Chapter 3
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Transcript of Chapter 3
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Chapter 3Chapter 3
The Molecules of Life
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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 productsLaura Coronado Bio 10 Chapter 3
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Figure 3.00Laura Coronado Bio 10 Chapter 3
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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.
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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
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Animation: Carbon Skeletons
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Carbon skeletons vary in length Carbon skeletons may have double bonds,which can vary in location
Carbon skeletons may be unbranched or branched Carbon skeletons may be arranged in rings
Double bond
Figure 3.1Laura Coronado Bio 10 Chapter 3
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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.
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Structural formula Ball-and-stick model Space-filling model
Figure 3.2Laura Coronado Bio 10 Chapter 3
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Figure 3.3Laura Coronado Bio 10 Chapter 3
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Organic Molecule– Each type of organic molecule has a unique three-
dimensional 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)
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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
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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
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Animation: Polymers
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Short polymer Monomer
Dehydrationreaction
Longer polymer
a Building a polymer chain
Figure 3.4aLaura Coronado Bio 10 Chapter 3
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Hydrolysis Reaction
–Organisms also have to break down macromolecules.–Hydrolysis• Breaks bonds between monomers• Adds a molecule of water• Reverses the dehydration reaction
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Hydrolysis
b Breaking a polymer chain
Figure 3.4bLaura Coronado Bio 10 Chapter 3
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LARGE BIOLOGICAL MOLECULES
– There are four categories of large molecules in cells:• Carbohydrates• Lipids• Proteins• Nucleic acids
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Carbohydrates
–Carbohydrates are sugars or sugar polymers. They include• Small sugar molecules in soft drinks • Long starch molecules in pasta and potatoes
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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
form rings.Laura Coronado Bio 10 Chapter 3
Animation: L-Dopa
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Glucose Fructose
C6H12O6 C6H12O6
IsomersFigure 3.5
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Glucose Fructose
C6H12O6 C6H12O6
IsomersFigure 3.5a
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a Linear and ring structures
b Abbreviatedring structure
Figure 3.6Laura Coronado Bio 10 Chapter 3
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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
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Animation: Disaccharides
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Glucose Galactose
Lactose
Figure 3.7Laura Coronado Bio 10 Chapter 3
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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
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processed to extract
broken down into
converted to sweeter
added to foods ashigh-fructose corn syrup
Starch
Glucose
Fructose
Ingredients: carbonated water,high-fructose corn syrup,caramel color, phosphoric acid,natural flavors
Figure 3.8Laura Coronado Bio 10 Chapter 3
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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.
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Animation: Polysaccharides
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Glucosemonomer
a Starch
b Glycogen
c Cellulose
Starch granules
Glycogengranules
Cellulose fibril
Cellulosemolecules
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Glycogen
–Glycogen is• Used by animals cells to store energy• Converted to glucose when it is needed
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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
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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.
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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
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Oil (hydrophobic)
Vinegar (hydrophilic)
Figure 3.10Laura Coronado Bio 10 Chapter 3
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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”
Figure 3.11Laura Coronado Bio 10 Chapter 3
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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.
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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
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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
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Saturated Fats
TYPES OF FATS
Unsaturated Fats
Margarine
Plant oils Trans fats Omega-3 fats
INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED
COTTONSEED OIL, PARTIALLY HYDROGENATED
COTTONSEED OIL AND SOYBEAN OILS, MONO AND
DIGLYCERIDES, TBHO AND CITRIC ACID ANTIOXIDANTS
Figure 3.12Laura Coronado Bio 10 Chapter 3
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Figure 3.12b
Unsaturated Fats
Margarine
Plant oils Trans fats Omega-3 fats
INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED
COTTONSEED OIL, PARTIALLY HYDROGENATED
COTTONSEED OIL AND SOYBEAN OILS, MONO AND
DIGLYCERIDES, TBHO AND CITRIC ACID ANTIOXIDANTS
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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
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Cholesterol
Testosterone A type of estrogen
Figure 3.13Laura Coronado Bio 10 Chapter 3
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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
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THG
Figure 3.14Laura Coronado Bio 10 Chapter 3
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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
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MAJOR TYPES OF PROTEINS
Structural Proteins Storage Proteins Contractile Proteins Transport Proteins Enzymes
Figure 3.15Laura Coronado Bio 10 Chapter 3
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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.
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a The general structure of an amino acid
b Examples of amino acids with hydrophobic and hydrophilicside groups
Aminogroup
Carboxylgroup
Hydrophobicside group
Hydrophilicside group
Leucine Serine
Sidegroup
Figure 3.16Laura Coronado Bio 10 Chapter 3
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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.
