Chapter 4- carbon and
the molecular diversity
of life
Objective
• SWBAT explain the subcomponents of biological molecules and that their
sequences determine the properties of that molecule
Homework
1. Diagram pages 64 and 65. For all 7 chemical groups, include the structure,
name of compounds, examples, and list of functional properties.
2. Read Chapter 5 pp 68-85
Overview: Carbon: The Backbone of Life
Proteins
• Living organisms consist mostly
of carbon-based compounds
• Proteins, DNA, carbohydrates,
and other molecules that
distinguish living matter are all
composed of carbon
compounds
Carbohydrates
Lipids
Nucleic Acids
Organic Molecules and the Origin of Life on
Earth
• Stanley Miller’s classic
experiment demonstrated the
abiotic synthesis of organic
compounds
• Experiments support the idea
that abiotic synthesis of organic
compounds, perhaps near
volcanoes, could have been a
stage in the origin of life
Concept 4.2: Carbon atoms can form diverse
molecules by bonding to four other atoms
• Electron configuration is the
key to an atom’s characteristics
• Electron configuration
determines the kinds and
number of bonds an atom will
form with other atoms
The Formation of Bonds with Carbon
• With four valence electrons, carbon can form four
covalent bonds with a variety of atoms
• This ability makes large, complex molecules
possible
Figure 4.3
Name and
Comment
Molecular
Formula
(a) Methane
CH4
(b) Ethane
C2H6
(c) Ethene
(ethylene)
C2H4
Structural
Formula
Ball-andStick Model
Space-Filling
Model
• 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 CHON are bonded buddies
Covalent bond: type of strong chemical bond in
which two atoms share one or more pairs of
valence electrons
Valence: bonding capacity of a given atom; usually
equals # unpaired electrons req’d to complete
atom’s valence (outermost) shell
Figure 4.4
Hydrogen
(valence  1)
Oxygen
(valence  2)
Nitrogen
(valence  3)
Carbon
(valence  4)
Figure 4.UN01
Urea
Molecular Diversity Arising from Carbon
Skeleton Variation
• Carbon chains form the skeletons of most organic
molecules
• Carbon chains vary in length and shape
Animation: Carbon Skeletons
Right-click slide/select “Play”
Figure 4.5
(c) Double bond position
(a) Length
Ethane
Propane
(b) Branching
Butane
1-Butene
2-Butene
(d) Presence of rings
2-Methylpropane
(isobutane)
Cyclohexane
Benzene
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
Figure 4.6
Nucleus
Fat droplets
10 m
(a) Part of a human adipose cell
(b) A fat molecule
Isomers
• 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
• Enantiomers are isomers that are mirror images of
each other
Animation: Isomers
Right-click slide / select “Play”
Figure 4.7
(a) Structural isomers
(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
H
NH2
CH3
L isomer
NH2
H
CH3
D isomer
• 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
Figure 4.8
Drug
Condition
Ibuprofen
Pain;
inflammation
Albuterol
Effective
Enantiomer
Ineffective
Enantiomer
S-Ibuprofen
R-Ibuprofen
R-Albuterol
S-Albuterol
Asthma
The Miller-Urey experiment, shown
below,
a) showed that the conditions of
early Earth were inhospitable to
life
b) demonstrated that amino acids
and other organic molecules form
under conditions that may have
existed on Earth before life began
c) proved that life could originate
from inorganic chemicals
d) both B and C
The Miller-Urey experiment, shown
below,
a) showed that the conditions of
early Earth were inhospitable to
life
b) demonstrated that amino acids
and other organic molecules form
under conditions that may have
existed on Earth before life began
c) proved that life could originate
from inorganic chemicals
d) both B and C
Concept 4.3: A few chemical groups are key to the
functioning of biological molecules
• Distinctive properties of organic molecules depend
on the carbon skeleton and on the molecular
components attached to it
• A number of characteristic groups can replace the
hydrogens attached to skeletons of organic
molecules
The Chemical Groups Most Important in the
Processes 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
Figure 4.UN02
Estradiol
Testosterone
• The seven functional groups that are most important in
the chemistry of life: Need to know!!!!
•
•
•
•
•
•
•
Hydroxyl group
Carbonyl group
Carboxyl group
Amino group
Sulfhydryl group
Phosphate group
Methyl group
Functional Groups (Pg. 64 & 65)
• Seven groups to know and identify:
-Hydroxyl
(OH) Alcohols (not hydroxide)
-Carbonyl
(C=O) Aldehyde or Ketone
-Carboxyl
(COOH) weak acids
-Amino
(NH2) Proteins
-Methyl
(CH3)**Nonpolar hydrocarbon
-Phosphate (PO4) Nucleic acids: DNA & RNA
-Sulfhydryl (SH) Protein Structures
Figure 4.9-a
CHEMICAL
GROUP
Hydroxyl
Carbonyl
Carboxyl
STRUCTURE
(may be written HO—)
NAME OF
COMPOUND
Alcohols (Their specific names
usually end in -ol.)
