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The Molecules of Cells
Got Lactose?
◦ Many people in the world suffer from lactose
intolerance
 Lacking an enzyme that digests lactose,
a sugar found in milk
◦ Lactose intolerance illustrates the importance of
biological molecules

To the functioning of living cells and to human
health
3.1 Life’s molecular diversity is based on the
properties of carbon
◦ A carbon atom can form four covalent bonds
 Allowing it to build large and diverse
organic compounds
Structural
formula
Ball-and-stick
model
H
H
C
Space-filling
model
H
H
H
Methane
C
H
H
H
The 4 single bonds of carbon point to the corners of a tetrahedron.
Figure 3.1A

Organic Compounds
◦ Carbon Based Molecules
◦ All Carbon Atoms have four places in which other
atoms can bond

A molecule composed of only Carbon and
hydrogen.
◦ NON-POLAR MOLECULES


Carbon Skeleton – hydrocarbons bonded
together in a long chain.
Isomer – a compound with the same formula
but a different structure.
◦ Carbon chains vary in many ways
◦
http://bioweb.wku.edu/courses/BIOL115/Wyatt/
H
H
C C
H
H H
H
H
H
C C C
H
H H H
H H
Ethane
Propane
Carbon skeletons vary in length.
H
H
H H H H
H C C C C
C
H
H
H
H
H C C C
H
H H H
H H H
Butane
Isobutane
Skeletons may be unbranched or branched.
H
H H H
H
H H H H
H C C C C
H
H C C C C
H
H H
H
H
1-Butene
2-Butene
Skeletons may have double bonds, which can vary in location.
H
H
C
H
H
C
H C
H
C
C
H
C
H
H
H
H
H
H
H
H
C
C
C
C H
C
C
H
Benzene
Cyclohexane
Skeletons may be arranged in rings.
Figure 3.1A
H
◦ Functional groups are particular groupings of atoms
 That give organic molecules particular
properties
OH
Estradiol
HO
Female lion
OH
O
Figure 3.2
Male lion
Testosterone
A functional group is a group of atoms that
usually participate in chemical reactions.
5 Functional groups include:
Hydroxly Group - OH
Carbonyly Group C=O
Carboxyl Group COOH
Amino Group NH2
Phosphate –OPO32-

Hydroxly Group - OH
◦ Carbon chains with OH group form alcohols

C=O group forms
◦ Ketones
◦ Aldyheydes

COOH Groud form:
◦ Carboxylic Acids
◦ Acts as an acid by contributing H+ to solution and
becoming ionized (takes on a charge).
◦ Example – Acetic Acid (aka Vinegar)

NH2 Groups are known as amines.
◦ Form Amino acids ( the building blocks of proteins)
 a.a. are a combination of the amine group NH2 and
Carboxyl Group COOH.

OPO32- Usually bound to a carbon skeleton
by the Oxygen – this functional groups is
involved with energy production (ATP)
3.2 Functional groups help determine the
properties of organic compounds
◦ Examples of functional groups
Table 3.2
◦ The four main classes of Macromolecules are:




Carbohydrates
Lipids
Proteins
nucleic acids

Macromolecules
◦ Large molecules

Polymers
◦ Cells make most of their molecules by joining
organic molecules into chains.

Monomers
◦ The unit that serves as the building blocks of
poymers
Proteins are nothing more than amino acids
strung together.
Carbohydrates are sugars strung together.
Lipids (fats) are glycerol chains bound to fatty
acids
Nucleic Acids are a series of four different
bases (A, G, C, & T) arranged into a double
helix.
◦ Cells make most of their large molecules
 By joining smaller organic molecules
into chains called polymers
◦ Cells link monomers to form polymers
 By a dehydration reaction
H
OH
OH
OH
Short polymer
Unlinked monomer
Dehydration
Dehydratio
reaction
n reaction
H2O
OH
O
H
H
H
Longer polymer
Figure 3.3A
H
H
◦ Polymers are broken down to monomers by the
reverse process:
 HYDROLYSIS
H2O
H
OH
Hydrolysis
H
OH
OH
Figure 3.3B
H

How many molecules of water are needed to
completely break down a polymer that is 50
monomers long?

How many molecules of water are needed to
completely break down a polymer that is 50
monomers long?
 49



Re-read 3.1 – 3.3 and fill in notes.
Complete Chapter Objective 3.1 – 3.3
Prepare for quiz 3.1 – 3.3
◦ On-Line Book Support Activities 3A – 3C
◦ Key Concept Quiz

Read 3.4 – 3.7 Carbohydrates
The term carbohydrates refers to a class of
molecules that range from:
small sugar molecules (sugar in soft drinks)
To
large polysaccharides (starch molecules in
potatoes/pasta)
 Are monosaccharides
Figure 3.4A

Monomers:
◦ Single unit sugar
 Honey consists of the monomers glucose and fructose
◦ A monosaccharide has a formula that is a
multiple of CH2O and contains hydroxyl groups
and a carbonyl group.