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Aminogroup
Carboxylgroup
Sidegroup
Sidegroup
Amino acid Amino acid
Sidegroup
Sidegroup
Dehydration reaction
Peptide bond
Figure 3.17-2Laura Coronado Bio 10 Chapter 3
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Amino acid
1 510
20
15
253035
40
45
50 55
6065
70
75 8085
9095100
105
110 115
120125
129
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Normal red blood cell
Sickled red blood cell Sickle-cell hemoglobin
b Sickle-cell hemoglobin
a Normal hemoglobin
Normal hemoglobin
1 2 3 4 5 6 7. . . 146
1 2 3 4 5 6 7. . . 146
SEM
SEM
Figure 3.19Laura Coronado Bio 10 Chapter 3
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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
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a Primarystructure
b Secondary structure
Aminoacids
Pleated sheet
Alpha helix
c Tertiarystructure
Polypeptide
d Quaternarystructure
Protein withfour polypeptides
Figure 3.20-4Laura Coronado Bio 10 Chapter 3
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Protein
Target
Figure 3.21Laura Coronado Bio 10 Chapter 3
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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.
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Protein Structural Errors
–Misfolded proteins are associated with• Alzheimer’s disease•Mad cow disease• Parkinson’s disease
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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
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Gene
DNA
RNA
Protein
Amino acid
Nucleic acids
Figure 3.22Laura Coronado Bio 10 Chapter 3
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Nucleotides
– Nucleic acids are polymers of nucleotides.– Each nucleotide has three parts:
• A five-carbon sugar• A phosphate group• A nitrogenous base
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Figure 3.23
Nitrogenous baseA, G, C, or T
Thymine T
Phosphategroup
Sugardeoxyribose
a Atomic structure b Symbol used in this book
Phosphate
Base
Sugar
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DNA
– Each DNA nucleotide has one of the following bases:• Adenine (A)• Guanine (G)• Thymine (T)• Cytosine (C)
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Adenine A Guanine G
Thymine T Cytosine C
Adenine A Guanine G Thymine T Cytosine C
Space-filling model of DNAFigure 3.24
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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 sugar-phosphate backbone.
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Sugar-phosphatebackbone
NucleotideBasepair
Hydrogenbond
Bases
a DNA strandpolynucleotide
b Double helixtwo polynucleotide strands
Figure 3.25Laura Coronado Bio 10 Chapter 3
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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.
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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).
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Phosphategroup
Nitrogenous baseA, G, C, or U
Uracil U
Sugar ribose
Figure 3.26Laura Coronado Bio 10 Chapter 3
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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.
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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.
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DNA
Human cellDNA in 46
chromosomes
Chromosome 2one DNA molecule
Section ofchromosome 2
Lactase gene
14,000 nucleotides
C at this site causeslactose intoleranceT at this site causeslactose tolerance
Figure 3.27Laura Coronado Bio 10 Chapter 3
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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
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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.
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Large biologicalmolecules
Functions Components Examples
Carbohydrates
Lipids
Proteins
Nucleic acids
Dietary energy;storage; plantstructure
Long-termenergy storagefats;hormonessteroids
Enzymes, structure,storage, contraction,transport, and others
Informationstorage
Monosaccharides:glucose, fructoseDisaccharides:lactose, sucrosePolysaccharides:starch, cellulose
Fats triglycerides;Steroidstestosterone,estrogen
Lactasean enzyme,hemoglobina transport protein
DNA, RNA
Monosaccharide
Components ofa triglyceride
Amino acid
Nucleotide
Fatty acid
Glycerol
Aminogroup
Carboxylgroup
Sidegroup
PhosphateBase
Sugar
Figure UN3-2Laura Coronado Bio 10 Chapter 3
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Functions Components Examples
Dietary energy;storage; plantstructure
Monosaccharides:glucose, fructoseDisaccharides:lactose, sucrosePolysaccharides:starch, cellulose
Monosaccharide
Carbohydrates
Figure UN3-2aLaura Coronado Bio 10 Chapter 3
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Functions Components Examples
Lipids
Long-termenergy storagefats;hormonessteroids
Fats triglycerides;Steroidstestosterone,estrogenComponents of
a triglyceride
Fatty acid
Glycerol
Figure UN3-2bLaura Coronado Bio 10 Chapter 3
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Functions Components Examples
Proteins
Enzymes, structure,storage, contraction,transport, and others
Lactasean enzyme,hemoglobina transport protein
Amino acid
Aminogroup
Carboxylgroup
Sidegroup
Figure UN3-2cLaura Coronado Bio 10 Chapter 3
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Functions Components Examples
Nucleic acids
Informationstorage DNA, RNA
Nucleotide
PhosphateBase
Sugar
Figure UN3-2dLaura Coronado Bio 10 Chapter 3
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DNAdouble helix DNA strand DNA nucleotide
Base
Sugar
Phosphategroup
Figure UN3-4Laura Coronado Bio 10 Chapter 3