Ketones if the carbonyl group is
within a carbon skeleton
Carboxylic acids, or organic acids
Aldehydes if the carbonyl group
is at the end of the carbon skeleton
EXAMPLE
Ethanol
Acetone
Acetic acid
Propanal
FUNCTIONAL
PROPERTIES
• Is polar as a result of the
electrons spending more time
near the electronegative oxygen
atom.
• Can form hydrogen bonds with
water molecules, helping dissolve
organic compounds such as
sugars.
• A ketone and an aldehyde may be
structural isomers with different
properties, as is the case for
acetone and propanal.
• Ketone and aldehyde groups are
also found in sugars, giving rise
to two major groups of sugars:
ketoses (containing ketone
groups) and aldoses (containing
aldehyde groups).
• Acts as an acid; can donate an
H+ because the covalent bond
between oxygen and hydrogen
is so polar:
Nonionized
Ionized
• Found in cells in the ionized form
with a charge of 1 and called a
carboxylate ion.
Figure 4.9-b
Amino
Sulfhydryl
Phosphate
Methyl
(may be
written HS—)
Amines
Organic phosphates
Thiols
Cysteine
Glycine
• Acts as a base; can
pick up an H+ from the
surrounding solution
(water, in living
organisms):
Nonionized
Ionized
• Found in cells in the
ionized form with a
charge of 1+.
Glycerol phosphate
• Two sulfhydryl groups can
react, forming a covalent
bond. This “cross-linking”
helps stabilize protein
structure.
• Contributes negative charge to
the molecule of which it is a part
(2– when at the end of a molecule,
as above; 1– when located
internally in a chain of
phosphates).
• Cross-linking of cysteines
in hair proteins maintains
the curliness or straightness
of hair. Straight hair can be
“permanently” curled by
shaping it around curlers
and then breaking and
re-forming the cross-linking
bonds.
• Molecules containing phosphate
groups have the potential to react
with water, releasing energy.
Methylated compounds
5-Methyl cytidine
• Addition of a methyl group
to DNA, or to molecules
bound to DNA, affects the
expression of genes.
• Arrangement of methyl
groups in male and female
sex hormones affects their
shape and function.
Is this molecule soluble in water?
a) yes
b) no
Is this molecule soluble in water?
a) yes
b) no
ATP: An Important Source of Energy for
Cellular Processes
• One phosphate molecule, adenosine triphosphate
(ATP), is the primary energy-transferring molecule in
the cell
• ATP consists of an organic molecule called adenosine
attached to a string of three phosphate groups
Figure 4. UN04
Adenosine
Figure 4. UN05
Reacts
with H2O
Adenosine
Adenosine
ATP
Inorganic
phosphate
ADP
Energy
What functional group is commonly used
in cells to transfer energy from one
organic molecule to another?
•a) carboxyl
•b) sulfhydryl
•c) hydroxyl
•d) phosphate
•e) amino
What functional group is commonly used
in cells to transfer energy from one
organic molecule to another?
•a) carboxyl
•b) sulfhydryl
•c) hydroxyl
•d) phosphate
•e) amino
Chapter 5- The Structure and
Function of Large Biological
Molecules
The four major macromolecules
1.
2.
3.
4.
Carbohydrates
Lipids
Proteins
Nucleic Acids
Macromolecules are large molecules
composed of thousands of covalently
connected atoms
Concept 5.1: Macromolecules are polymers,
built from monomers
• A polymer is a long molecule consisting of many similar building
blocks
• These small building-block molecules are called monomers
• Three of the four classes of life’s organic molecules are polymers
• Carbohydrates
• Proteins
• Nucleic acids
The Synthesis and Breakdown of
Polymers
• A dehydration reaction
occurs when two monomers
bond together through the loss
of a water molecule (lipids
exempt!!!)
• Polymers are disassembled to
monomers by hydrolysis, a
reaction that is essentially the
reverse of the dehydration
reaction
Animation: Polymers
Right-click slide / select “Play”
Figure 5.2
(a) Dehydration reaction: synthesizing a polymer
1
2
3
Short polymer
Unlinked monomer
Dehydration removes
a water molecule,
forming a new bond.
1
2
3
4
Longer polymer
(b) Hydrolysis: breaking down a polymer
1
2
3
Hydrolysis adds
a water molecule,
breaking a bond.