Example: Glucose has the formula

C6H12O6
◦ The monosaccharides glucose and fructose are
isomers
 That contain the same atoms but in
different arrangements
C
H
C
OH
C
O
C
H
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
Figure 3.4B
H
O
H
Glucose
HO
H
Fructose
◦ Monosaccharides can also occur as ring structures
6 CH2OH
H
5C
CH2OH
O
H
H
H
C 1
4C
OH
OH
3C
H
OH
O
H
OH
H
OH
HO
C2
H
H
H
O
OH
OH
Structural
formula
Figure 3.4C
Abbreviated
structure
Simplified
structure
3.5 Cells link two single sugars to form
disaccharides
◦ Monosaccharides can join to form disaccharides
 Such as sucrose (table sugar) and
maltose (brewing sugar)
CH2OH
CH2OH
O
O
H
HO
H
H
H
OH
H
H
OH
HO
OH
H
H
H
OH
Glucose
OH
H
OH
Glucose
H2O
CH2OH
H
HO
Figure 3.5
CH2OH
O
H
OH
H
H
OH
H
H
O
Maltose
O
H
OH
H
H
OH
H
OH
3.6 How sweet is sweet?
◦ Various types of molecules, including
nonsugars
Taste sweet because they bind to “sweet”
receptors on the tongue.
Table 3.6
3.7 Polysaccharides are long chains of sugar units
◦ Polysaccharides are polymers of monosaccharides
Linked together by dehydration reactions.
◦ Starch is a stored polysaccharide in plants. It
consists entirely of glucose monomers that form a
helix.
◦ Starch (potatoes) and glycogen (sugar stored in
animals) are polysaccharides that store sugar for
later use.
◦ Cellulose is a polysaccharide found in plant cell
walls and is the most abundance organic
compound on earth.
O
O
O
O
O
GLYCOGEN
O O
Cellulose fibrils in
a plant cell wall
O
O
O
O
O
O
O
O
O
O
CELLULOSE
OO
OO
O OH
OO
O OH
OO
O
OO
Figure 3.7
O
O O
O
Cellulose
molecules
O
O
O
Glycogen
granules in
muscle
tissue
Glucose
monomer
STARCH
Starch granules in
potato tuber cells
OO
OO
O O
O
O O
O

Unlike glycogen and starch, most animals
cannot break down by hydrolysis (insoluble
fiber).
◦ Cows and termites have cellulose-hydrolyzing
microorganisms that can digest cellulose.

Almost all carbohydrates are
◦ Hydrophilic (water loving), thus cotton bath towels
are quite absorbant.



Re- read 3.4 – 3.7 Carbohydrates
Fill in notes
Prepare for quiz 3.4 – 3.7
◦ Complete Chapter Objective 3.3 – 3.7
◦ On-line book support 3D & 3E
◦ Key Concept Quiz

Read 3.8 – 3.10
◦ Lipids are diverse compounds
 That consist mainly of carbon and
hydrogen atoms linked by nonpolar
covalent bonds.
◦ Lipids are grouped together

Figure 3.8A
Because they are hydrophobic (water fearing)
◦ Fats, also called triglycerides
 Are lipids whose main function is energy
storage.
 Consist of glycerol linked to three fatty acids
H
H
H C
C
OH OH
Figure 3.8B
H
H
C H
OH
Glycerol
HO
C O
H2O
CH2
CH2
CH2
CH2
CH2
Fatty acid
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
Figure 3.8C
H
H
H
C
C
C
O
O
O
C
O C
O C
H
O
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH3
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH3
◦ Phospholipids are a major component of cell
membranes.
◦ Waxes form waterproof coatings
◦ Steroids are often hormones
H3C
CH3
CH3
HO
Figure 3.9
CH3
CH3
3.10 Anabolic steroids pose health risks
◦ Anabolic steroids
Are synthetic variants of testosterone
Can cause serious health problems








Compromises your immune system
Can alter cholesterol levels
Depression and mood swings
Increase blood pressure
Infertility
Interfers with bone growth



Re- read 3.8 – 3.10 Lipids
Fill in notes
Prepare for quiz 3.8 – 3.10
◦ Complete Chapter Objective 3.8 – 3.10
◦ On-line book support 3F
◦ Key Concept Quiz

