Chapter 23
Preview
•
•
•
•
Lesson Starter
Objectives
Carbohydrates
Lipids
Chapter 23
Section 1 Carbohydrates and Lipids
Lesson Starter
• Why does the can of diet soft drink float and the can
of regular soft drink sink?
• The aspartame used to sweeten the diet soft drink is
about 200 times as sweet as sucrose.
• The regular soft drink is denser than the diet soft
drink, because there is such a large amount of sugar
in the regular soft drink, and only a small amount of
sweetener in the diet soft drink.
Chapter 23
Section 1 Carbohydrates and Lipids
Objectives
• Describe the structural characteristics of simple
carbohydrates and complex carbohydrates.
• Explain the role of carbohydrates in living systems.
• Describe the structural characteristics of lipid
molecules.
• Identify the functions of lipids in living cells.
Chapter 23
Section 1 Carbohydrates and Lipids
• Biochemistry is the study of the chemicals and
reactions that occur in living things.
• Biochemical compounds are often large and complex
organic molecules, but their chemistry is similar to
that of the smaller organic molecules
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates
• Carbohydrates are molecules that are composed of
carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio,
and provide nutrients to the cells of living things.
• sugars, starches, and cellulose
• Carbohydrates are produced by plants through a
process called photosynthesis.
• Carbohydrates provide nearly all of the energy that is
available in most plant-derived food.
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates
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Visual Concept
Chapter 23
Section 1 Carbohydrates and Lipids
Types of Carbohydrates
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates, continued
Monosaccharides
• A monosaccharide is a simple sugar that is the
basic subunit of a carbohydrate.
• A single monosaccharide molecule contains three to
seven carbon atoms.
• Monosaccharide compounds are
• typically sweet-tasting
• white solids at room temperature
• water soluble
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates, continued
Monosaccharides, continued
• The most common
monosaccharides are
glucose (also called
dextrose) and fructose.
• Both have the formula
C6(H2O)6.
• Their structural formulas
differ.
Chapter 23
Section 1 Carbohydrates and Lipids
Structures of Carbohydrates
Chapter 23
Section 1 Carbohydrates and Lipids
Monosaccharides
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Visual Concept
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates, continued
Disaccharides
• A disaccharide is a sugar that consists of two
monosaccharide units that are joined together.
• sucrose, C12H22O11
• A molecule of sucrose forms when a glucose molecule
bonds to a fructose molecule.
• lactose
• Lactose is made up of a sugar called galactose and
glucose.
Chapter 23
Section 1 Carbohydrates and Lipids
Disaccharides
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Visual Concept
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates, continued
Carbohydrate Reactions
• Carbohydrates undergo two important kinds of
reactions: condensation reactions and hydrolysis
reactions.
• A condensation reaction is a reaction in which two
molecules or parts of the same molecule combine.
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates, continued
Carbohydrate Reactions, continued
• Hydrolysis is a chemical reaction between water
and another substance to form two or more new
substances.
• Disaccharides and longer-chain polysaccharides
can be broken down into smaller sugar units by
hydrolysis.
Chapter 23
Section 1 Carbohydrates and Lipids
Cation Hydrolysis
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Visual Concept
Chapter 23
Section 1 Carbohydrates and Lipids
Anion Hydrolysis
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Visual Concept
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates, continued
Polysaccharides
• When many monosaccharides or disaccharides
combine in a series of condensation reactions, they
form a polysaccharide.
• A polysaccharide is a carbohydrate made up of long
chains of simple sugars.
• Cellulose, starch, and glycogen are polymers of
glucose.
• Sheets of cellulose make up plant cell walls.
• Starch is the storage form of glucose in plants.
Chapter 23
Section 1 Carbohydrates and Lipids
Carbohydrates, continued
Polysaccharides, continued
• Glycogen, cellulose, and starch differ in their
arrangement of glucose monomers.
Chapter 23
Section 1 Carbohydrates and Lipids
Lipids
• A lipid is a type of biochemical that does not dissolve
in water, has a high percentage of C and H atoms,
and is soluble in nonpolar solvents.
