CHAPTER 3
Proteins, Carbohydrates, and Lipids
2
BIOLOGY II
Development, Structure
and function of organisms
(BIOL 131)
1
CHAPTER 3
Proteins, Carbohydrates, and Lipids
2
Chapter 3: Proteins, Carbohydrates, and
Lipids
Key Concepts
3.1 Macromolecules Characterize Living Things Pages: 44-46
3.2 Proteins Are Polymers with Highly Variable Structures Pages: 46-56
3.3 Carbohydrates Are Made from Simple Sugars Pages: 57-61
3.4 Lipids Are Defined by Their Insolubility in Water Pages: 61-64
Investigating LIFE introduction
Weaving a Web
•Spider silk is composed of proteins and is extremely strong.
•The protein molecules in different types of silk have different
structural characteristics and functions.
Q&A: What are practical uses for spider silk?
(See slides 9–10 and 50.)
Chapter 3, section 3.1, Page 43
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Concept 3.1 Macromolecules Characterize Living Things
Molecules that make up
organisms:
• Proteins
• Carbohydrates
• Lipids
• Nucleic acids
Figure 3.3 Substances Found in Living Tissues
All except lipids are polymers of smaller molecules called monomers.
Chapter 3, section 3.1, Page 44
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Concept 3.1 Macromolecules Characterize Living Things
Functional chemical groups determine the structures of
macromolecules
Macromolecules: Polymers containing
thousands or more atoms. (Large lipids
are also treated as macromolecules.)
- Macromolecule function depends on the
properties of functional groups. Each
group has specific properties, such as
polarity.
Chapter 3, section 3.1, Page 44
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Concept 3.1 Macromolecules Characterize Living Things
Functional chemical groups determine the structures of
macromolecules
Macromolecules: Polymers containing
thousands or more atoms. (Large lipids
are also treated as macromolecules.)
- A single macromolecule may contain
many different functional groups.
Chapter 3, section 3.1, Page 44
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Concept 3.1 Macromolecules Characterize Living Things
The structures of macromolecules reflect their functions
Isomers: Molecules with the same
chemical formula, but the atoms are
arranged differently.
• Structural isomers differ in how atoms
are joined
• cis-trans isomers: different orientation
around a double bond
• Optical isomers: mirror images
Chapter 3, section 3.1, Pages 45-46 Figure 3.2 Isomers
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Investigating LIFE introduction
Weaving a Web
•Spider silk is composed of proteins and is extremely strong.
•The protein molecules in different types of silk have different
structural characteristics and functions.
Q&A: What are practical uses for spider silk?
(See slides 9–10 and 50.)
Chapter 3, section 3.1, Page 43
4
Concept 3.1 Macromolecules Characterize Living Things
Investigating LIFE: Making Spider Silk (1 of 2)
Hypothesis: Genetically engineered silkworms can produce silk with
properties like silk made by spiders.
Method:
• Extract silk fibers produced by spiders and genetically engineered
silkworms.
• Measure tensile strength of fibers by stretching them on an analyzer.
Chapter 3, section 3.1, Page 46
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Concept 3.1 Macromolecules Characterize Living Things
Chapter 3, section 3.1, Page 47
Investigating LIFE: Making Spider Silk (2 of 2)
Results: Both silks had identical physical properties of stress and strain.
Conclusion: Silkworms can make composite silk fiber with the same
properties as those of the native spider silk protein.
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Concept 3.1 Macromolecules Characterize Living Things
Most macromolecules are formed by condensation and
broken down by hydrolysis
Condensation reactions:
energy is used to make
covalent bonds between
monomers to make a polymer;
a water molecule is removed.
Hydrolysis reactions: polymers
are broken down into
monomers; energy is released
and water is consumed.
Figure 3.4 Condensation and Hydrolysis of Polymers (Part 1)
Chapter 3, section 3.1, Page 46
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Concept 3.1 Macromolecules Characterize Living Things
Most macromolecules are formed by condensation and
broken down by hydrolysis
Condensation reactions:
energy is used to make
covalent bonds between
monomers to make a polymer;
a water molecule is removed.
Hydrolysis reactions: polymers
are broken down into
monomers; energy is released
and water is consumed.
