Chapter 3

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Chapter 3
The Molecules of Life
Laura Coronado
Bio 10
Chapter 3
Biology and Society: Got Lactose?
– Lactose is the main sugar found in milk.
– Some adults exhibit lactose intolerance, the inability to
properly digest lactose.
– Lactose-intolerant individuals are unable to digest
lactose properly.
• Lactose is broken down by bacteria in the large
intestine producing gas and discomfort.
– There is no treatment for the underlying cause of
lactose intolerance.
– Affected people must avoid lactose-containing foods or
take the enzyme lactase when eating dairy products
Laura Coronado
Bio 10
Chapter 3
Laura Coronado
Bio 10
Chapter 3
Figure 3.00
ORGANIC COMPOUNDS
– A cell is mostly water.
– The rest of the cell consists mainly of
carbon-based molecules.
– Carbon forms large, complex, and diverse
molecules necessary for life’s functions.
– Organic compounds are carbon-based
molecules.
Laura Coronado
Bio 10
Chapter 3
Carbon Chemistry
– Carbon is a versatile atom.
• It has four electrons in an outer shell that holds
eight.
• Carbon can share its electrons with other atoms to
form up to four covalent bonds.
– Carbon can use its bonds to
• Attach to other carbons
• Form an endless diversity of carbon skeletons
Animation: Carbon Skeletons
Laura Coronado
Bio 10
Chapter 3
Double bond
Carbon skeletons may have double bonds,
which can vary in location
Carbon skeletons vary in length
Carbon skeletons may be unbranched or branched
Laura Coronado
Carbon skeletons may be arranged in rings
Bio 10
Chapter 3
Figure 3.1
Hydrocarbons
– The simplest organic compounds are
hydrocarbons, which are organic molecules
containing only carbon and hydrogen
atoms.
– The simplest hydrocarbon is methane,
consisting of a single carbon atom bonded
to four hydrogen atoms.
Laura Coronado
Bio 10
Chapter 3
Structural formula
Ball-and-stick model
Laura Coronado
Bio 10
Space-filling model
Chapter 3
Figure 3.2
Laura Coronado
Bio 10
Chapter 3
Figure 3.3
Organic Molecule
– Each type of organic molecule has a unique threedimensional shape.
– The shapes of organic molecules relate to their
functions.
– The unique properties of an organic compound depend
on
• Its carbon skeleton
• The atoms attached to the skeleton
– The groups of atoms that usually participate in chemical
reactions are called functional groups. Two common
examples are
• Hydroxyl groups (-OH)
• Carboxyl groups (C=O)
Laura Coronado
Bio 10
Chapter 3
Giant Molecules from Smaller
Building Blocks
– On a molecular scale, many of life’s
molecules are gigantic, earning the name
macromolecules.
– Three categories of macromolecules are
• Carbohydrates
• Proteins
• Nucleic acids
Laura Coronado
Bio 10
Chapter 3
Giant Molecules from Smaller
Building Blocks
– Most macromolecules are polymers.
– Polymers are made by stringing together
many smaller molecules called monomers.
– A dehydration reaction
• Links two monomers together
• Removes a molecule of water
Animation: Polymers
Laura Coronado
Bio 10
Chapter 3
Short polymer
Monomer
Dehydration
reaction
Longer polymer
a Building a polymer chain
Laura Coronado
Bio 10
Chapter 3
Figure 3.4a
Hydrolysis Reaction
– Organisms also have to break down
macromolecules.
– Hydrolysis
• Breaks bonds between monomers
• Adds a molecule of water
• Reverses the dehydration reaction
Laura Coronado
Bio 10
Chapter 3
Hydrolysis
b Breaking a polymer chain
Laura Coronado
Bio 10
Chapter 3
Figure 3.4b
LARGE BIOLOGICAL MOLECULES
– There are four categories of large molecules
in cells:
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
Laura Coronado
Bio 10
Chapter 3
Carbohydrates
– Carbohydrates are sugars or sugar
polymers. They include
• Small sugar molecules in soft drinks
• Long starch molecules in pasta and potatoes
Laura Coronado
Bio 10
Chapter 3
Monosaccharides
– Monosaccharides are simple sugars that cannot
be broken down by hydrolysis into smaller
sugars.