• As a class, lipids are not nearly as similar to each
other as carbohydrates are.
• Long-chain fatty acids, phospholipids, steroids, and
cholesterol are lipids.
Chapter 23
Section 1 Carbohydrates and Lipids
Types of Lipids
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Visual Concept
Section 1 Carbohydrates and Lipids
Chapter 23
Lipids, continued
Fatty Acids and Triglycerides
• Fatty acids consist of a long, nonpolar hydrocarbon
“tail” and a polar carboxylic acid functional group at
the “head.”
• They have hydrophilic polar heads, but their
hydrocarbon chains make them insoluble in
water.
O
C
HO
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
hydrophilic region
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
hydrophobic region
H
Chapter 23
Section 1 Carbohydrates and Lipids
Lipids, continued
Fatty Acids and Triglycerides, continued
• Triglycerides are formed by condensation reactions in
which three fatty acid molecules bond to one glycerol (a
type of alcohol) molecule.
• Fats and oils that are the most common group of lipids in your
diet.
• Because they have a large amount of saturated fatty acids,
fats are solids at room temperature.
• Oils have more unsaturated fatty acids than fats, and are
liquids
• Fat is stored in adipose tissue until it is needed as an
energy source.
Chapter 23
Section 1 Carbohydrates and Lipids
Lipids, continued
Fatty Acids and Triglycerides, continued
• When a fat combines with NaOH, an acid-base reaction
called saponification occurs, and a salt and water
form.
• This salt is made up of molecules that have long
carboxylic acid chains and is called soap.
• Lipids that react with a base to form soap are called
saponifiable lipids, which include fats, oils, and fatty
acids.
Chapter 23
Section 1 Carbohydrates and Lipids
Lipids, continued
Other Important Lipids
• Compound saponifiable lipids play an important
role in biochemical processes.
• These lipids are structurally similar to triglycerides in that
at least one fatty acid is bonded to the central glycerol or
glycerol-like unit.
• These molecules may also have phosphate groups,
sugar units, or nitrogen containing groups.
• Phospholipids, are compound saponifiable lipids
and are the main structural component of cell
membranes.
Chapter 23
Section 1 Carbohydrates and Lipids
Lipids, continued
Other Important Lipids, continued
• Phospholipids are arranged in a bilayer, or double
layer, at the surface of the cell.
Chapter 23
Section 1 Carbohydrates and Lipids
Lipids, continued
Other Important Lipids, continued
• Nonsaponifiable lipids are nonpolar compounds that do
not form soap.
• steroids, many vitamins, and bile acids
• Cholesterol is a steroid present in animal cell
membranes and is a precursor of many hormones.
Chapter 23
Section 2 Amino Acids and Proteins
Preview
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Lesson Starter
Objectives
Amino Acids
Proteins
Proteins as Enzymes
Section 2 Amino Acids and Proteins
Chapter 23
Lesson Starter
O
• carboxylic acid
R–C–OH
• amine
R–N–R˝
R´
• condensation reaction to form dipeptide bond
R
H
N
C
H
H
R
OH
+
C
O
OH
H
N
C
H
H
R
H
C
N
O
H
R
C
C
N
C
H
O
H
H
+ H2O
OH
C
O
Chapter 23
Section 2 Amino Acids and Proteins
Objectives
• Describe the basic structure of amino acids and the
formation of polypeptides.
• Determine the significance of amino acid side chains
to the three-dimensional structure of a protein and
the function of a protein.
• Describe the functions of proteins in cells.
• Identify the effects of enzymes on biological
molecules.
Chapter 23
Section 2 Amino Acids and Proteins
• Amino acid molecules are the basic building blocks
of proteins.
• More than 700 types of amino acids occur in nature.
• Only 20 types of amino acids are found in human
proteins.
• The human body can synthesize only 11 of the 20
amino acids as needed.
• The other nine, called the essential amino acids,
have to be supplied by the food that we eat.
Section 2 Amino Acids and Proteins
Chapter 23
Amino Acids
• Amino acids are organic molecules that contain two
functional groups: a basic —NH2 amino group and an
acidic —COOH carboxylic acid group.
