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Chapter 3
Lecture
Slides
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3.1 Polymers Are Built of
Monomers
• Organic molecules make up the bodies
of living organisms
 have a carbon-based core
 the core has attached groups of atoms called
functional groups
• the functional groups confer specific chemical
properties on the organic molecules
Figure 3.2 Five principal functional groups
3.1 Polymers Are Built of
Monomers
•
The building materials of the body are known as
macromolecules because they can be very large
•
There are four types of macromolecules:
1.
2.
3.
4.
•
Proteins
Nucleic acids
Carbohydrates
Lipids
Macromolecules are actually assembled from many
similar small components, called monomers

the assembled chain of monomers is known as a polymer
3.1 Polymers Are Built of
Monomers
• All macromolecules are assembled the same
way
 a covalent bond is formed between two subunits by
removing a hydroxyl group (OH) from one subunit and
a hydrogen (H) from another subunit
 because this amounts to the removal of a molecule of
water (H2O), this process is called dehydration
synthesis
Figure 3.4(a) Dehydration
synthesis
3.1 Polymers Are Built of
Monomers
• The process of disassembling polymers
into component monomers is essentially
the reverse of dehydration synthesis
 a molecule of water is added to break the
covalent bond between the monomers
 this process is known as hydrolysis
Figure 3.4(b) Hydrolysis
3.2 Proteins
• Proteins are complex macromolecules that
are polymers of many subunits called
amino acids
Figure 3.3(a) Polymers are built of monomers: protein
3.2 Proteins
•
Amino acids are small molecules with a
simple basic structure, a carbon atom to
which three groups are added
•
•
•
•
an amino group (-NH2)
a carboxyl group (-COOH)
a functional group (R)
The functional group gives amino acids
their chemical identity

there are 20 different types of amino acids
Figure 3.6 Basic structure of an amino acid
Animation: Limiting Amino Acids
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3.2 Proteins
• The covalent bond linking two amino
acids together is called a peptide
bond
• The assembled polymer is called a
polypeptide
Figure 3.7 The formation of the peptide bond
3.2 Proteins
• Protein structure is complex
 the order of the amino acids that form the polypeptide
affects how the protein folds together
 the way that a polypeptide folds to form the protein
determines the protein’s function
• some proteins are comprised of more than one polypeptide
3.2 Proteins
•
There are four general levels of protein
structure
1. Primary structure
2. Secondary structure
3. Tertiary structure
4. Quaternary structure
3.2 Proteins
• Primary structure –
the sequence of
amino acids in the
polypeptide chain
• This determines all
other levels of protein
structure
Figure 3.8 Levels of protein
structure: primary structure
3.2 Proteins
• Secondary structure – the
initial folding of the amino
acid chains
• Occurs because regions of
the polypeptide that are nonpolar are forced together
• The folded structure may
resemble coils, helices, or
sheets
Figure 3.8 Levels of protein
structure: secondary structure
3.2 Proteins
• Tertiary structure –
the final 3-D shape of
the protein
• The final twists and
folds that lead to this
shape are the result
of polarity differences
in regions of the
polypeptide
Figure 3.8 Levels of protein
structure: tertiary structure
3.2 Proteins
• Quaternary
structure – the
spatial arrangement
of component
polypeptides in
proteins comprised
of more than one
polypeptide chain
Figure 3.8 Levels of protein
structure: quaternary structure
4.2 Protein
• Changes to the environment of the protein
may cause it to unfold or denature
 increased temperature or lower pH affects
hydrogen bonding, which is involved in the
folding process
 a denatured protein is inactive
Figure 3.9 Protein denaturation
Animation: Protein Denaturation
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4.2 Proteins
• The shape of a protein affects its function
 proteins that serve architectural and structural
roles are often long and cable-like
 Proteins that act as enzymes are globular,
having a special 3-D shape that fits precisely
with another chemical
• they cause the chemical that they fit with to
undergo a reaction
Figure 3.10 Protein structure
determines function
3.3 Nucleic Acids
•
Nucleic acids are very long polymers
that store information

