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CAMPBELL
BIOLOGY
Outline
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
4
I. Organic compounds
II. Bonding with Carbon
III. Isomers
IV. Functional Groups
Carbon and
the Molecular
Diversity of
Life
Dr Burns
NVC
© 2014 Pearson Education, Inc.
Organic Compounds
 What is organic
 We think of organic produce
 “natural”
 In chemistry organic refers to molecules that
have a carbon backbone, covalently bound to
each other
 Early chemists thought of organic as coming
from plants and animals and inorganic coming
from minerals
Overview: Carbon: The Backbone of Life
 Living organisms consist 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
© 2011 Pearson Education, Inc.
Figure 4.1a
Carbon
 Carbon has four valence
electrons. It needs eight
electrons to be stable
 So, carbon can form up to four
covalent bonds.
Carbon can bond to four other atoms or
groups of atoms, making a large variety of
molecules possible.
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Carbon compounds
Molecule
 Carbons can link together to form a backbone
– many other elements can bond to this
backbone
(a) Methane
 Carbon – carbon bonds are strong
(b) Ethane
Molecular
Formula
Structural
Formula
Ball-and-Stick Model
Space-Filling
Model
CH4
C2H6
 Carbons can form single, double or triple
bonds.
(c) Ethene
(ethylene)
 Carbons can form chains or rings
C2H4
Figure 4.5
Hydrocarbons
 Hydrocarbons are organic molecules
consisting of only carbon and hydrogen
(c) Double bond position
(a) Length
Ethane
Propane
(b) Branching
1-Butene
2-Butene
 Many organic molecules, such as fats, have
hydrocarbon components
(d) Presence of rings
 Hydrocarbons can undergo reactions that
release a large amount of energy
2-Methylpropane
(isobutane)
Butane
Cyclohexane
Figure 4.6
Benzene
Isomers
Nucleus
Fat droplets
 Isomers are compounds with the same
molecular formula but different structures and
properties
 Structural isomers have different covalent
arrangements of their atoms
 Cis-trans isomers have the same covalent
bonds but differ in spatial arrangements
10 μm
(a) Part of a human adipose cell
(b) A fat molecule
 Enantiomers are isomers that are mirror
images
of each other
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Animation: Isomers
(a) Structural isomers
Pentane
2-methyl butane
(b) Cis-trans isomers
cis isomer: The two Xs are
on the same side.
trans isomer: The two Xs are
on opposite sides.
(c) Enantiomers
CO2H
CO2H
C
H
C
NH2
NH2
H
CH3
L isomer
CH3
D isomer
Structural Isomers
 Molecule have different arrangement of their
carbon skeleton but still have the same
molecular formula:
Enantiomers
Cis-trans Isomers
 Have the same arrangement of atoms but the
spatial arrangement of the atoms are different.
 An example is cis vs trans arrangements across a
double bond (cis = large groups are on same
side, trans = large groups on opposite side
Enantiomers
 Isomers that are mirror
images of each other
 Must be a chiral molecule –
where a carbon is bonded
to four different molecules
 Referred to as:
 + or –
 R or L
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Why do we care
Why do we care
 The function of a protein is determined by its
shape.
 Biological organisms usually synthesize only one
form.
 Usually only one form of an isomer is active in
biological systems.
 However, chemical synthesis usually produces
equal amounts of the two enantiomers
 Enantiomers are important in the pharmaceutical
industry
 Two enantiomers of a drug may have different
effects
 Usually only one isomer is biologically active
 Differing effects of enantiomers demonstrate that
organisms are sensitive to even subtle variations
in molecules
Animation: L-Dopa
Right-click slide / select “Play”
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Figure 4.8
Drug
Condition
Ibuprofen
Pain;
inflammation
Albuterol
Effective
Enantiomer
Ineffective
Enantiomer
S-Ibuprofen
R-Ibuprofen
R-Albuterol
S-Albuterol
 Example: The drug albuterol (e.g., Proventil®)
contains equal amounts of two enantiomers.
 Another more expensive drug is levalbuterol
(Xopenex®) it only contains the active form of
the drug, it has fewer side effects
Asthma
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Functional Groups
This is an example of what kind of isomer?
Cis-trans
Enantiomers
Structural
None of the above
25% 25% 25% 25%
 Functional groups are the components of
organic molecules that are most commonly
involved in chemical reactions
e
ab
ov
ur
a
th
e
St
ru
ct
tio
m
er
s
an
eo
N
on
e
of
En
G
l
 The number and arrangement of functional
groups give each molecule its unique properties
m
et
ric
1.
2.
3.
4.
© 2011 Pearson Education, Inc.
Functional Groups
 Groups of atoms; determines the types of
chemical reactions and associations
Estradiol
Testosterone
1.
2.
3.
4.
5.
6.
7.
Polarity
Hydroxyl
Carbonyl
Carboxyl
Amino
Sulfhydryl
Phosphate
Methyl
Chemical Group
Hydroxyl group (—OH)
Compound Name
Examples
Alcohol
Ethanol
Carbonyl group (
 Remember that C-H and C-C bonds are
non polar
C＝O)
Ketone
Aldehyde
Acetone
Carboxyl group (—COOH)
Carboxylic acid, or
organic acid
Amino group (—NH2)
Amine
Sulfhydryl group (—SH)
Thiol
Phosphate group (—OPO32−)
Organic
phosphate
Methyl group (—CH3)
Methylated
compound
Propanal
Acetic acid
 S, N, and O are electronegative atoms and
can make a molecule more polar.
Glycine
Cysteine
 Polar and ionic functional groups are
hydrophilic, and strongly associate with
water
Glycerol phosphate
5-Methyl cytosine
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Properties of functional Groups
1. Hydroxyl – polar, can form hydrogen bonds
2. Carbonyl – polar, can form hydrogen bonds
3. Carboxyl – very polar, weakly acidic and can ionize
to become -COO- + H+