Figure 3.4 Condensation and Hydrolysis of Polymers (Part 2)
Chapter 3, section 3.1, Page 46
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Key Concept 3.1, Question 1
Key Concept 3.1, Question 1
Hydroxyl groups are polar, and thus a molecule that
contains multiple hydroxyl groups will be
a. basic.
b. soluble in water.
c. involved in reactions forming more complex molecules.
d. hydrophobic.
Key Concept 3.1, Question 3
Cis and trans isomers
a. have similar properties despite opposite orientations in
structure.
b. have the same structure, but the cis form has an extra
double bond.
c. have the same structure, but the trans form has an extra
double bond.
d. are mirror images of each other in structure.
e. are centered around a double bond with atoms on either
side in different orientations with respect to each other.
Concept 3.2 Proteins Are Polymers with Highly Variable Structures
- Proteins consist of one or more polypeptide chains—single,
unbranched chains of amino acids.
- The chains are folded into specific 3-D shapes as defined by
the sequence of amino acids.
- Proteins have diverse functions.
Chapter 3, section 3.2, Pages 46 and 48
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Chapter 3, section 3.2, Page 48
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Monomers of proteins link together to make the
macromolecule
Amino acids have carboxyl and amino
groups—they function as both acid and
base.
Side chains or R-groups also have
functional groups. Amino acids are grouped
based on the side chains.
The α carbon is asymmetrical; amino acids
can be optical isomers: D- and L-amino
acids.
Chapter 3, section 3.2, Page 48 Figure 3.5 An Amino Acid 15
Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Chapter 3, section 3.2, Page 49
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Chapter 3, section 3.2, Page 49
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Chapter 3, section 3.2, Page 49
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Chapter 3, section 3.2, Page 49
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Disulfide bridge formation
Cysteine:
The terminal —SH group can react with
another cysteine side chain to form a
disulfide bridge, or disulfide bond (—
S—S—).
These are important in protein folding but
most cysteines in a protein are not
involved in disulfide bridges.
Chapter 3, section 3.2, Page 49 Figure 3.6 A Disulfide Bridge
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Peptide bonds form the backbone of a protein
Oligopeptides, or peptides:
short polymers of 20 or fewer
amino acids.
Polypeptides: longer polymers.
Amino acids bond together
covalently in a condensation
reaction by peptide linkages
(peptide bonds).
Chapter 3, section 3.2, Page 50
Figure 3.7 Peptide Bond Formation
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The primary structure of a protein is its amino acid
sequence
Primary structure of a protein: the sequence of amino acids.
- Properties of side chain functional groups determine how the protein
can twist and fold; determines secondary and tertiary structure.
- The number of different proteins that can be made from 20 amino
acids is enormous!
KETAAAKFERQHMDSSTSAA
Chapter 3, section 3.2, Page 50
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The secondary structure of a protein requires
hydrogen bonding
Secondary structure:
α helix—right-handed coil resulting from hydrogen bonding between N–H groups and C=O groups.
β pleated sheet—two or more polypeptide chains are aligned; hydrogen bonds form between the
chains.
Chapter 3, section 3.2, Pages 51-52 Figure 3.8 The Four Levels of Protein Structure (part 1) 23
Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The secondary structure of a protein requires
hydrogen bonding
Secondary structure:
α helix—right-handed coil resulting from hydrogen bonding between N–H groups and C=O groups.
β pleated sheet—two or more polypeptide chains are aligned; hydrogen bonds form between the
chains.
Chapter 3, section 3.2, Pages 51-52 Figure 3.8 The Four Levels of Protein Structure (part 2) 24
Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The secondary structure of a protein requires
hydrogen bonding
Secondary structure:
α helix—right-handed coil resulting from
hydrogen bonding between N–H
groups and C=O groups. Figure 3.9 Left- and
Right-Handed Helices
β pleated sheet—two or more
polypeptide chains are aligned;
hydrogen bonds form between the
chains.
Chapter 3, section 3.2, Pages 51-52
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The tertiary structure of a protein is formed by
bending and folding
Tertiary structure: Folding
results in the specific 3-D
shape.
Determined by
interactions between R-
groups (disulfide bonds,
hydrogen bonds, etc.).
The outer surfaces present
functional groups that can Figure 3.8 The Four Levels of Protein Structure (part 3)
interact with other
molecules. Chapter 3, section 3.2, Pages 51-53
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The tertiary structure of a protein is formed by bending and folding
Chapter 3, section 3.2, Pages 97-99
Figure 3.10 Three Representations of Lysozyme Chapter 3, section 3.2, Pages 51-53 27
Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The tertiary structure of a protein is formed by bending and folding
If a protein is heated, secondary and
tertiary structure break down; the
protein is said to be denatured.