R
OH
H
N
C
H
H
R
or
C
O
H2N
C
COOH
H
• The R-groups of the amino acids present in a
protein determine the protein’s biological activity.
Chapter 23
Section 2 Amino Acids and Proteins
Structures of Amino Acids
Chapter 23
Section 2 Amino Acids and Proteins
Amino Acid
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Visual Concept
Chapter 23
Section 2 Amino Acids and Proteins
Amino Acids, continued
Amino Acid Reactions
• Two amino acids can react with each other in an acidbase reaction.
• The basic amino group of one amino acid reacts with
the acidic carboxylic acid group of another amino acid
to form a peptide, and a molecule of water is lost.
• This reaction is classified as a condensation
reaction
• The bond formed is called a peptide bond.
• The product is a dipeptide.
Chapter 23
Section 2 Amino Acids and Proteins
Formation of Dipeptides and Polypeptides
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Visual Concept
Section 2 Amino Acids and Proteins
Chapter 23
Amino Acids, continued
Amino Acid Reactions, continued
R
OH
H
N
C
N
N
O
H
R
H
C
C
H
O
H
OH
H
+
C
H
H
R
R
C
C
N
C
H
O
H
H
OH
+ H2 O
C
O
Chapter 23
Section 2 Amino Acids and Proteins
Amino Acids, continued
Amino Acid Reactions
• Longer chains of amino acids are called
polypeptides.
• Chains of 50 or more amino acids are called
proteins.
• Peptide bonds can be broken, or hydrolyzed, by
enzymes called proteases.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins
• Proteins are the most complex and varied class of
biochemical molecules.
• A protein is an organic biological polymer that is
made up of polypeptide chains of 50 or more amino
acids and is an important building block of all cells.
• Proteins are made up of specific sequences of amino acids.
• They have molecular masses that range from 6000 to more
than 9 million atomic mass units.
• About 9000 different protein molecules are found in
cells in the human body.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins
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Visual Concept
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
• Nitrogen accounts for about 15% of the mass of a
protein molecule. Most proteins also contain sulfur.
Some contain phosphorus or other elements, such as
iron, zinc, and copper.
• Proteins have many important catalytic, structural,
regulatory, and antibody defense functions.
• Keratin is the main component of hair and fingernails.
• Enzymes catalyze biochemical reactions.
• Hemoglobin carries oxygen in the blood.
• Insulin regulates glucose levels.
• Antibodies protect the body from foreign substances.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Arrangement of Amino Acids in Peptides and Proteins
• Each peptide, polypeptide, or protein is made up of a
special sequence of amino acids.
• A simple set of three-letter abbreviations is used to
represent each amino acid in these kinds of molecules.
• The tripeptide made up of valine, asparagine, and histidine
would be written as Val–Asp–His.
• Polypeptide and protein function depend not only on
the kinds and number of amino acids but also on
their order.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Amino Acid Side-Chain Reactions
• The properties of amino acids—and ultimately
polypeptides and proteins—depend on the
properties of the side chains present.
• The side chain of glutamic acid is acidic.
• The side chain of histidine is basic.
• The side chains of asparagine and several other amino
acids are polar.
• Some amino acid side chains can form ionic or covalent
bonds with other side chains.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Amino Acid Side-Chain Reactions, continued
• Cysteine is a unique amino acid, because the —SH
group in cysteine can form a covalent bond with
another cysteine side chain to form a disulfide bridge.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Shape and Structure of Protein Molecules
• The interaction of amino acid side chains determines
the shape and structure of proteins.
• These are important to the proteins’ biological
functions.
• In a polypeptide chain or protein, the sequence of the
amino acids is called the primary (1°) structure.
• The secondary (2°) structure describes how the chain
is coiled or otherwise arranged in space.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Shape and Structure of Protein Molecules, continued
• Secondary structures form because hydrogen
bonding occurs between a hydrogen atom attached to
the nitrogen atom in one peptide bond and the
oxygen atom of another peptide bond farther down
the backbone of the protein.
• The alpha (α) helix is a secondary structure that
resembles a coiled spring.
