1. Chapter 4
Carbon
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2. Overview: Carbon—The Backbone of Biological Molecules
Carbon can form large, complex, and diverse molecules, including “biological macromolecules”
Proteins, DNA, carbohydrates, lipids, and other molecules that distinguish living matter are all composed of carbon compounds

3. LE 4-4
Carbon
(valence = 4)

4. The Formation of Bonds with Carbon
With four valence electrons, carbon can form four covalent bonds with a variety of atoms
This tetravalence makes large, complex molecules possible

5. In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape
However, when two carbon atoms are joined by a double bond, the molecule has a flat shape

6. Molecular Formula Structural Formula Ball-and-Stick Model
Space-Filling
Model
Methane
Ethane
Ethene (ethylene)

7. The electron configuration of carbon gives it covalent compatibility with many different elements
The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living molecules

8. LE 4-4
Hydrogen
(valence = 1)
Oxygen
(valence = 2)
Nitrogen
(valence = 3)
Carbon
(valence = 4)

9. Molecular Diversity Arising from Carbon Skeleton Variation
Carbon chains form the skeletons of most organic molecules
Carbon chains vary in length and shape

10. Concept 4.3: Functional groups are the parts of molecules involved in chemical reactions
Distinctive properties of organic molecules depend not only on the carbon skeleton but also on the molecular components attached to it
Certain groups of atoms are often attached to skeletons of organic molecules

11. The Functional Groups Most Important in the Chemistry of Life
Functional groups are the components of organic molecules that are most commonly involved in chemical reactions
The number and arrangement of functional groups give each molecule its unique properties

12. The six functional groups that are most important in the chemistry of life:

13. Hydroxyl group - O - H NAME OF COMPOUNDS
Alcohols (their specific names
usually end in -ol)
FUNCTIONAL PROPERTIES
Is polar as a result of the
electronegative oxygen atom
drawing electrons toward itself.
Ethanol, the alcohol present in
alcoholic beverages
Attracts water molecules, helping
dissolve organic compounds such
as sugars (see Figure 5.3).

14. Ketones if the carbonyl group is
LE 4-10ab
STRUCTURE
EXAMPLE
Acetone, the simplest ketone
NAME OF COMPOUNDS
Ketones if the carbonyl group is
within a carbon skeleton
Propanal, an aldehyde
Aldehydes if the carbonyl group is
at the end of the carbon skeleton
FUNCTIONAL PROPERTIES
A ketone and an aldehyde may
be structural isomers with
different properties, as is the case
for acetone and propanal.

15. Carboxyl
NAME OF COMPOUNDS
Carboxylic acids, or organic acids

16. Acetic acid Carboxyl The covalent bond between
oxygen and hydrogen is so polar
that hydrogen ions (H+) tend to
dissociate reversibly;
In cells, found in the ionic form,
which is called a carboxylate group.
FUNCTIONAL PROPERTIES
Has acidic properties because it is
a source of hydrogen ions.
Acetic acid
Acetate ion

17. Amino Glycine Because it also has a carboxyl
NAME OF COMPOUNDS
Amine
Because it also has a carboxyl
group, glycine is both an amine and
a carboxylic acid; compounds with
both groups are called amino acids.

18. Sulfhydryl Ethanethiol FUNCTIONAL PROPERTIES
NAME OF COMPOUNDS
Thiols
FUNCTIONAL PROPERTIES
Two sulfhydryl groups can
interact to help stabilize protein
structure (see Figure 5.20).

19. Phosphate (ATP) FUNCTIONAL PROPERTIES NAME OF COMPOUNDS
Glycerol phosphate
NAME OF COMPOUNDS
FUNCTIONAL PROPERTIES
Organic phosphates
Makes the molecule of which it
is a part an anion (negatively
charged ion).
Can transfer energy between
organic molecules.
(ATP)

20. The Chemical Elements of Life: A Review
The versatility of carbon makes possible the great diversity of organic molecules
Variation at the molecular level lies at the foundation of all biological diversity

21. Length
Propane
Ethane

22. (commonly called isobutane)
Branching
2-methylpropane
(commonly called isobutane)
Butane

23. Double bonds
1-Butene
2-Butene

24. Rings
Cyclohexane
Benzene

25. Hydrocarbons
Hydrocarbons are organic molecules consisting of only carbon and hydrogen
Many organic molecules, such as fats, have hydrocarbon components
Hydrocarbons can undergo reactions that release a large amount of energy

26. Isomers
Isomers are compounds with the same molecular formula but different structures and properties:
Structural isomers have different covalent arrangements of their atoms
Geometric isomers have the same covalent arrangements but differ in spatial arrangements
Enantiomers are isomers that are mirror images of each other

27. Structural isomers differ in covalent partners, as shown in this example of two isomers of pentane.

28. cis isomer: The two Xs
are on the same side.
trans isomer: The two Xs
are on opposite sides.
Geometric isomers differ in arrangement about a double bond. In these diagrams, X represents an atom or group of atoms attached to a double-bonded carbon.

29. L isomer
D isomer
Enantiomers differ in spatial arrangement around an asymmetric carbon, resulting in molecules that are mirror images, like left and right hands. The two isomers are designated the L and D isomers from the Latin for left and right (levo and dextro). Enantiomers cannot be superimposed on each other.

30. Enantiomers are important in the pharmaceutical industry
Two enantiomers of a drug may have different effects
Differing effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules

31. (effective against Parkinson’s disease) (biologically Inactive) L-Dopa
LE 4-8
L-Dopa
(effective against
Parkinson’s disease)
D-Dopa
(biologically
Inactive)