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Copyright © 2009 Pearson Education, Inc..
Including the lecture Materials of
Gregory AhearnUniversity of North Florida
with amendments andadditions by
John Crocker
Chapter 2pt 3
Atoms, Molecules, and Life
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2.5 How Are Biological Molecules Joined Together Or Broken Apart? Biomolecules are polymers (chains) of
subunits called monomers A huge number of different polymers can be
made from a small number of monomers Biomolecules Are Joined Through
Dehydration and Broken by Hydrolysis
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Organic Molecule Synthesis
Monomers are joined together through dehydration synthesis An H and an OH are removed, resulting in the
loss of a water molecule (H2O)
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Organic Molecule Synthesis
Polymers are broken apart through hydrolysis (“water cutting”) Water is broken into H and OH and used to
break the bond between monomers
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Organic Molecule Synthesis
All biological molecules fall into one of four categoriesCarbohydratesLipidsProteinsNucleic Acids
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2.6 What Are Carbohydrates?
Composition:C, H, and O in the ratio of 1:2:1
Construction: Simple or single sugars are
monosaccharides Two linked monosaccharides are
disaccharides Long chains of monosaccharides are
polysaccharides
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Monosaccharides
Basic monosaccharide structure Backbone of 3-7 carbon atoms Many –OH and –H functional groups Usually found in a ring form in cells
Simple sugars provide important energy sources for organisms.
Most small carbs are water-soluble due to the polar OH functional groups
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A simple sugar
Fig. 2-13
Glucose, linear form Glucose, ring form(a) (b)H
H
CH2OH
HO
OH
OH
O
H H
OH H
2356 4 1
H H H H
H
H
H
H
H H
H
H
O OOOO
O
CCCCCC
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Monosaccharides
Example monosaccharides continued Fructose (found in corn syrup and fruits) Galactose (found in lactose) Ribose and deoxyribose (found in RNA and
DNA)
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Most small carbs are water-soluble due to the polar OH functional groups
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Disaccharides
Disaccharides are two-part sugars Sucrose (table sugar) = glucose + fructose Lactose (milk sugar) = glucose + galactose Maltose (malt sugar)= glucose + glucose
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Manufacture of a disaccharide
Fig. 2-14
glucose fructose sucrose
dehydrationsynthesis
OHO
OHOCH2
OH
HO
CH2OH
H H
OH
H OH
H
H
O HO
OCH2OH
H H
OH
H OH
H
HH
H
H
HOCH2OHH
HOCH2 H
H
H
HOCH2OH
O
OH
O
+
OHH
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Polysaccharides
Monosaccharides are linked together to form chains (polysaccharides)
Polysaccharides are used for energy storage and structural components
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Polysaccharides
Storage polysaccharides Starch (polymer of glucose)
Formed in roots and seeds as a form of glucose storage
Glycogen (polymer of glucose)Found in liver and muscles
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Polysaccharides
Structural polysaccharides Cellulose (polymer of glucose) Found in the cell walls of plants
Indigestible for most animals due to orientation of bonds between glucoses
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Polysaccharides
Structural polysaccharides continued Chitin (polymer of modified glucose units)
Found in the outer coverings of insects, crabs, and spiders
Found in the cell walls of many fungi
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2.7 What Are Lipids?
Molecular characteristics of lipids Lipids are molecules with long regions
composed almost entirely of carbon and hydrogen.
The nonpolar regions of carbon and hydrogen bonds make lipids hydrophobic and insoluble in water.
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What Are Lipids?
Lipids are diverse in structure and serve in a variety of functions Energy storage Waterproofing Membranes in cells Hormones
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Lipid classification Group 1: Oils, fats, and waxes Group 2: Phospholipids Group 3: Steroids
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Group 1: Oils, fats, and waxes Formed by dehydration synthesis
3 fatty acids + glycerol triglyceride Contain only carbon, hydrogen, and oxygen Contain one or more fatty acid subunits in
long chains of C and H with a carboxyl group(–COOH)
Ring structure is rare
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Group 1: Oils, fats, and waxes (continued) Fats and oils form by dehydration synthesis
from three fatty acid subunits and one molecule of glycerol.