When cooled, some proteins return to
normal tertiary structure, demonstrating
that the information to specify protein
shape is in the primary structure.
Chapter 3, section 3.2, Pages 51-53
Figure 3.11A (1) Primary Structure Specifies Tertiary Structure (Experiment) 28
Concept 3.2 Proteins Are Polymers with Highly Variable Structures
The quaternary structure of a protein consists of subunits
- Many proteins have two or more polypeptide chains, or subunits.
- Quaternary structure results from interaction of subunits by hydrophobic
interactions, van der Waals forces, ionic attractions, and hydrogen bonds.
- Each subunit has its own unique tertiary structure.
Chapter 3, section 3.2, Page 51 and 53 Figure 3.8 The Four Levels of Protein Structure (part 4) 29
Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Shape and surface chemistry contribute to protein function
- Proteins bind noncovalently with
specific molecules. Specificity is
determined by:
• Shape—there must be a general
“fit” between the protein and the
other molecule.
• Chemistry—surface R groups
interact with other molecules via
ionic, hydrophobic, or hydrogen
Figure 3.12 Quaternary Structure of a Protein
bonds.
Chapter 3, section 3.2, Pages 53-54
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Environmental conditions affect protein structure
- Proteins bind noncovalently with
specific molecules. Specificity is
determined by:
Figure 3.13 Noncovalent
• Shape—there must be a general Interactions between
“fit” between the protein and the Proteins and Other
other molecule. Molecules
• Chemistry—surface R groups
interact with other molecules via
ionic, hydrophobic, or hydrogen
bonds.
Chapter 3, section 3.2, Pages 53-54
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Concept 3.2 Proteins Are Polymers with Highly Variable Structures
Protein shape can change
Protein shape can change as a
result of:
• Interaction with other
molecules—for example, an
enzyme changes shape
when it comes into contact
with a reactant.
• Covalent modification—
addition of a chemical group,
such as a phosphate, to an Figure 3.14 Protein Structure Can Change
amino acid.
Chapter 3, section 3.2, Page 55 32
Protein can change its shape as a result of:
interaction with other molecules or by covalent modifications
Key Concept 3.2, Question 1
When amino acids link together to form a polypeptide,
the peptide bonds that form are between
a. a phosphate group and a hydroxyl group.
b. R groups.
c. the two peptide chains of a protein dimer.
d. an amino group and a carboxyl group.
e. sulfhydryl groups.
Concept 3.3 Carbohydrates Are Made from Simple Sugars
Carbohydrates: (C1H2O1)n.
Chapter 3, section 3.3, Page 57
• Sources of stored energy
• Used to transport stored energy
• Carbon skeletons for many other molecules
• Form extracellular structures such as cell walls
- Monosaccharides: Simple sugars.
- Disaccharides: Two simple sugars linked by covalent bonds.
- Oligosaccharides: 3 to 20 monosaccharides.
- Polysaccharides: Hundreds or thousands of monosaccharides.
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Carbohydrates make up a large group of molecules that all have similar atomic compositions but differ
greatly in size, chemical properties, and biological functions.
Carbohydrates have four major biochemical roles:
There are four categories of biologically important carbohy-drates, defined by the number of
monomers:
Concept 3.3 Carbohydrates Are Made from Simple Sugars
Monosaccharides are simple sugars
All cells use glucose as an energy source.
Exists as a straight chain or ring form (more stable).
Ring form exists as α- or β-glucose, which can interconvert.
Chapter 3, section 3.3, Pages 57-58
Chapter
Figure 3, section
3.16 From3.3,
OnePage
Form103
of Glucose to the Other
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Concept 3.3 Carbohydrates Are Made from Simple Sugars
Monosaccharides are simple sugars
Monosaccharides:
• Pentoses: five-carbon
sugars; includes ribose and
deoxyribose in RNA and DNA
• Hexoses: six-carbon sugars;
some are structural isomers.
Chapter 3, section 3.3, Pages 57-58
Figure 3.17 Monosaccharides Are Simple Sugars
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Concept 3.3 Carbohydrates Are Made from Simple Sugars
Glyosidic bonds link Monosaccharides
- Monosaccharides bind together in
condensation reactions to form
glycosidic bonds to form
disaccharides.
