Transcript Ch. 4 Carbon

Chapter 4: Carbon
Carbon
•
Overview: Carbon—The Backbone of Biological
Molecules
•
All living organisms are made up of chemicals based
mostly on the element carbon
•
Organic chemistry is the study of carbon compounds
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The Formation of Bonds with
Carbon
 Carbon has four valence electrons
 This allows it to form four covalent bonds
with a variety of atoms
Versatility of Carbon
•
The bonding versatility of carbon
•
Allows it to form many diverse molecules,
including carbon skeletons
Name and
Comments
Molecular Structural
Formula
Formula
H
(a) Methane
CH4
H C
H
H
(b) Ethane
H H
C2H6
H C C H
H H
(c) Ethene
(ethylene)
H
C2H4
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H
C C
H
H
Ball-andStick Model
SpaceFilling
Model
Common Bonding Partners of Carbon
•
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)
N
C
H
O
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Which of the structures in this figure is an impossible
covalently bonded molecule?
a. A
b. B
C
c. C
d. D
e. E
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Molecular Diversity Arising from Carbon Skeleton
Variation
• Carbon chains
•
Form the skeletons of most organic molecules
•
Vary in length and shape
(a) Length
H H
H C C H
H H
Ethane
H H H
H C C C H
H H H
Propane
H
H C H
H
H
H H H H
(b) Branching
H C C C C H
H C C C H
H H H
H H H H
2-methylpropane
Butane
(commonly called isobutane)
H H H H
H H H H
(c) Double bonds H
H C C C C H
C C C C H
H
H
H H
1-Butene
2-Butene
H
H
H
H
C
H
H
C C H
C H
(d) Rings
H C
C
H
H C
C
H
H
C
C
C
Cyclohexane
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Benzene
Hydrocarbons
 Hydrocarbons
 Are molecules consisting of only carbon and
hydrogen
 The bonds between the C and H atoms are non-polar
covalent
 This makes hydrocarbons hydrophobic
Hydrocarbons
•
Hydrocarbons
•
Are found in many of a cell’s organic
molecules
Fat droplets (stained red)
(a) A fat molecule
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100 µm
(b) Mammalian adipose cells
Isomers
 Isomers
 Are molecules with the same molecular formula
but different structures and properties
Isomers
•
Three types of isomers are
•
Structural
•
Geometric
•
Enantiomers
(a) Structural isomers
(b) Geometric isomers
H H H H H
H C C C C C H
H H H H H
X
C C
H
(c) Enantiomers
H
H C H
H C H
H
H
H C C C H
H H H
H
X
X
H
CO2H
C
H
CH3
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C C
X
H
CO2H
NH2NH2
C
CH3
H
Why are Enantiomeric isomers important?
•
Enzymes distinguish between enantiomers!
H
(a) Structural isomers
H
H
H
H
H
H
C
C
C
C
C
H
H
X
(b) Geometric isomers
H
H
H
H
H
H
Enzyme
X
activity
=
C
C
100 %
H
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C
C
C
NH2
CH3
C
CO2H
C
H
C
H
H
H
C
H
H
H
Enzyme
H
X
activity
=
C
C
X0 %
H
CO2H
(c) Enantiomers
H
H
H
H
NH2
CH3
H
Structure and Function
 Subtle changes in structure can dramatically
affect the molecule’s function
The Functional Groups
 Functional groups
 Are the chemically reactive groups of atoms
within an organic molecule
 They behave consistently and characteristically,
giving unique properties to the molecules
possessing them.
 Six functional groups are important in the
chemistry of life






Hydroxyl
Carbonyl
Carboxyl
Amino
Sulfhydryl
Phosphate
Functional Groups
FUNCTIONAL
GROUP
HYDROXYL
CARBONYL
CARBOXYL
O
OH
(may be written HO
C
C
OH
)
STRUCTURE 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.

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When an oxygen atom is doublebonded to a carbon atom that is
also bonded to a hydroxyl group,
the entire assembly of atoms is
called a carboxyl group (—
COOH).
Functional Groups
CARBONYL
HYDROXYL
NAME OF
COMPOUNDS
Alcohols (their specific
names usually end in -ol)
EXAMPLE
H
H
H
C
C
H
H
Ketones if the carbonyl group is Carboxylic acids, or organic
within a carbon skeleton
acids
Aldehydes if the carbonyl group
is at the end of the carbon
skeleton
H
OH
CARBOXYL
H
C
H
C
H
H
Ethanol, the alcohol
present in alcoholic
beverages
H
O
C
C
H
O
C
OH
H
H
Acetone, the simplest ketone
H
H
H
C
C
H
H
O
C
Propanal, an aldehyde
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H
Acetic acid, which gives vinegar
its sour tatste
Functional Groups
AMINO
SULFHYDRYL
H
O
SH
N
(may be written HS
H
The amino group (—NH2)
consists of a nitrogen atom
bonded to two hydrogen
atoms and to the carbon
skeleton.
PHOSPHATE
)
O P OH
OH
The sulfhydryl group
consists of a sulfur atom
bonded to an atom of
hydrogen; resembles a
hydroxyl group in shape.
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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 .
Functional Groups
H
O
C
HO
C
H
PHOSPHATE
SULFHYDRYL
AMINO
H
N
H
H
Glycine
H
H
C
C
H
H
OH OH H
SH
H
C
C
C
H
H
H
O
O
P
O
O
Ethanethiol
Because it also has a carboxyl
group, glycine is both an amine
and a carboxylic acid;
compounds with both groups
are called amino acids.
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Glycerol phosphate
Effect of Different Functional Groups
•
Functional groups give organic molecules
distinctive chemical properties
Estradiol
OH
CH3
HO
Female lion
OH
CH3
CH3
O
Male lion
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Testosterone
Key Points of Chapter 4
 Organic chemistry is the study of carbon
compounds
 Carbon atoms can form diverse molecules
by bonding to 4 other atoms
 Functional groups are the parts of molecules
involved in chemical reactions and behave
chemically in expected manners
Chapter 4 Essay Question
 Discuss the biological importance of each
of the following organic compounds in
relation to cellular structure and function in
plants and animals.




a. Carbohydrates
b. Proteins
c. Lipids
d. Nucleic acids