• The beta (β) pleated sheet is a secondary
structure that has accordion-like folds.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Shape and Structure of Protein Molecules, continued
• A protein’s characteristic three-dimensional shape is
called its tertiary (3°) structure.
• Side-chain interactions at various positions along
the protein backbone cause the tertiary structure.
• The side-chain interactions can include
• hydrogen bonding
• salt bridges
• cysteine-cysteine disulfide bonds
• hydrophobic interactions between nonpolar side chains
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Shape and Structure of Protein Molecules, continued
• Nonpolar side groups tend to be found in the interior
of the protein where contact with water is minimal.
• Polar and ionic side chains tend to be on the protein
surface, where they are in contact with water.
• In some proteins, different polypeptides, each of
which has its own 3° structure, come together.
• In the case of hemoglobin, four different
polypeptides make up the quaternary (4°)
structure.
Chapter 23
Section 2 Amino Acids and Proteins
Levels of Protein Structure
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Biological Functions of Proteins
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Biological Functions of Proteins, continued
• Fibrous proteins are insoluble in water and are long,
thin, and physically strong.
• Fibrous proteins give strength and protection to structures in
living things.
• Keratin has a secondary structure is almost entirely alpha
helical in shape.
• Collagen is a triple helix of three intertwined alpha helices. It
found in bone and tendons.
• Fibrin found in silk has a beta-pleated sheet structure.
• Elastins in blood tissue, fibrins in blood clots, and myosins
found in muscle tissue are other kinds of fibrous proteins.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Biological Functions of Proteins, continued
• Globular proteins are generally soluble in water and are
twisted and folded into a globe-like shape.
• Globular proteins regulate body functions, catalyze reactions,
and transport substances.
• Insulin is a small protein of 51 amino acids in two polypeptide
chains.
• Myoglobin transports oxygen in the muscles.
• Hemoglobin transports oxygen in the blood.
• Casein, found in milk and used for food. It contains
phosphorus, which is needed for bone growth.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins, continued
Amino Acid Substitution
• A single substitution of one amino acid for another can
change the shape and function of a protein.
• The genetic disease sickle cell anemia can happen
when glutamic acid—is replaced by valine.
Chapter 23
Section 2 Amino Acids and Proteins
Sickle Cell Anemia
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Visual Concept
Chapter 23
Section 2 Amino Acids and Proteins
Structures and Roles of Several Amino Acids
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes
• An enzyme is a protein that catalyzes a biochemical
reaction.
• Enzymes make up the largest and most highly
specialized class of proteins.
• Most enzymes are water-soluble, globular proteins.
• The amino acid side chains and the three-dimensional
shape of enzymes play a very important role in the
enzymatic activity.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
• An enzyme also does not change the amount of
product that is formed in a reaction; it only
decreases the time it takes to form the product.
• Enzymes catalyze both decomposition and
synthesis reactions.
• Enzymes are very efficient.
• A single molecule of carbonic anhydrase can break down
36 million carbonic acid molecules in 1 minute.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
Enzyme Specificity
• Enzymes are very specific and often catalyze just a
single reaction.
• Enzymes act by binding to a specific substrate
molecule.
• The shape of the enzyme is such that the substrate can
fit into the enzyme at a specific part of the enzyme
molecule, called the active site.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
Enzyme Specificity
• The resulting compound is called the enzyme-substrate
complex.
• This model of enzyme action is called the lock and key
model.
Chapter 23
Section 2 Amino Acids and Proteins
Enzyme Mechanism
Chapter 23
Section 2 Amino Acids and Proteins
Enzyme
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Visual Concept
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
Enzymes and Reaction Rates
• The presence of an enzyme in a chemical reaction can
increase the rate of a reaction by a factor of up to 1020.
• Only collisions that have enough energy to overcome
the activation energy and have the proper orientation
change reactants into products.
• Enzymes lower the activation energy by forming the
enzyme-substrate complex, which makes breaking
bonds in the reactants and forming new bonds in the
products easier.
Chapter 23
Section 2 Amino Acids and Proteins
Activation Energy With and Without an Enzyme
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
Temperature and Enzyme Activity
• Enzymes typically have
maximum activity within
a relatively narrow range
of temperatures.