1
2
3
4
Concept 5.2: Carbohydrates serve as fuel
and building material
• Carbohydrates include sugars and the polymers of
sugars
• The simplest carbohydrates are monosaccharides,
or single sugars
• Carbohydrate macromolecules are
polysaccharides, polymers composed of many
sugar building blocks
Sugars
• Monosaccharides have molecular formulas that are
usually multiples of CH2O
• Glucose (C6H12O6) is the most common
monosaccharide
• Monosaccharides are classified by :
• The location of the carbonyl group (as aldose or
ketose)
• The number of carbons in the carbon skeleton
Figure 5.3
Aldoses (Aldehyde Sugars)
Ketoses (Ketone Sugars)
Trioses: 3-carbon sugars (C3H6O3)
Glyceraldehyde
Dihydroxyacetone
Pentoses: 5-carbon sugars (C5H10O5)
Ribose
Ribulose
Hexoses: 6-carbon sugars (C6H12O6)
Glucose
Galactose
Fructose
Figure 5.4
1
2
6
6
5
5
3
4
4
5
1
3
2
4
1
3
2
6
(a) Linear and ring forms
aqueous solutions many sugars form rings
• Monosaccharides serve as a major fuel for
cells and as raw material for building
molecules
6
5
4
1
3
• Though often drawn as linear skeletons, in
2
(b) Abbreviated ring structure
• A disaccharide is formed when a dehydration
reaction joins two monosaccharides
• This covalent bond is called a glycosidic linkage
Animation: Disaccharide
Right-click slide / select “Play”
Figure 5.5
1–4
glycosidic
1 linkage 4
Glucose
Glucose
Maltose
(a) Dehydration reaction in the synthesis of maltose
1–2
glycosidic
1 linkage 2
Glucose
Fructose
(b) Dehydration reaction in the synthesis of sucrose
Sucrose
Which group of large biological
molecules is not synthesized via
dehydration reactions?
a)
b)
c)
d)
polysaccharides
lipids
proteins
nucleic acids
Which group of large biological
molecules is not synthesized via
dehydration reactions?
a)
b)
c)
d)
polysaccharides
lipids
proteins
nucleic acids
Polysaccharides
• Polysaccharides, the polymers of sugars, have
storage and structural roles
• The structure and function of a polysaccharide are
determined by its sugar monomers and the positions
of glycosidic linkages
Storage Polysaccharides
• Starch, a storage polysaccharide of plants, consists
entirely of glucose monomers
• Plants store surplus starch as granules within chloroplasts
and other plastids
• The simplest form of starch is amylose
Figure 5.6
Chloroplast
Starch granules
Amylopectin
Amylose
(a) Starch:
1 m
a plant polysaccharide
Mitochondria
Glycogen granules
Glycogen
(b) Glycogen:
0.5 m
an animal polysaccharide
• Glycogen is a storage polysaccharide in animals
• Humans and other vertebrates store glycogen
mainly in liver and muscle cells
Figure 5.6b
Mitochondria
Glycogen granules
0.5 m
Structural Polysaccharides
• The polysaccharide cellulose is a major component
of the tough wall of plant cells
• Like starch, cellulose is a polymer of glucose, but the
glycosidic linkages differ
• The difference is based on two ring forms for glucose:
alpha () and beta ()
Animation: Polysaccharides
Right-click slide / select “Play”
Figure 5.7
(a)  and  glucose
ring structures
4
1
4
 Glucose
 Glucose
1 4
(b) Starch: 1–4 linkage of  glucose monomers
1
1 4
(c) Cellulose: 1–4 linkage of  glucose monomers
• Polymers with  glucose are helical
• Polymers with  glucose are straight
• In straight structures, H atoms on one strand can bond with OH
groups on other strands
• Parallel cellulose molecules held together this way are grouped into
microfibrils, which form strong building materials for plants
Figure 5.8
Cellulose
microfibrils in a
plant cell wall
Cell wall
Microfibril
10 m
0.5 m
Cellulose
molecules
 Glucose
monomer
• Enzymes that digest starch by hydrolyzing  linkages
can’t hydrolyze  linkages in cellulose
• Cellulose in human food passes through the digestive
tract as insoluble fiber
• Some microbes use enzymes to digest cellulose
• Many herbivores, from cows to termites, have
symbiotic relationships with these microbes
• Chitin, another structural polysaccharide, is found in
the exoskeleton of arthropods
• Chitin also provides structural support for the cell
walls of many fungi
Figure 5.9
The structure
of the chitin
monomer
Chitin forms the exoskeleton
of arthropods.
Chitin is used to make a strong and flexible
surgical thread that decomposes after the
wound or incision heals.
Figure 5.9a
Chitin forms the exoskeleton
of arthropods.
Figure 5.9b
Chitin is used to make a strong and flexible surgical
thread that decomposes after the wound or incision
heals.
