Transcript 2.9 What Are Nucleic Acids?

Chapter 2
pt 3
Atoms, Molecules,
and Life
Including the lecture
Materials of
Gregory Ahearn
University of North Florida
with amendments and
additions by
John Crocker
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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
categories
Carbohydrates
Lipids
Proteins
Nucleic 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
CH2OH
H
O
H
6
H
H
5
C
H
4
C
O
O
H
3
C
2
C
O
H
H
O
H
H
(a) Glucose, linear form
H
1
C
C
O
O
H
H
H
H
HO
OH
H
H
OH
OH
(b) Glucose, ring form
Fig. 2-13
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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
glucose
fructose
CH2OH
O
H H
HOCH2
CH2OH
O
O
H
H
+
HO
OH
H
H
OH
OH
sucrose
HO
H
OH
HO
H
dehydration
CH2OH synthesis
H H
HO
HOCH2
H
OH
H
H
OH
O
H
OH
O
H
HO
CH2OH
H
O
H
H
Fig. 2-14
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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.
etc.
CH2
CH2
CH2
H
H C OH
O
CH
HO C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH
H C OH
O
HO C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.
+
H C OH
H
glycerol
O
HO C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.
fatty acids
Fig. 2-16
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 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.
etc.
CH2
CH2
CH2
H
O
CH
H C O C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH
+
O
H
O
O
H C O C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.
+
H
O
H C O C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.
H
+
H
triglyceride
H
H
O
H
3 water
molecules
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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 Group 1: Oils, fats, and waxes (continued)
 Fatty acids of fats are said to be saturated and
are straight molecules that can be stacked.
(a) Beef fat (saturated)
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.
(b) Peanut oil (unsaturated)
Fig. 2-18b
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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 plants
 Fur 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: Phospholipids
Phospholipids: 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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 Group 2: Phospholipids (continued)
 The phosphate end of the molecule is water
soluble; the fatty acid end of the molecule is
water insoluble.
CH3
O–
H3C - N+- CH2 - CH2 -O-P- O -CH2 O
CH3
O HC-O-C- CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH
O
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
H2C-O-C- CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH3
polar head
glycerol
(hydrophilic)
fatty acid tails
(hydrophobic)
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
 Cholesterol
 Found 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)
variable
 Some are hydrophobic
group
 Some are hydrophilic
amino
group
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carboxylic
acid group
hydrogen
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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 threedimensional 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 group
 A nitrogen-containing molecule called a
base
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2.9 What Are Nucleic Acids?
Deoxyribose nucleotide
base
NH2
phosphate
N C C
N
OH
HO
P
HC
O
CH2
O
H
N C N CH
O
sugar
H
H
OH
H
H
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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2.9 What Are Nucleic Acids?
Nucleotide chain
base
sugar
phosphate
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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