• Enzymes in the human
body work optimally at
the normal body
temperature of 37°C
(98.6°F).
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
Temperature and Enzyme Activity
• High heat can denature, or alter, the shape of a protein,
which in turn alters the protein’s function.
• Denaturation is a change in a protein’s characteristic
three-dimensional shape due to changes of its
secondary, tertiary, and quaternary structure.
• example: cooking an egg
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
pH and Enzyme Activity
• The optimal pH for normal cell enzyme functions is
almost neutral, about 7.3 to 7.4.
• Changes in pH can cause changes in protein structure
and shape.
• Most enzymes become inactivated, or no longer work,
because of denaturation when the pH changes.
Chapter 23
Section 2 Amino Acids and Proteins
Proteins as Enzymes, continued
pH and Enzyme Activity, continued
• Pre-enzymes, inactive forms of protein-digesting
enzymes, become activated by the stomach’s low pH
of 1.5 to 2.0. This prevents the active form of the
enzymes from digesting the stomach lining.
• Pepsin is a stomach enzyme found in adults.
Chapter 23
Section 3 Metabolism
Preview
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Lesson Starter
Objectives
ATP: Energy for the Cell
Energy Activities
Catabolism
Anabolism
Chapter 23
Section 3 Metabolism
Lesson Starter
• What do you think metabolism is?
• How does your body obtain energy?
• Metabolism consists of all chemical reactions that
occur within an organism.
Chapter 23
Section 3 Metabolism
Objectives
• Describe the role of ATP in cells.
• Explain how energy is released by metabolic
reactions.
• Summarize the relationship between anabolism and
catabolism.
Chapter 23
Section 3 Metabolism
• Metabolism is the sum of all the chemical processes
that occur in an organism.
• Complex molecules are broken down into smaller
ones through catabolism.
• Simple molecules are used to build bigger ones
through a process called anabolism.
• A metabolic pathway is a series of linked chemical
reactions that occur within a cell and result in a
specific product.
Chapter 23
Section 3 Metabolism
ATP: Energy for the Cell
• Cells require energy to make the proteins,
carbohydrates, lipids, and nucleic acids that are
necessary for life.
• The original source for almost all of the energy
needed by living systems is the sun.
• Autotrophs, such as plants and photosynthetic
bacteria, use sunlight, water, and CO2 to make
carbon-containing biomolecules.
• This process is called photosynthesis.
Section 3 Metabolism
Chapter 23
Photosynthesis
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Visual Concept
Chapter 23
Section 3 Metabolism
ATP: Energy for the Cell, continued
• Photosynthesis occurs in the cells of plants and
algae, within structures called chloroplasts.
• Chloroplasts contain chlorophyll, an organic molecule
that absorbs solar energy.
• This energy is captured immediately in the bonds of
two compounds, one of which is adenosine
triphosphate (ATP).
Chapter 23
Section 3 Metabolism
Chlorophyll a and b
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Visual Concept
Chapter 23
Section 3 Metabolism
ATP: Energy for the Cell, continued
• ATP is a high-energy molecule that plant cells use to
make carbohydrates.
• The other compound, known as NADPH, is also used
in carbohydrate-forming reactions.
• Living things, including most microorganisms, which
depend on plants or other animals for food, are called
heterotrophs.
• Heterotrophs use the energy obtained in the breakdown of
complex molecules to drive chemical reactions in cells.
Chapter 23
Section 3 Metabolism
Linking Photosynthesis and Respiration
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Visual Concept
Chapter 23
ATP/ADP Cycle
Section 3 Metabolism
Chapter 23
Section 3 Metabolism
Energy Activities
• The cycle between ATP and ADP, adenosine
diphosphate, is the primary energy exchange
mechanism in the body.
• ATP is the molecule that serves to carry energy from
energy-storing molecules, carbohydrates, lipids, and
proteins to specific energy-requiring processes in
cells.
• When ATP is hydrolyzed to ADP, energy is released to
power the cell’s activities.
Chapter 23
Section 3 Metabolism
Comparing ADP and ATP
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Chapter 23
Section 3 Metabolism
Hydrolysis of ATP
Chapter 23
Section 3 Metabolism
Catabolism
• The energy that your body needs to maintain its
temperature and drive its biochemical reactions is
provided through catabolic processes.