Read 3.11 – 3.16
◦ A protein




Is a polymer constructed from amino acid
monomers held together by peptide bonds.
They are thus referred to as: polypeptides.
There are 20 different amino acids
Proteins form different shapes, based upon the
order that the amino acids are strung together.
◦ Proteins
 Are involved in almost all of a cell’s
activities
◦ As enzymes
 They regulate chemical reactions.
Figure 3.11
3.12 Proteins are made from amino acids linked
by peptide bonds
◦ Protein diversity

Is based on different arrangements of a common
set of 20 amino acid monomers.
◦ Each amino acid contains
 An amino group
 A carboxyl group
 An R group, which distinguishes each of
the 20 different amino acids
H
O
H
N
C
H
C
OH
R
Amino
group
Figure 3.12A
Carboxyl (acid)
group
◦ Each amino acid has specific properties
Based on its structure

H
H
H
O
N
H
C
CH2
O
N
CH
CH3
H
C
OH
H
C
H
O
C
N
OH
H
OH
CH2
CH2
OH
C
Hydrophobic
Figure 3.12B
OH
Serine (Ser)
C
H
CH3
Leucine (Leu)
C
O
Aspartic acid (Asp)
Hydrophilic
◦ Cells link amino acids together
 By dehydration synthesis
◦ The bonds between amino acid monomers
 Are called peptide bonds
Carboxyl
group
Peptide
bond
Amino
group
H
H
H
O
N
H
C
C
H
+
OH
O
N
C
Dehydration
reaction
H
C
H
N
OH
R
R
Amino acid
Amino acid
H2O
H
H
O
C
C
R
H
N
C
H
R
Dipeptide
Figure 3.12C
O
C
OH
3.13 A protein’s specific shape determines its
function
◦ A protein consists of one or more polypeptide
chains
 Folded into a unique shape that
determines the protein’s function
Groove
Figure 3.13A
Groove
Figure 3.13B
3.14 A protein’s shape depends on four levels
of structure
Primary Structure
◦ A protein’s primary structure
 Is the sequence of amino acids forming
its polypeptide chains
Levels of Protein Structure
Leu Met
Pro
Primary structure
Gly
Thr
Gly Glu
Cys
Ser Lys
Asn Val
Val
Lys
Val
Ala
Leu Asp Ala Val Arg Gly Ser Pro
Amino acids
Figure 3.14A
Ala
Ile
Val
His Val
Phe
Arg
Secondary structure
◦ A protein’s secondary structure
 Is the coiling or folding of the chain,
stabilized by hydrogen bonding
Amino acids
Hydrogen
bond
C
C
N H
O C
Secondary structure
C
O C
N H
N H O C
C
C
C
H O
N H
O C
C
N
N H
O C
N H O C
R
C
H C
N H O
O C
C
C
N H
Alpha helix
Figure 3.14B
O H
H
O
N C CN
H
R CC N C CN
H
CC
O
H
O
O
H
O
C N CC
N
C
C H
H O C C N CN
H
O C
C
C
N
H
O
H
O
N C CN
H
CC N C C N
H
C
O
H
O
O
H
O
C N CC
N
H
C N C
H O C
CN
H
O C
Pleated sheet
Tertiary Structure
◦ A protein’s tertiary structure
 Is the overall three-dimensional shape of a
polypeptide
Tertiary structure
Polypeptide
(single subunit
of transthyretin)
Figure 3.14C
Quaternary Structure
◦ A protein’s quaternary structure
 Results from the association of two or
more polypeptide chains
Polypeptide
chain
Quaternary structure
Transthyretin, with
four identical
polypeptide subunits
Figure 3.14D
Collagen
3.19 Linus Pauling contributed to our
understanding of the chemistry of life
◦ Linus Pauling made important contributions
 To our understanding of protein
structure and function
Figure 3.15
3.20 Nucleic acids are information-rich
polymers of nucleotides
◦ Nucleic acids such as DNA and RNA
 Serve as the blueprints for proteins
and thus control the life of a cell
◦ The monomers of nucleic acids are nucleotides
 Composed of a sugar, phosphate, and
nitrogenous base
H
H
N
N
N
H
OH
O
P
N
O
CH2
Nitrogenous
base (A)
O

O
Phosphate
group
H
H
H
H
OH
Figure 3.16A
Sugar
N
H
H
◦ The sugar and phosphate form the backbone
for the nucleic acid or polynucleotide
A
T
C
G
T
Figure 3.16B
Sugar-phosphate
backbone
Nucleotide
◦ DNA consists of two polynucleotides
 Twisted around each other in a double helix
C
A
C
C
T
G
G
A
T
C
G
A
T
T
A
Base
pair
G
T
A
A
T
Figure 3.16C
A
C
T
◦ RNA, by contrast
 Is a single-stranded polynucleotide
◦ Stretches of a DNA molecules are called genes:
 Genes are the amino acid sequences
that code for proteins.