Fig. 2-16
glycerol fatty acids
CH2CHO CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.O
CH2CHO CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.O
CH2CHO CH2 CH2 CH2 CH2 CH2 CH2 CHO
C OHHH
C OHH
C OHHH
CH2CH
CH2
CH2
etc.
+
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triglyceride 3 watermolecules
OHH
OHH
OHH
+
+
CH2C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.O
CH2C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2
CH2
CH2 etc.O
CH2C CH2 CH2 CH2 CH2 CH2 CH2 CHO
CHH
CH
C
O
O
OHH
CH2CH
CH2
CH2
etc.
+
Group 1: Oils, fats, and waxes (continued) Fats and oils formed by dehydration synthesis
are called triglycerides. Triglycerides are used for long-term energy
storage in both plants and animals.
Fig. 2-16
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Group 1: Oils, fats, and waxes (continued) Characteristics of fats
Solidity is due to the prevalence of single or double carbon bonds
Fats are solid at room temperature. Fats have all carbons joined by single covalent
bonds. The remaining bond positions on the carbons are
occupied by hydrogen atoms.
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Beef fat (saturated)(a)
Group 1: Oils, fats, and waxes (continued) Fatty acids of fats are said to be saturated and
are straight molecules that can be stacked.
Fig. 2-18a
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Group 1: Oils, fats, and waxes (continued) Characteristics of oils
Oils are liquid at room temperature.Some of the carbons in fatty acids have
double covalent bonds.There are fewer attached hydrogen atoms,
and the fatty acid is said to be unsaturated.
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Group 1: Oils, fats, and waxes (continued) Unsaturated fatty acids have bends and kinks
in fatty acid chains and can’t be stacked.
Fig. 2-18b
Peanut oil (unsaturated)(b)
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Group 1: Oils, fats, and waxes (continued) Characteristics of waxes
Waxes are solid at room temperature.Waxes are highly saturated.Waxes are not a food source.Waxes are composed of long hydrocarbon
chains and are strongly hydrophobic
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Group 1: Oils, fats, and waxes (continued) Waxes form waterproof coatings
Leaves and stems of plantsFur in mammals Insect exoskeletons
Used to build honeycomb structures
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Group 1: Oils, fats, and waxes (continued) Bees use waxes to store food and honey.
Fig. 2-17b
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Group 2: PhospholipidsPhospholipids: form dual layered plasma
membranes around all cells Construction
like oils except one fatty acid is replaced by a phosphate group attached to glycerol.
2 fatty acids + glycerol + a short polar functional group
water-soluble heads and water-insoluble tails.
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polar head glycerol
(hydrophilic) (hydrophobic)
fatty acid tails
CH3 O–
OO
CH3
CH CH2CH2
CH2CH2
CH2CH2
CH2CH3
H3C N+- CH2 - CH2 -O-P-O-CH2 O
HC-O-C-CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH
H2C-O-C- CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH3
-
Group 2: Phospholipids (continued) The phosphate end of the molecule is water
soluble; the fatty acid end of the molecule is water insoluble.
Fig. 2-19
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Group 3: Steroids Steroids contain four fused carbon rings. Various functional groups protrude from the
basic steroid “skeleton”. Examples of steroids
CholesterolFound in membranes of animal cells
Male and female sex hormones
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2.8 What Are Proteins? Functions of proteins
Proteins act as enzymes to catalyze (speed) many biochemical reactions.
They provide structure (ex/ elastin) They can act as energy stores. They are involved in carrying oxygen around
the body (hemoglobin). They are involved in muscle movement.
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Some proteins are structural and provide support in hair, horns, spider webs, etc.
Fig. 2-21
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Proteins are formed from chains of amino acids.
All amino acids have the same basic structure: A central carbon An attached amino group An attached carboxyl group An attached variable group (R group)
Some are hydrophobicSome are hydrophilic
aminogroup
hydrogen
variablegroup
carboxylicacid group
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Amino acid monomers join to form chains by dehydration synthesis. Proteins are formed by dehydration reactions
between individual amino acids. The –NH2 group of one amino acid is joined to
the –COOH group of another, with the release of H2O and the formation of a new peptide (two or more amino acids).