• Catabolism is the part of metabolism in which
complex compounds break down into simpler ones
and is accompanied by the release of energy.
• First, enzymes break down the complex compounds
in food—carbohydrates, fats, and proteins—into
simpler molecules.
Chapter 23
Section 3 Metabolism
Catabolic Pathways
Chapter 23
Section 3 Metabolism
Catabolism, continued
• Carbohydrate digestion begins in the mouth, where
the enzyme amylase in saliva begins to break down
polysaccharides.
• Carbohydrates are broken down intoglucose and other
monosaccharides.
• Digestion of fats occurs only in the small intestine.
• Fats are broken down into fatty acids and glycerol.
• Protein digestion begins in the stomach and is
completed in the small intestine.
• Proteins are broken down into amino acids.
Chapter 23
Section 3 Metabolism
Catabolism, continued
• Once in the cells, glucose and other
monosaccharides, fatty acids, some amino acids, and
glycerol enter the mitochondria and feed into a
complex series of reactions called the citric acid
cycle, or Krebs cycle.
• The citric acid cycle produces carbon dioxide and
other molecules, such as NADH and ATP.
• This NADH and ATP then move through another set
of reactions to produce more ATP and water.
Chapter 23
Section 3 Metabolism
Energy Yield in Aerobic Respiration
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Visual Concept
Chapter 23
Section 3 Metabolism
Anabolism
• Cells use the simple molecules that result from the
breakdown of food to make larger, more complex
molecules.
• Anabolic processes are the energy-consuming
pathways by which cells produce the molecules that
they need for sustaining life and for growth and repair.
• The conversion of small biomolecules into larger ones
is called anabolism.
Chapter 23
Section 3 Metabolism
Anabolism, continued
• In an anabolic pathway, small precursor molecules
are converted into complex molecules, including
lipids, polysaccharides, proteins, and nucleic acids.
• Energy from ATP and NADH is necessary for these
biosynthesis reactions to occur.
• Catabolism and anabolism occur simultaneously.
• ATP and NADH serve as chemical “links” between the
two processes.
Chapter 23
Section 3 Metabolism
Anabolism, continued
• One important anabolic pathway that is common to
animals, plants, fungi, and microorganisms is
gluconeogenesis.
• Glucose is synthesized in this pathway from noncarbohydrate substances.
• In mammals, glucose from the blood is a fuel source.
Chapter 23
Section 3 Metabolism
Cellular Respiration
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Chapter 23
Section 4 Nucleic Acids
Preview
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Lesson Starter
Objectives
Nucleic Acid Structure
DNA: Deoxyribonucleic Acid
RNA: Ribonucleic Acid
Technology and Genetic Engineering
Chapter 23
Section 4 Nucleic Acids
Lesson Starter
• To understand how DNA replicates itself and passes
genetic information to RNA to make proteins, it is
important to understand hydrogen bonding.
• DNA does not duplicate itself by making an identical
DNA molecule.
• It replicates by unfolding its two strands, which then
pair up with complementary nucleotides.
• Each DNA molecule has one “new” strand and one
“original” strand that are complementary.
Chapter 23
Section 4 Nucleic Acids
Objectives
• Describe the role of ATP in cells.
• Explain how energy is released by metabolic
reactions.
• Summarize the relationship between anabolism and
catabolism.
Chapter 23
Section 4 Nucleic Acids
• Nucleic acids contain all of the genetic information of
an organism.
• They are the means by which a living organism
stores and conveys instructional information for all of
its activities.
• The two nucleic acids found in organisms are
• deoxyribonucleic acid (DNA)
• ribonucleic acid (RNA)
Chapter 23
Section 4 Nucleic Acids
Nucleic Acid Structure
• A nucleic acid is an organic compound, either RNA
or DNA, whose molecules carry genetic information
and is made up of one or two chains of monomer
units called nucleotides.