- Oligosaccharides: several
monosaccharides linked by
glycosidic bonds; often covalently
bonded to proteins and lipids on
cell surfaces, where they serve as
recognition signals.
Chapter 3, section 3.3, Pages 58-59
Figure 3.18 Disaccharides Form by Glycosidic Bonds
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Monosaccharides bind together in condensation reactions to form
to form disaccharides.
often covalently bonded to proteins and lipids on cell surfaces,
where they serve as recognition signals
Concept 3.3 Carbohydrates Are Made from Simple Sugars
Polysaccharides store energy and provide structural materials
Polysaccharides are large polymers of monosaccharides
connected by glycosidic bonds; some are branched.
• Starch: storage of glucose in plants
• Glycogen: storage of glucose in animals
• Cellulose: very stable, good for structural components
Chapter 3, section 3.3, Pages 58-59 Figure 3.19 Representative Polysaccharides 37
Polysaccharides store energy and provide structural materials
Starches make up a family of large molecules with sim- ilar structures.
water-insoluble, highly branched
polymer of glucose.
It is used to store glucose in the liver and muscles and is thus an energy
storage compound for animals, as starch is for plants.
Concept 3.3 Carbohydrates Are Made from Simple Sugars
Polysaccharides store energy and provide structural materials
Figure 3.19 Representative Polysaccharides
Chapter 3, section 3.3, Pages 58-59 38
Concept 3.3 Carbohydrates Are Made from Simple Sugars
Chemically modified carbohydrates contain additional
functional groups
Carbohydrates can be
modified by the addition
of functional groups to
form:
• Sugar phosphates
• Amino sugars
• Chitin
Chapter 3, section 3.3, Pages 60-61
Figure 3.20 Chemically Modified Carbohydrates
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Chemically modified carbohydrates contain additional
functional groups
Carbohydrates can be modified by the addition of functional groups to
form:
Key Concept 3.3, Question 1
Carbohydrates
a. are a store of genetic information.
b. are the main structure of the plasma membrane.
c. are a base from which other molecules can be
made.
d. cannot be chemically modified.
e. aid in the folding of proteins.
Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Lipids
Lipids are nonpolar hydrocarbons; insoluble in water.
If close together, weak but additive van der Waals forces hold
them together in aggregates.
Types of lipids:
• Fats and oils store energy.
• Phospholipids—structural role in cell membranes.
• Carotenoids and chlorophylls—capture light energy in plants.
Chapter 3, section 3.4, Page 61
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Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Lipids
Lipids are nonpolar hydrocarbons; insoluble in water.
If close together, weak but additive van der Waals forces hold them together in aggregates.
Types of lipids:
• Fats and oils store energy.
• Phospholipids—structural role in cell membranes.
• Carotenoids and chlorophylls—capture light energy in plants.
• Steroids and modified fatty acids—hormones and vitamins.
• Animal fat—thermal insulation.
• Lipid coating around nerves provides electrical insulation.
• Oil and wax on skin, fur, and feathers repel water and slows evaporation.
Chapter 3, section 3.4, Page 61 41
If close together, weak but additive van der Waals forces hold
them together in aggregates.
Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Fats and oils are triglycerides
Fats and oils are triglycerides:
three fatty acids plus glycerol.
Fatty acid: Nonpolar
hydrocarbon chain with a polar
carboxyl group.
• Carboxyls bond with
hydroxyls of glycerol in ester
linkages (condensation
reactions).
Chapter 3, section 3.4, Page 61
Figure 3.21 Synthesis of a Triglyceride
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Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Fats and oils are triglycerides
Saturated fatty acid: No double
bonds between carbons—it is
saturated with H atoms (animal
fats; solid at room temperature).
Unsaturated fatty acid: One or
more double bonds in the carbon
chain result in kinks that prevent
packing (plant oils; liquid at room
temperature).
Chapter 3, section 3.4, Pages 61-63
Figure 3.22 Saturated Fatty Acids
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Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Fats and oils are triglycerides
Saturated fatty acid: No double
bonds between carbons—it is
saturated with H atoms (animal
fats; solid at room temperature).
Unsaturated fatty acid: One or
more double bonds in the carbon
chain result in kinks that prevent
packing (plant oils; liquid at room
temperature).