– Glucose and fructose are isomers, molecules
that have the same molecular formula but
different structures.
– Monosaccharides are the main fuels for cellular
work.
– In aqueous solutions, many monosaccharides
Animation: L-Dopa
form rings.
Laura Coronado
Bio 10
Chapter 3
Glucose
Fructose
C6H12O6
Laura Coronado
Bio 10
C6H12O6
Isomers
Figure 3.5
Chapter 3
Glucose
Fructose
C6H12O6
C6H12O6
Isomers
Laura Coronado
Bio 10
Chapter 3
Figure 3.5a
b Abbreviated
ring structure
a Linear and ring structures
Laura Coronado
Bio 10
Chapter 3
Figure 3.6
Disaccharides
– A disaccharide is
• A double sugar
• Constructed from two monosaccharides
• Formed by a dehydration reaction
– Disaccharides include
• Lactose in milk
• Maltose in beer, malted milk shakes, and malted
milk ball candy
• Sucrose in table sugar
Animation: Disaccharides
Laura Coronado
Bio 10
Chapter 3
Galactose
Glucose
Lactose
Laura Coronado
Bio 10
Chapter 3
Figure 3.7
Disaccharides
– Sucrose is
• The main carbohydrate in plant sap
• Rarely used as a sweetener in processed foods
– High-fructose corn syrup is made by a
commercial process that converts natural
glucose in corn syrup to much sweeter fructose.
– The United States is one of the world’s leading
markets for sweeteners.
• The average American consumes about 45 kg of
sugar (about 100 lbs.) per year.
Laura Coronado
Bio 10
Chapter 3
processed to extract
Starch
broken down into
Glucose
converted to sweeter
Fructose
added to foods as
high-fructose corn syrup
Ingredients: carbonated water,
high-fructose corn syrup,
caramel color, phosphoric acid,
natural flavors
Laura Coronado
Bio 10
Chapter 3
Figure 3.8
Polysaccharides
– Polysaccharides are
• Complex carbohydrates
• Made of long chains of sugar units and polymers
of monosaccharides
– Starch is an example of a polysaccharide
• Used by plant cells to store energy
• Potatoes and grains are major sources of starch in
the human diet.
Animation: Polysaccharides
Laura Coronado
Bio 10
Chapter 3
Glucose
monomer
Starch granules
a Starch
Glycogen
granules
b Glycogen
Cellulose fibril
Cellulose
molecules
c Cellulose
Laura Coronado
Bio 10
Chapter 3
Figure 3.9
Glycogen
– Glycogen is
• Used by animals cells to store energy
• Converted to glucose when it is needed
Laura Coronado
Bio 10
Chapter 3
Cellulose
– Cellulose
• Is the most abundant organic compound on Earth
• Forms cable-like fibrils in the tough walls that
enclose plants
• Cannot be broken apart by most animals
Laura Coronado
Bio 10
Chapter 3
Carbohydrates in Water
– Monosaccharides and disaccharides dissolve
readily in water.
– Cellulose does not dissolve readily in water.
– Almost all carbohydrates are hydrophilic, or
“water-loving,” adhering water to their
surface.
Laura Coronado
Bio 10
Chapter 3
Lipids & Fats
– Lipids are
• Neither macromolecules nor polymers
• Hydrophobic, unable to mix with water
• A typical fat, or triglyceride, consists of a glycerol
molecule joined with three fatty acid molecules via
a dehydration reaction.
• Essential functions in the human body including
• Energy storage
• Cushioning
• Insulation
Laura Coronado
Bio 10
Chapter 3
Oil (hydrophobic)
Vinegar (hydrophilic)
Laura Coronado
Bio 10
Chapter 3
Figure 3.10
Fatty acid
Glycerol
(a) A dehydration reaction linking a fatty acid to glycerol
(b) A fat molecule with a glycerol “head” and three
energy-rich hydrocarbon fatty acid “tails”
Laura Coronado
Bio 10
Chapter 3
Figure 3.11
Fatty Acid
– If the carbon skeleton of a fatty acid has
• Fewer than the maximum number of hydrogens, it
is unsaturated
• The maximum number of hydrogens, then it is
saturated
– A saturated fat has no double bonds, and all
three of its fatty acids are saturated.