• A nucleotide molecule is composed of a five-carbon
sugar unit that is bonded to both a phosphate group
and a cyclic organic base containing nitrogen.
phosphate–sugar–phosphate–sugar
base
base
Chapter 23
Section 4 Nucleic Acids
Nucleic Acid
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
Nucleic Acid Structure
• The sugar unit in DNA is deoxyribose.
• The sugar unit in RNA is ribose.
• The five nitrogenous bases found in nucleic acids are
adenine (A), guanine (G), cytosine (C), thymine (T),
and uracil (U)
• Adenine (A), guanine (G), and cytosine (C) are found in
both DNA and RNA.
• Thymine (T) is found only in DNA.
• Uracil (U) is found only in RNA.
Chapter 23
Section 4 Nucleic Acids
Examples of Nucleotides
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
Nitrogenous Bases of Nucleic Acids
Chapter 23
Section 4 Nucleic Acids
DNA: Deoxyribonucleic Acid
• Every single instruction for all of the traits that you
have inherited and all of the life processes that occur
in your cells is contained in your DNA.
• Human cells contain 46 relatively large DNA
molecules.
• Each human cell contains about 2 m of DNA, which is
divided and packed into the cell’s 46 chromosomes.
Chapter 23
Section 4 Nucleic Acids
DNA Overview
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Chapter 23
Section 4 Nucleic Acids
DNA: Deoxyribonucleic Acid, continued
• DNA is a double helix. In this structure, two strands of
the sugar-phosphate backbone are wound around
each other, and the nitrogenous bases point inward.
• The sequence of these nitrogenous bases along the
phosphate-sugar backbone in DNA forms the code
responsible for transferring genetic information.
• Hydrogen bonding between pairs of A—T (adeninethymine) or G—C (guanine-cytosine) bases makes
the double helix stable.
Chapter 23
Section 4 Nucleic Acids
Structure of DNA
Chapter 23
Section 4 Nucleic Acids
DNA: Deoxyribonucleic Acid, continued
Nitrogenous Base Pairs
• In the DNA double helix, base pairing exists only
between A—T and between C—G.
• The interaction between base pairs accounts for the
ability of DNA to replicate itself.
• Combinations of the four-letter alphabet of A,T,G, and
C form the genes that define our heredity.
• Each gene is a section of DNA that contains a specific
sequence of four bases (A,G,T, and C) and typically
contains about 1000 to 2000 base pairs.
Chapter 23
Section 4 Nucleic Acids
Hydrogen Bonding in DNA
Chapter 23
Section 4 Nucleic Acids
Gene
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
DNA: Deoxyribonucleic Acid, continued
DNA Replication
• The two strands of the double helix of DNA are not
identical.
• A base on one strand is paired through hydrogen bonding to
its complementary base on the other strand.
• Each time a cell divides, an exact copy of the DNA of
the parent cell is reproduced for the daughter cells.
• The process by which an identical copy of the original
DNA is formed is called DNA replication.
Chapter 23
Section 4 Nucleic Acids
DNA Replication
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Chapter 23
Section 4 Nucleic Acids
DNA Replication
Chapter 23
Section 4 Nucleic Acids
Ribonucleic Acid (RNA)
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Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid
•
Molecules of RNA make up about 5% to 10% of the
mass of a cell.
•
RNA molecules are responsible for the synthesis of
proteins.
•
RNA differs from DNA in four basic ways:
1. the sugar unit in the backbone of RNA is ribose
rather than deoxyribose
2. RNA contains the base uracil, U, instead of
thymine, which occurs in DNA
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
3. RNA is a single-stranded molecule rather than
a double-stranded helix like DNA
4. RNA molecules typically consist of 75 to a few
thousand nucleotide units rather than the
millions that exist in DNA.
•
It is not uncommon for up to 50% of an RNA
molecule to have a double-helix structure.
•
The base sequences along the helical regions of the
RNA strand are complementary.
Chapter 23
Section 4 Nucleic Acids
Comparing DNA and RNA
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
Synthesis of RNA
• RNA is synthesized in the nucleus of the cell
• DNA and protein molecules actually help
synthesize specific RNA molecules.
• As RNA is synthesized, the information contained in
the DNA is transferred to the RNA molecules.