Chapter 3, section 3.4, Pages 61-63
Figure 3.22 Saturated Fatty Acids
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result in kinks that prevent
packing (plant oils; liquid at room
temperature)
Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Fats and oils are triglycerides
Double bonds in naturally occurring
unsaturated fats are cis (H atoms are on
the same side).
Trans fats: H atoms are on opposite
sides of the C=C bond (trans).
Trans fats result from hydrogenation of
vegetable oils to produce a saturated
fat (e.g. for margerine), but some of the
cis bonds convert to trans.
Chapter 3, section 3.4, Pages 61-63
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Double bonds in naturally occurring
unsaturated fats are cis (H atoms are on
the same side).
Trans fats result from hydrogenation of
vegetable oils to produce a saturated
fat (e.g. for margerine), but some of the
cis bonds convert to trans
Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Fats and oils are triglycerides
Trans fats may contribute to
heart disease and stroke.
Omega-3 fatty acids protect
against heart disease and
stroke. The first C=C bond is
at position 3 in the fatty acid
chain.
Chapter 3, section 3.4, Pages 61-63
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Trans fats may contribute to
heart disease and stroke
The first C=C bond is at position 3 in the fatty acid chain
Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Phospholipids form biological membranes
Phospholipids: Fatty acids
bound to glycerol; a phosphate
group replaces one fatty acid.
They are amphipathic:
• “Head” is a phosphate
group—hydrophilic.
• “Tails” are fatty acid chains—
hydrophobic.
Chapter 3, section 3.4, Pages 63-64
Figure 3.23a Phospholipids
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They are amphipathic:
•
“Head” is a phosphate
group—hydrophilic.
•
“Tails” are fatty acid chains—
hydrophobic
Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Phospholipids form biological membranes
Bilayer: In water, phospholipids line
up with the hydrophobic tails
together and the phosphate heads
facing outward.
Biological membranes have this kind
of phospholipid bilayer structure.
In animals, phospholipids and
proteins form lipoproteins which Figure 3.23b&c Phospholipids
transport lipids such as cholesterol
in the blood.
Chapter 3, section 3.4, Pages 63-64
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: In water, phospholipids line
up with the hydrophobic tails
together and the phosphate heads
facing outward.
Biological membranes have this kind
of phospholipid bilayer structure
In animals, phospholipids and
proteins form lipoproteins which
transport lipids such as cholesterol
in the blood
Concept 3.4 Lipids Are Defined by Their Insolubility in Water
Some lipids have roles in energy conversion, regulation and protection
Carotenoids: light-absorbing
pigments, e.g., β-carotene traps
light energy for photosynthesis. In
humans, β-carotene breaks down
into Vitamin A.
Steroids: Multiple rings share
carbons. Cholesterol is important in
membranes; other steroids are
hormones.
Waxes: long-chain alcohol bound to
an unsaturated fatty acid.
Chapter 3, section 3.4, Page 64 Figure 3.24 More Lipids
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Some lipids have roles in energy conversion, regulation and protection
Carotenoids: light-absorbing
pigments, e.g., β-carotene traps
light energy for photosynthesis. In
humans, β-carotene breaks down
into Vitamin A.
Waxes: long-chain alcohol bound to
an unsaturated fatty acid
Steroids: Multiple rings share
carbons. Cholesterol is important in
membranes; other steroids are
hormones.
Chapter 3 Proteins, Carbohydrates, and Lipids
Investigating LIFE conclusion
Q&A: What are practical uses of spider silk?
• Composite silkworm–spider silk is now available in industrial
quantities.
• Applications include surgical sutures, bullet-proof vests, and
textiles.
Chapter 3, Page 65
50
Key Concept 3.4, Question 1
Which substance is likely to contain the highest
percentage of double bonds in the hydrocarbon
chains of its triglycerides?
a. Butter
b. saturated fat
c. Olive oil
d. Beef fat
Which substance is likely to contain the highest percentage of double bonds in the
hydrocarbon chains of its triglycerides?
a. Butter
b. saturaded fat
c. Olive oil
d. Beef fat
Name this process? -condensation reaction
The name of the product molecule?-triglyceride
What is the name of the formed bond? -Easter bond
Is this molecule solid or liquid? -solid
The importance of this molecule. -regulatory function
The monomer of this molecule is? -glucose
The name of this polymer in plants? -starch
The main glycosidic bond in the chain?-alpha 1-4
What is the branching point? -alpha 1-6
The importance of this molecule -energy storage