comprised of monomers called nucleotides
Figure 3.3(b) Polymers are built of monomers: nucleic acid
3.3 Nucleic Acids
•
Each nucleotide has 3 parts
1. a five-carbon sugar
2. a phosphate group
3. an organic nitrogen-containing base

there are five different types of nucleotides
•
information is encoded in the nucleic acid by
different sequences of these nucleotides
Figure 3.11
The structure
of a nucleotide
3.3 Nucleic Acids
• There are two types of nucleic acids
 Deoxyribonucleic acid (DNA)
 Ribonucleic acid (RNA)
• RNA is similar to DNA except that
 it uses uracil instead of thymine
 it is comprised of just one strand
 it has a ribose sugar
Figure 3.12 How DNA structure
differs from RNA
3.3 Nucleic Acids
• The structure of DNA is a double helix
because
 there are only two base pairs possible
• Adenine (A) pairs with thymine (T)
• Cytosine (C) pairs with Guanine (G)
 the bonds holding together a base pair are
hydrogen bonds
 a sugar-phosphate backbone comprised of
phosphodiester bonds gives support
Figure 3.13
The DNA
double helix
3.3 Nucleic Acids
• The structure of DNA helps it to function
 the hydrogen bonds of the base pairs can be broken
to unzip the DNA so that information can be copied
• each strand of DNA is a mirror image so the DNA contains
two copies of the information
 having two copies means that the information can be
accurately copied and passed to the next generation
3.4 Carbohydrates
• Carbohydrates are used for energy or
sometimes as structural molecules
 a carbohydrate is any molecule that contains the
elements C, H, and O in a 1:2:1 ratio
 the sizes of carbohydrates varies
• simple carbohydrates – made up of one or two monomers
• complex carbohydrates – long polymers
Figure 3.3(c)
Polymers are built of
monomers:
carbohydrate
3.4 Carbohydrates
• Simple carbohydrates are small
 monosaccharides consist of only one monomer
subunit
• an example is the sugar glucose (C6H12O6)
 disaccharides consist of two monosaccharides
• an example is the sugar sucrose, which is formed by joining
together two monosaccharides, glucose and fructose
Figure 3.14 The structure of glucose
3.4 Carbohydrates
• Complex carbohydrates are long
polymer chains
 because they contain many C-H bonds, these
carbohydrates are good for storing energy
• these bond types are the ones most often broken
by organisms to obtain energy
 the long chains are called polysaccharides
3.4 Carbohydrates
• Plants and animals store energy in
polysaccharide chains formed from glucose
 plants form starch
 animals form glycogen
• Some polysaccharides serve structural functions
and are resistant to digestion by enzymes
 cellulose is found in the cell walls of plants
 chitin is found in the exoskeletons of many
invertebrates and in the cell walls of fungi
Table 3.1 Carbohydrates and their functions
3.5 Lipids
• Lipids – fats and other molecules that are not
soluble in water
 lipids are nonpolar molecules
 lipids include fats, phospholipids, and many other
molecules
Figure 3.3(d) Polymers are built of monomers: lipid
3.5 Lipids
•
Fats are used for long-term energy storage

fats have two subunits
1. fatty acids
2. glycerol


fatty acids are chains of C and H atoms
Glycerol contains three carbons and forms the
backbone to which three fatty acids are attached
Animation: Energy Sources for
Prolonged Exercise
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3.5 Lipids
• Fatty acids have different chemical
properties due to the number of hydrogens
that are attached to chain of carbons
 if the maximum number of hydrogens are
attached, then the fat is said to be saturated
 if there are fewer than the maximum attached,
then the fat is said to be unsaturated
Figure 3.17 Saturated and
unsaturated fats
3.5 Lipids
• Biological membranes involve lipids
 phospholipids make up the two layers of the membrane
 cholesterol (a steroid) is embedded within the membrane
• Lipids also include oils, other steroids, rubber, waxes,
and pigments
Figure 3.16
Lipids are a key
component of
biological
membranes
Inquiry & Analysis
• Which of the three pH
values represents the
highest concentration
of hydrogen ions?
• How does pH affect
the release of oxygen
from hemoglobin?
How Does pH Affect a Protein’s Function?