The resultant covalent bond is a peptide bond
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Long chains of amino acids are known as polypeptides or just proteins
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The sequence of amino acids in a protein dictates its three dimensional structure
This structure gives proteins their functions. Long chains of amino acids fold into three-
dimensional shapes in cells, which allows the protein to perform its specific functions.
When a protein is denatured, its shape has been disrupted and it may not be able to perform its function.
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Four Levels of Structure
Proteins exhibit up to four levels of structure Primary structure is the sequence of amino
acids linked together in a protein Secondary structures are helices and
pleated sheets Tertiary structure refers to complex foldings
of the protein chain held together by disulfide bridges, hydrophobic/hydrophilic interactions, and other bonds
Quaternary structure is found where multiple protein chains are linked together
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Three Dimensional Structures
The type, position, and number of amino acids determine the structure and function of a protein Precise positioning of amino acid R groups
leads to bonds that determine secondary and tertiary structure
Disruption of these bonds leads to denatured proteins and loss of function
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2.9 What Are Nucleic Acids?
Structure of nucleic acids Nucleic acids are long chains of similar, but
not identical, subunits called nucleotides.
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2.9 What Are Nucleic Acids?
Structure of nucleic acids (continued) All nucleotides have three parts.
A five-carbon sugar (ribose or deoxyribose)A phosphate groupA nitrogen-containing molecule called a
base
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phosphate
base
sugar
P O
O
OCH2
H
OH
H HH
H
OH
HO
C
N CH
NC
C
NHC
N
NH2
2.9 What Are Nucleic Acids?
Deoxyribose nucleotide
Fig. 2-25
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2.9 What Are Nucleic Acids?
Types of nucleotides Those that contain the sugar ribose. Those that contain the sugar deoxyribose. Nucleotides string together in long chains as
nucleic acids with the phosphate group of one nucleotide bonded to the sugar group of another.
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phosphate
base
sugar
2.9 What Are Nucleic Acids?
Nucleotide chain
Fig. 2-26
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2.9 What Are Nucleic Acids?
DNA and RNA, the molecules of heredity, are nucleic acids. There are two types of nucleic acids.
Deoxyribonucleic acid (DNA): contains the genetic code of cell
Ribonucleic acid (RNA): is used in the synthesis of proteins
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2.9 What Are Nucleic Acids?
Other nucleotides perform other functions. Adenosine monophosphate: acts as a
messenger in the cell, carrying information to other molecules
Adenosine triphosphate: carries energy from place to place in the cell
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Section 3.6 Outline
What Are Nucleic Acids? Structure of Nucleic Acids DNA and RNA, the Molecules of Heredity, Are
Nucleic Acids Other Nucleotides Act as Intracellular
Messengers, Energy Carriers, or Coenzymes
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What Are Nucleic Acids?
Nucleotides are the monomers of nucleic acid chains
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What Are Nucleic Acids?
All nucleotides are made of three parts Phosphate group Five-carbon sugar Nitrogen-containing base
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Molecules of Heredity
Two types of nucleotides Ribonucleotides (A, G, C, and U) found in
RNA Deoxyribonucleotides (A, G, C, and T) found
in DNA
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Molecules of Heredity
Two types of polymers of nucleic acids DNA (deoxyribonucleic acid) found in
chromosomes Carries genetic information needed for
protein construction RNA (ribonucleic acid)
Copies of DNA used directly in protein construction
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Molecules of Heredity
Each DNA molecule consists of two chains of nucleotides that form a double helix
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Other Nucleotides
Nucleotides as intracellular messengers Cyclic nucleotides (e.g. cyclic AMP) carry
chemical signals between molecule
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Other Nucleotides
Nucleotides as energy carriers Adenosine triphosphate (ATP) carries
energy stored in bonds between phosphate groups
NAD+ and FAD carry electrons
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Other Nucleotides
Nucleotides as enzyme assistants Coenzymes help enzymes promote and guide
chemical reactions
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