Laura Coronado
Bio 10
Chapter 3
Lipids & Fats
– Most plant oils tend to be low in saturated
fatty acids and liquid at room temperature.
– Most animal fats
• Have a high proportion of saturated fatty acids
• Can easily stack, tending to be solid at room
temperature
• Contribute to atherosclerosis, a condition in
which lipid-containing plaques build up within
the walls of blood vessels
Laura Coronado
Bio 10
Chapter 3
Hydrogenation
– Hydrogenation
• Adds hydrogen
• Converts unsaturated fats to saturated fats
• Makes liquid fats solid at room temperature
• Creates trans fat, a type of unsaturated fat that is
even less healthy than saturated fats
Laura Coronado
Bio 10
Chapter 3
TYPES OF FATS
Saturated Fats
Unsaturated Fats
Margarine
INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED
COTTONSEED OIL, PARTIALLY HYDROGENATED
COTTONSEED OIL AND SOYBEAN OILS, MONO AND
DIGLYCERIDES, TBHO AND CITRIC ACID
Trans fats
Plant oils
Laura Coronado
ANTIOXIDANTS
Bio 10
Chapter 3
Figure 3.12
Omega-3 fats
Unsaturated Fats
Margarine
INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED
COTTONSEED OIL, PARTIALLY HYDROGENATED
COTTONSEED OIL AND SOYBEAN OILS, MONO AND
DIGLYCERIDES, TBHO AND CITRIC ACID ANTIOXIDANTS
Plant oils
Trans fats
Laura Coronado
Bio 10
Omega-3 fats
Chapter 3
Figure 3.12b
Steroids
– Steroids are very different from fats in
structure and function.
• The carbon skeleton is bent to form four fused
rings.
• Steroids vary in the functional groups attached to
this core set of rings.
– Cholesterol
• A key component of cell membranes
• The “base steroid” from which your body produces
other steroids, such as estrogen and testosterone
Laura Coronado
Bio 10
Chapter 3
Cholesterol
Testosterone
A type of estrogen
Laura Coronado
Bio 10
Chapter 3
Figure 3.13
Steroids
– Synthetic anabolic steroids
• Resemble testosterone
• Mimic some of its effects
• Can cause serious physical and mental problems
• Are abused by athletes to enhance performance
Laura Coronado
Bio 10
Chapter 3
THG
Laura Coronado
Bio 10
Chapter 3
Figure 3.14
Proteins
– Proteins
• Are polymers constructed from amino acid
monomers
• Perform most of the tasks the body needs to
function
• Form enzymes, chemicals that change the rate of a
chemical reaction without being changed in the
process
Laura Coronado
Bio 10
Chapter 3
MAJOR TYPES OF PROTEINS
Structural Proteins
Storage Proteins
Contractile Proteins
Laura Coronado
Bio 10
Transport Proteins
Chapter 3
Figure 3.15
Enzymes
The Monomers of Proteins: Amino
Acids
– All proteins are constructed from a common
set of 20 kinds of amino acids.
– Each amino acid consists of a central carbon
atom bonded to four covalent partners in
which three of those attachment groups are
common to all amino acids.
Laura Coronado
Bio 10
Chapter 3
Amino
group
Carboxyl
group
Side
group
a The general structure of an amino acid
Hydrophobic
side group
Hydrophilic
side group
Leucine
Serine
b Examples of amino acids with hydrophobic and hydrophilic
side groups
Laura Coronado
Bio 10
Chapter 3
Figure 3.16
Proteins as Polymers
– Cells link amino acids together by dehydration
reactions, forming peptide bonds and creating
long chains of amino acids called
polypeptides.
– Your body has tens of thousands of different
kinds of protein.
– Proteins differ in their arrangement of amino
acids.
– The specific sequence of amino acids in a
protein is its primary structure.
