Chapter 4-Carbon & Diversity
of Life
Why carbon makes life diverse
Types of Isomers
Functional Groups and
Characteristics
Carbon and Diversity
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Carbon has four bonding sites
This allows for large and complex molecules to
be made with this element
They may form flat or tetrahedral molecules and
may also form rings, chains or branched
molecules
Carbon may also bond with itself as well as
other common elements like Nitrogen,
Hydrogen, and Oxygen
These possibilities make a wide variety of
organic molecules possible
Types of Isomers
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An isomer is a molecule that has the same
molecular formula as another molecule but
a different structure and thus different
properties.
There are a few different types of isomers:
Structural
Geometric
Enantiomers (Chiral carbons)
Structural Isomers
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Differ from one another in location of
double bonds and arrangement of atoms
Examples are butane and isobutane (see
page 56 )
Geometric Isomers
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Same covalent bonds but differ in
arrangement in space (spatial)
Example is rhodopsin
Rhodopsin changes from one geometric
isomer to another to allow sight in darker
places (Rods in your retina) and return to
vision in bright light
Enantiomers
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Mirror images of each other but not
superimposable due to an asymmetric
carbon
Important in pharmaceutical industry
Examples: L-Dopa and Thalidomide
Functional Groups
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Groups of atoms commonly part of carbon
skeletons that give certain properties to
organic molecules
There are a number of functional groups
given in your book (see chart on pg. 58)
The Hydroxyl Group
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-OH
Alcohols (names end in ol)
Example: Ethanol
Polar
Can form hydrogen bonds with sugars
which aids them in dissolving organic
compounds such as sugars
Carbonyl Group
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>CO
Form both Ketones (if it occurs within a carbon
skeleton) and Aldehydes(if it occurs at the end
of a carbon skeleton)
The simplest ketone is acetone
An aldehyde is Propanal
Both groups are found in sugars
Ketones form ketose sugars and aldehydes form
aldose sugars
May be strucural isomers as in acetone and
propanal
Carboxyl Group
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-COOH
Organic or carboxylic acids
Example: Acetic acid (vinegar)
Has acidic properties (donates hydrogen
ions) because the bond between hydrogen
and oxygen is so polar
Can be found in cells in ionized form (Ex:
Acetate ions)
Amino Group
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-NH2
Consists of a Nitrogen atom bonded to two
hydrogen atoms and then to a carbon skeleton
Known as amines
Examples are the amino acids like Glycine
Generally acts as a base by picking up H+ ions
from the surrounding solution (the aqueous
solution in living organisms)
Under cellular conditions it is usually in ionized
form. (1+)
Sulfhydryl Group
-SH
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Consists of a sulfur atom bonded to hydrogen
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Compounds referred to as Thiols
Example: the amino acid Cysteine
Two of these groups can form a covalent bond
and cross link to stabilize protein structure
These cross-links also determine the
straightness or curliness of hair
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Phosphate Group
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-PO3 2-
A phosphorus atom is bonded to four oxygen
atoms
One oxygen is bonded to the carbon skeleton
while two carry negative charges
Referred to as organic phosphates
Ex: Glycerol phosphate which is a backbone for
phospholipids which are the most prevalent
molecules in cell membranes
Can react with water to release energy
Contributes negative charge to the molecule that
contains it
Methyl Group
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-CH3
Consists of a carbon atom bonded to three
hydrogen atoms
Can be bonded to the carbon or a different atom
Referred to as Methylated Compounds
Addition of a methyl group to DNA effects gene
expression and arrangement of methyl groups in
sex hormones affects their shape and funtion
Ex: 5-Methyl cytidine (part of DNA that has been
modified by adding a methyl group