Important in amino acids
5. Sulfhydryl – also called thiol, polar, important in
proteins, can form strong S-S bonds that stabilize
structure
6. Phosphate – polar and weakly acidic. Can
dissociate to –PO4-2

4. Amino - Polar and weakly basic, can accept a H+ to
become –NH3+

Properties of functional Groups
Important in nucleic acids and some lipids
7. Methyl – nonpolar hydrocarbon
Important in amino acids and nucleic acids
Figure 4.9aa
Figure 4.9ab
Carbonyl group (
Hydroxyl group (—OH)
C＝O)
Ethanol, the alcohol
present
in alcoholic
beverages
(may be written HO—)
Polar due to electronegative oxygen. Forms hydrogen bonds with water.
Compound name: Alcohol
Figure 4.9ac
Acetone,
the simplest ketone
Propanal,
an aldehyde
Sugars with ketone groups are called ketoses; those with aldehydes
are called aldoses.
Compound name: Ketone or aldehyde
Figure 4.9ad
Carboxyl group (—COOH)
Amino group (—NH2)
Acetic acid, which
gives vinegar its
sour taste
Acts as an acid.
Compound name: Carboxylic acid, or organic acid
Ionized form of —COOH
(carboxylate ion),
found in cells
Glycine, an amino acid
(note its carboxyl group)
Ionized form
of —NH2,
found in cells
Acts as a base.
Compound name: Amine
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Figure 4.9ba
Figure 4.9bb
Sulfhydryl group (—SH)
Phosphate group (—OPO32−)
Glycerol phosphate,
which takes part in
many important
chemical reactions in
cells
Cysteine, a sulfurcontaining amino acid
(may be written HS—)
Two —SH groups can react, forming a “cross-link” that helps stabilize
protein structure.
Compound name: Thiol
Figure 4.9bc
Contributes negative charge. When attached, confers on a molecule the ability
to react with water, releasing energy.
Compound name: Organic phosphate
Carboxyl functional groups are:
Methyl group (—CH3)
5-Methyl cytosine, a
component of DNA
that has been modified
by addition of a methyl
group
1.
2.
3.
4.
Polar
Acidic
Nonpolar
Polar and acidic
25% 25% 25% 25%
ic
c
ac
id
po
la
r
ci
di
an
d
on
Po
la
r
N
A
Po
la
r
Affects the expression of genes. Affects the shape and function of
sex hormones.
Compound name: Methylated compound
Important Concepts
 Read Chapters 5 for next lecture
 Know the vocabulary of the lecture
 Understand the importance of carbon in organic
molecules
 What are the different types of isomers? Be able to
identify examples of each type of isomer.
 What are the structure and the properties of the
common functional groups?
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