Laura Coronado
Bio 10
Chapter 3
Carboxyl
group
Amino
group
Side
group
Side
group
Amino acid
Amino acid
Dehydration reaction
Side
group
Side
group
Peptide bond
Laura Coronado
Bio 10
Chapter 3
Figure 3.17-2
15
5
1
10
30
35
20
25
45
40
50
55
65
60
70
75
Amino acid
85
80
95
100
90
110
115
105
125
120
129
Laura Coronado
Bio 10
Chapter 3
Figure 3.18
SEM
1
2
Normal red blood cell
3
4
5
6
7. . . 146
Normal hemoglobin
SEM
a Normal hemoglobin
1
Sickled red blood cell
b Sickle-cell hemoglobin Laura Coronado
2
3
4
5
6
Sickle-cell hemoglobin
Bio 10
Chapter 3
Figure 3.19
7. . . 146
Protein Shape
– A functional protein consists of one or more
polypeptide chains, precisely folded and coiled
into a molecule of unique shape.
– Proteins consisting of
• One polypeptide have three levels of structure
• More than one polypeptide chain have a fourth,
quaternary structure
– A protein’s three-dimensional shape
• Recognizes and binds to another molecule
• Enables the protein to carry out its specific function
in a cell
Laura Coronado
Bio 10
Chapter 3
Amino
acids
b Secondary structure
c Tertiary
structure
d Quaternary
structure
a Primary
structure
Pleated sheet
Protein with
four polypeptides
Polypeptide
Alpha helix
Laura Coronado
Bio 10
Chapter 3
Figure 3.20-4
Target
Protein
Laura Coronado
Bio 10
Chapter 3
Figure 3.21
What Destroys Protein Shape?
– A protein’s shape is sensitive to the
surrounding environment.
– Unfavorable temperature and pH changes
can cause denaturation of a protein, in
which it unravels and loses its shape.
– High fevers (above 104º F) in humans can
cause some proteins to denature.
Laura Coronado
Bio 10
Chapter 3
Protein Structural Errors
– Misfolded proteins are associated with
• Alzheimer’s disease
• Mad cow disease
• Parkinson’s disease
Laura Coronado
Bio 10
Chapter 3
Genetic Information
– Nucleic acids are macromolecules that provide the
directions for building proteins
• Include DNA and RNA
• Are the genetic material that organisms inherit
from their parents
– DNA resides in cells in long fibers called
chromosomes.
– A gene is a specific stretch of DNA that programs
the amino acid sequence of a polypeptide.
– The chemical code of DNA must be translated from
“nucleic acid language” to “protein language.”
Laura Coronado
Bio 10
Chapter 3
Gene
DNA
Nucleic acids
RNA
Amino acid
Protein
Laura Coronado
Bio 10
Chapter 3
Figure 3.22
Nucleotides
– Nucleic acids are polymers of nucleotides.
– Each nucleotide has three parts:
•
•
•
A five-carbon sugar
A phosphate group
A nitrogenous base
Laura Coronado
Bio 10
Chapter 3
Nitrogenous base
A, G, C, or T
Thymine T
Phosphate
group
Phosphate
Base
Sugar
deoxyribose
Sugar
a Atomic structure
b Symbol used in this book
Laura Coronado
Bio 10
Chapter 3
Figure 3.23
DNA
– Each DNA nucleotide has one of the following
bases:
• Adenine (A)
• Guanine (G)
• Thymine (T)
• Cytosine (C)
Laura Coronado
Bio 10
Chapter 3
Adenine A
Guanine G
Thymine T
Adenine A
Cytosine C
Guanine G
Space-filling model of DNA
Laura Coronado
Thymine T
Bio 10
Cytosine C
Chapter 3
Figure 3.24
DNA Linkages
– Dehydration reactions
• Link nucleotide monomers into long chains called
polynucleotides
• Form covalent bonds between the sugar of one
nucleotide and the phosphate of the next
• Form a sugar-phosphate backbone
– Nitrogenous bases hang off the sugarphosphate backbone.
Laura Coronado
Bio 10
Chapter 3
Sugar-phosphate
backbone
Nucleotide
Base
pair
Hydrogen
bond
Bases
a DNA strand
polynucleotide
Laura Coronado
b Double helix
two
polynucleotide
strands
Bio 10
Chapter 3
Figure 3.25
DNA Linkages
– Two strands of DNA join together to form a
double helix.
– Bases along one DNA strand hydrogen-bond to
bases along the other strand.
– The functional groups hanging off the base
determine which bases pair up:
• A only pairs with T.
• G can only pair with C.