Concept 5.3: Lipids are a diverse group
of hydrophobic molecules
• Lipids are the one class of large biological molecules
that do not form polymers
• The unifying feature of lipids is having little or no
affinity for water
• Lipids are hydrophobic because they consist mostly
of hydrocarbons, which form nonpolar covalent
bonds
• The most biologically important lipids are fats,
phospholipids, and steroids
Fats
• Fats are constructed from two types of smaller
molecules: glycerol and fatty acids
• Glycerol is a three-carbon alcohol with a hydroxyl
group attached to each carbon
• A fatty acid consists of a carboxyl group attached to a
long carbon skeleton
Figure 5.10
Fatty acid
(in this case, palmitic acid)
Glycerol
(a) One of three dehydration reactions in the synthesis of a fat
Ester linkage
(b) Fat molecule (triacylglycerol)
Figure 5.10a
Fatty acid
(in this case, palmitic acid)
Glycerol
(a) One of three dehydration reactions in the synthesis of a fat
• Fats separate from water because water molecules form hydrogen
bonds with each other and exclude the fats
• In a fat, three fatty acids are joined to glycerol by an ester linkage,
creating a triacylglycerol, or triglyceride
Figure 5.10b
Ester linkage
(b) Fat molecule (triacylglycerol)
• Fatty acids vary in length (number of carbons) and in
the number and locations of double bonds
• Saturated fatty acids have the maximum number of
hydrogen atoms possible and no double bonds
• Unsaturated fatty acids have one or more double
bonds
Animation: Fats
Right-click slide / select “Play”
Figure 5.11
(a) Saturated fat
Structural
formula of a
saturated fat
molecule
Space-filling
model of stearic
acid, a saturated
fatty acid
(b) Unsaturated fat
Structural
formula of an
unsaturated fat
molecule
Space-filling model
of oleic acid, an
unsaturated fatty
acid
Cis double bond
causes bending.
Figure 5.11a
(a) Saturated fat
Structural
formula of a
saturated fat
molecule
Space-filling
model of stearic
acid, a saturated
fatty acid
Figure 5.11b
(b) Unsaturated fat
Structural
formula of an
unsaturated fat
molecule
Space-filling model
of oleic acid, an
unsaturated fatty
acid
Cis double bond
causes bending.
Figure 5.11c
Figure 5.11d
• Fats made from saturated fatty acids are called
saturated fats, and are solid at room temperature
• Most animal fats are saturated
• Fats made from unsaturated fatty acids are called
unsaturated fats or oils, and are liquid at room
temperature
• Plant fats and fish fats are usually unsaturated
• A diet rich in saturated fats may contribute to
cardiovascular disease through plaque deposits
• Hydrogenation is the process of converting
unsaturated fats to saturated fats by adding hydrogen
• Hydrogenating vegetable oils also creates unsaturated
fats with trans double bonds
• These trans fats may contribute more than saturated
fats to cardiovascular disease
• Certain unsaturated fatty acids are not synthesized in
the human body
• These must be supplied in the diet
• These essential fatty acids include the omega-3 fatty
acids, required for normal growth, and thought to
provide protection against cardiovascular disease
• The major function of fats is energy storage
• Humans and other mammals store their fat in adipose
cells
• Adipose tissue also cushions vital organs and insulates
the body
Phospholipids
• In a phospholipid, two fatty acids and a phosphate
group are attached to glycerol
• The two fatty acid tails are hydrophobic, but the
phosphate group and its attachments form a
hydrophilic head
Hydrophobic tails
Hydrophilic head
Figure 5.12
Choline
Phosphate
Glycerol
Fatty acids
Hydrophilic
head
Hydrophobic
tails
(a) Structural formula
(b) Space-filling model
(c) Phospholipid symbol
Hydrophobic tails
Hydrophilic head
Figure 5.12a
(a) Structural formula
Choline
Phosphate
Glycerol
Fatty acids
(b) Space-filling model
• When phospholipids are added to water, they selfassemble into a bilayer, with the hydrophobic tails
pointing toward the interior
• The structure of phospholipids results in a bilayer
arrangement found in cell membranes
• Phospholipids are the major component of all cell
membranes
Figure 5.13
Hydrophilic
head
Hydrophobic
tail
WATER
WATER
Steroids
• Steroids are lipids characterized by a carbon skeleton
consisting of four fused rings
• Cholesterol, an important steroid, is a component in
animal cell membranes
• Although cholesterol is essential in animals, high levels
in the blood may contribute to cardiovascular disease
Figure 5.14
Concept 5.4: Proteins include a diversity of
structures, resulting in a wide range of
functions
• Proteins account for more than 50% of the dry mass of
most cells
• Protein functions include structural support, storage,
transport, cellular communications, movement, and
defense against foreign substances