Enantiomers
X
(a) Structural isomers
(b) Geometric isomers
http://www.chemguide.co.uk/basicorg/isomerism/structural.html
http://www.chemguide.co.uk/basicorg/isomerism/geometric.html
http://www.chemguide.co.uk/basicorg/isomerism/optical.html
(c) Enantiomers
H
H
H
CO2H
H
C
CH3
CO2H
NH2 NH2
C
H
CH3
Figure 4.7 A-C
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• Enantiomers Are important in the
pharmaceutical industry
Figure 4.8
L-Dopa
D-Dopa
(effective against
Parkinson’s disease)
(biologically
inactive)
9
Functional Groups
• Functional groups are
the parts of
molecules involved in
chemical reactions
• They Are the
chemically reactive
groups of atoms
within an organic
molecule
• Give organic
molecules distinctive
chemical properties
Estradiol
HO
Female lion
OH
CH3
CH3
O
Figure 4.9
OH
CH3
Testosterone
Male lion
10
• Six functional groups are important in the chemistry of
life
–
–
–
–
–
–
Hydroxyl
Carbonyl
Carboxyl
Amino
Sulfhydryl
Phosphate
11
Some important functional groups of organic
compounds
FUNCTIONAL
GROUP
HYDROXYL
CARBONYL
O
OH
(may be written HO
STRUCTURE
Figure 4.10
CARBOXYL
C
C
OH
)
In a hydroxyl group (—
OH), a hydrogen atom is
bonded to an oxygen atom,
which in turn is bonded to
the carbon skeleton of the
organic molecule. (Do not
confuse this functional
group with the hydroxide
ion, OH–.)
O
The carbonyl group
( CO) consists of a
carbon atom joined to
an oxygen atom by a
double bond.

When an oxygen atom is
double-bonded to a carbon
atom that is also bonded to a
hydroxyl group, the entire
assembly of atoms is called a
carboxyl group (—COOH).
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Names of Compounds
NAME OF
COMPOUNDS
Alcohols (their specific
names usually end in -ol)
Ketones if the carbonyl group
is within a carbon skeleton
Aldehydes if the carbonyl
Carboxylic acids, or organic
acids
group is at the end of the
carbon skeleton
EXAMPLE
H
H
H
C
C
H
H
H
OH
H
Ethanol, the alcohol
present in alcoholic
beverages
H
C
H
C
H
H
Acetone, the simplest ketone
H
Figure 4.10
C
H
H
O
H
H
C
C
H
H
C
H
O
C
OH
Acetic acid, which gives vinegar
its sour tatste
O
C
H
Propanal, an aldehyde
13
Functional Groups
AMINO
SULFHYDRYL
H
N
H
The amino group (—NH2)
consists of a nitrogen
atom bonded to two
hydrogen atoms and to
the carbon skeleton.
Figure 4.10
PHOSPHATE
O
SH
(may be written HS
)
O
P OH
OH
The sulfhydryl group
consists of a sulfur atom
bonded to an atom of
hydrogen; resembles a
hydroxyl group in shape.
In a phosphate group, a
phosphorus atom is bonded to
four oxygen atoms; one oxygen is
bonded to the carbon skeleton;
two oxygens carry negative
charges; abbreviated P . The
phosphate group (—OPO32–) is an
ionized form of a phosphoric acid
group (—OPO3H2; note the two
hydrogens).
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Chemical Properties of
Functional Groups
• Functional groups possess certain chemical properties
that they impart to the molecules to which they are
attached.
Hydroxyl  Polar – hydrophilic
δ-
δ+
– Water molecules are attracted to hydroxyl group, dissolves
in water (e.g. sugars have hydroxyl groups)
Carboxyl  Polar – hydrophilic
– Carboxyl group is a source of hydrogen ions (H+) and
therefore makes the molecule acidic
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• Amino
– Act as a base, picking up protons (H+) from the surrounding
solution
• Sulfhydryl  Help stabilize structures of proteins
• Phosphate  Transfer of energy between organic
molecules (ATP)
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