Laura Coronado
Bio 10
Chapter 3
RNA
– RNA, ribonucleic acid, is different from DNA.
• RNA is usually single-stranded but DNA usually
exists as a double helix.
• RNA uses the sugar ribose and the base uracil (U)
instead of thymine (T).
Laura Coronado
Bio 10
Chapter 3
Nitrogenous base
A, G, C, or U
Uracil U
Phosphate
group
Sugar ribose
Laura Coronado
Bio 10
Chapter 3
Figure 3.26
The Process of Science:
Does Lactose Intolerance Have a
Genetic Basis?
– Observation: Most lactose-intolerant people
have a normal version of the lactase gene.
– Question: Is there a genetic basis for lactose
intolerance?
– Hypothesis: Lactose-intolerant people have a
mutation but not within the lactase gene.
Laura Coronado
Bio 10
Chapter 3
The Process of Science:
Does Lactose Intolerance Have a
Genetic Basis?
– Prediction: A mutation would be found nearby
the lactase gene.
– Experiment: Genes of 196 lactose-intolerant
people were examined.
– Results: A 100% correlation between lactose
intolerance and one mutation was found.
Laura Coronado
Bio 10
Chapter 3
DNA
Lactase gene
14,000 nucleotides
Human cell
DNA in 46
chromosomes
Chromosome 2
one DNA molecule
Laura Coronado
Bio 10
Section of
chromosome 2
Chapter 3
C at this site causes
lactose intolerance
T at this site causes
lactose tolerance
Figure 3.27
Evolution Connection:
Evolution and Lactose Intolerance in Humans
– Most people are lactose-intolerant as adults:
• African Americans and Native Americans — 80%
• Asian Americans — 90%
• But only 10% of Americans of northern European
descent are lactose-intolerant
Laura Coronado
Bio 10
Chapter 3
Lactose Tolerance
– Lactose tolerance appears to have evolved in
northern European cultures that relied upon
dairy products.
– Ethnic groups in East Africa that rely upon
dairy products are also lactose tolerant but
due to different mutations.
Laura Coronado
Bio 10
Chapter 3
Large biological
molecules
Carbohydrates
Functions
Components
Examples
Monosaccharides:
glucose, fructose
Disaccharides:
lactose, sucrose
Polysaccharides:
starch, cellulose
Dietary energy;
storage; plant
structure
Monosaccharide
Lipids
Long-term
energy storage
fats;
hormones
steroids
Fatty acid
Glycerol
Components of
a triglyceride
Amino
group
Proteins
Enzymes, structure,
storage, contraction,
transport, and others
Fats triglycerides;
Steroids
testosterone,
estrogen
Carboxyl
group
Side
group
Lactase
an enzyme,
hemoglobin
a transport protein
Amino acid
Phosphate
Base
Nucleic acids
Information
storage
DNA, RNA
Sugar
Laura Coronado
Nucleotide
Bio 10
Chapter 3
Figure UN3-2
Carbohydrates
Functions
Components
Examples
Monosaccharides:
glucose, fructose
Disaccharides:
lactose, sucrose
Polysaccharides:
starch, cellulose
Dietary energy;
storage; plant
structure
Monosaccharide
Laura Coronado
Bio 10
Chapter 3
Figure UN3-2a
Lipids
Functions
Long-term
energy storage
fats;
hormones
steroids
Components
Examples
Fatty acid
Glycerol
Components of
a triglyceride
Laura Coronado
Bio 10
Chapter 3
Fats triglycerides;
Steroids
testosterone,
estrogen
Figure UN3-2b
Proteins
Functions
Components
Examples
Amino
group
Enzymes, structure,
storage, contraction,
transport, and others
Carboxyl
group
Lactase
an enzyme,
hemoglobin
a transport protein
Side
group
Amino acid
Laura Coronado
Bio 10
Chapter 3
Figure UN3-2c
Nucleic acids
Functions
Components
Examples
Phosphate
Base
Information
storage
DNA, RNA
Sugar
Nucleotide
Laura Coronado
Bio 10
Chapter 3
Figure UN3-2d
Base
Phosphate
group
Sugar
DNA
double helix
DNA strand
Laura Coronado
DNA nucleotide
Bio 10
Chapter 3
Figure UN3-4
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