• The genetic information of RNA is carried in its
nucleotide sequence.
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
Synthesis of RNA, continued
• One type of RNA molecule is called messenger RNA
(mRNA) because it carries the instructions for making
proteins out into the cytosol, where proteins are
produced on ribosomes.
• A ribosome is a cell organelle that is composed of
RNA and protein. Ribosomes are the main site of
protein production in cells.
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
Synthesis of RNA, continued
• The DNA template is also used to make two other types
of RNA molecules: ribosomal RNA (rRNA) and transfer
RNA (tRNA).
• Both of these types of RNA also leave the nucleus and come
together in the ribosome where they help synthesize proteins.
• Ribosomal RNA becomes part of the structure of the ribosome.
• Transfer RNA is used to transfer amino acids into the
ribosome.
• Only mRNA carries the coded genetic information that is
translated into proteins.
Chapter 23
Section 4 Nucleic Acids
Types of RNA
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
Synthesis of RNA, continued
• The portion of DNA that holds the specific genetic
code for a single, specific mRNA molecule is a gene.
• Each gene is typically a section of the DNA chain that
contains about 1000 to 2000 nucleotides.
• A gene has the information necessary in this
sequence to direct RNA to produce several proteins
that have specific functions.
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
RNA and Protein Synthesis
• At a gene, a portion of DNA unwinds and RNA is
assembled using the same complementary base pairs
as DNA except that uracil replaces the thymine
• As in DNA replication, the RNA sequence that forms
has the complementary base pairs of the DNA gene.
DNA strand: C C C C A C C C T A C G G T G
RNA strand: G G G G U G G G A U G C C A C
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
RNA and Protein Synthesis
• A sequence of three bases in mRNA codes for a
specific amino acid.
• The sequence CAG codes for glutamic acid.
• The sequence GUC codes for valine.
• There are 64 (43) unique combinations of threebase sequences made from four bases.
• Because only 20 amino acids require codes, some
of the amino acids have more than one code.
Chapter 23
Section 4 Nucleic Acids
RNA: Ribonucleic Acid, continued
RNA and Protein Synthesis
• The genetic code is universal.
• The “stop” signal in the gene is also a three-base
code: UAG, UAA, or UGA.
Chapter 23
Section 4 Nucleic Acids
Genetic Code
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Chapter 23
Section 4 Nucleic Acids
Using the Genetic Code
Chapter 23
Section 4 Nucleic Acids
Technology and Genetic Engineering
• Scientists in the field of genetic engineering study
how manipulation of an organism’s genetic material
can modify the proteins that are produced and the
changes that result in the organism.
• Today genetic engineering refers to recombinant DNA
technology that is used for cloning and the creation of
new forms of life.
Chapter 23
Section 4 Nucleic Acids
Genetic Engineering
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
Technology and Genetic Engineering, continued
DNA Fingerprinting
• DNA is unique to an individual except for identical
twins.
• This technology is used in criminal investigations,
paternity testing, and victim identification.
• The technique of the polymerase chain reaction
(PCR) may be used to copy a DNA sample to supply
sufficient DNA for identification.
Section 4 Nucleic Acids
Chapter 23
DNA Fingerprint
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
Making a DNA Fingerprint
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
Polymerase Chain Reaction
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
Technology and Genetic Engineering, continued
Cloning
• Cloning is the process of making an exact copy of an
organism.
• Artificial cloning, using stem cells from animals or
meristem cells from plants, can produce identical
replicas of the parent cells or, under specialized
conditions, a complete organism that is identical to
the original organism.
Chapter 23
Section 4 Nucleic Acids
Cloning
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Visual Concept
Chapter 23
Section 4 Nucleic Acids
Technology and Genetic Engineering, continued
Recombinant DNA Technology
• Recombinant DNA technology has been used to
insert DNA from one organism into another.
• The technique splices a gene from one organism’s
DNA into a molecule of DNA from another organism.
• When the spliced DNA is inserted into a cell, the cell
is able to make the protein that is coded by the
spliced gene.
Chapter 23
Section 4 Nucleic Acids
Using Plasmids to Produce Insulin
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Visual Concept
End of Chapter 23 Show