Ch. 5 Structure and
Function of
Macromolecules
AP Biology
Macromolecules
• Most are polymers
• Polymer
– Large molecule consisting
of many identical or similar
building blocks linked by
bonds
• Monomer
– Subunits that serve as
building blocks for
polymers
Polyethene is a thermoplastic commodity heavily
used in consumer products (over 60 million tons are
produced worldwide every year).
A limitless variety of polymers can be
built from a small set of monomers
• Inherent differences between
siblings result from variations
in polymers
• Construction of
macromolecules
– 40-50 common monomers and
others that occur rarely
– Small molecules that are
common to all organisms are
ordered into unique
macromolecules
How Cells Use Organic
Compounds
• Biological organisms use the
same kinds of building blocks.
• All macromolecules (large,
complex molecules) have
specific functions in cells.
• Other than water,
macromolecules make up the
largest percent mass of a cell.
Condensation and Hydrolysis
• Condensation reactions
– Dehydration reactions
– When two molecules
become covalently
bonded to each other
through the loss of a small
molecule, usually water
• Hydrolysis
– Separation of two
molecules by the addition
of a water molecule
The Molecules of Life
• Large polymers form from smaller
monomers.
• New properties emerge.
• Living cells require/synthesize:
– Carbohydrates
– Lipids
– Proteins
– Nucleic Acids
Carbohydrates
• Used as fuel and building material
• Carbs are sugars and their polymers
• Main types:
– Monosaccharides
– Disaccharides
– Polysaccharides
Monosaccharides (CH2O)
• Generally have
molecular formulas in
some multiple of CH2O
• Glucose (C6H12O6) is
most common
• In aqueous solution
may form rings
• Major nutrients for cells
Disaccharides
• Two monosaccharides joined by glycosidic
linkages
• Glycosidic linkage
– A covalent bond formed between monosaccharides
• Sucrose is most prevalent
Dissacharide
Formation
Polysaccharides
• 100s to 1000s of
monosaccharides long
• Starch
– Storage poly. of plants
• Glycogen
– Storage poly. of animals
• Cellulose
– Structural poly. which is a major
component of tough plant cell walls
• Chitin
– Structural poly. used by arthropods
to build exoskeletons
Starch &
Cellulose
Forms ring in
aqueous
solution
Lipids
• Mostly hydrophobic
molecules with diverse
functions
• Little or no affinity for water
• Used for energy storage
and structure
• Main types:
– Fats
– Phospholipids
– Steroids
Fats
• Large molecules, but not
polymers
• Fatty acid
– A long carbon skeleton
with carboxyl group head
and a hydrocarbon tail
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Triacylglycerol (Triglyceride)
• Three fatty acids
linked to one
glycerol molecule
Saturated & Unsaturated
Fats
• Saturated fatty acids
– Fatty acid containing no
double bonds between
the carbon atoms
composing the tail
– Solids at room temp.
• Unsaturated fatty acids
– Has one or more double
bonded carbons in the
tail
Phospholipids
• Two fatty acid tails linked to one glycerol
molecule
– Ambivalent behavior toward water
– When in contact with water they form a micelle
(cluster)
Steroids
• Lipids characterized by
a carbon skeleton,
consisting of 4
interconnected rings
• Cholesterol
– Important steroid that is a
common component of
the membranes of animal
cells
– Many hormones are
steroids produced from
cholesterol
Proteins
• The molecular tools for most cellular
functions
• Used for:
–
–
–
–
Structural support
Storage
Transport of other substances
Signaling from one part of the organism to the
other
– Movement
– Defense against foreign substances
• Conformation
– Unique 3-D shape of a protein
Protein Polypeptides
• Polymers of amino
acids connected in a
specific sequence
• Amino acids
– Organic molecules
possessing both
carboxyl and amino
groups
• Acidity is determined
by side chains
Peptide Bonds
• Formed when an
enzyme joins amino
acids by means of
condensation
• Polypeptide
– Chains of amino acids
linked by peptide
bonds
Protein Conformation
• Conformation (shape) determines function
and is the result of the linear sequence of
amino acids in a polypeptide.
• Folding, coiling and the interactions of
multiple polypeptide chains create a
functional protein
• 4 levels of conformation
–
–
–
–
Primary
Secondary
Tertiary
Quartinary
Primary Structure
• Unique, linear
sequence of amino
acids in a protein
• A change in one a.a.
can effect every other
level of structure
– ex. point mutation in
hemoglobin
Secondary Structure
• Hydrogen bonding
occurs between amino
and carbonyl groups
of amino acids.
• Structures Formed:
• α Helix: Common in fibrous
proteins, creates “elastic”
properties.
• β Sheet: Anti-parallel
chains form sheet.
Tertiary Structure
• Irregular contortions from bonding
between side chains of various amino
acids
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Quartinary Structure
• Overall protein structure that results
from aggregation of tertiary subunits
Denaturation
• Unraveling and loss of native
conformation of a protein
• Can be due to heat, pH, salts, etc.
• Some can renature exactly, others
cannot
• Ex: cooking an egg
Nucleic Acids
• Store and transmit hereditary information
• Gene
– A unit of inheritance
• DNA & RNA
– Deoxyribonucleic acid & Ribonucleic acid
– DNA is like computer software, proteins are like
hardware
– Genetic info flows from DNA  RNA  protein
DNA Structure
• A polymer with an
information-rich sequence
of nucleotides
• Pyrimidine
– 6 membered ring made of
carbon and nitrogen atoms
– Cytosine and thymine
• Purine
– 6 membered ring fused to a
five membered ring
– Adenine and guanine
• Phosphodiester
– Covelent bonds holding
nucleotides together
DNA Structure, cont.
• Double helix
– Two chains of nucleotides
that spiral around an
imaginary axis
• Hydrogen bonds
– Hold two chains of
nucleotides together
• Adenine pairs with
thymine
• Cytosine pairs with
guanine
• Two strands of DNA
double helix are
complimentary
RNA
• Single stranded
• Four kinds of
nucleotide monomers
(A, U, C, G)
• Key players in the
protein-building
processes
• mRNA, tRNA, rRNA
DNA & Protein Importance
• Inheritance is based on precise
replication of DNA
• We can use DNA and proteins as “tape
measures” of evolution
– Linear sequences of nucleotides in DNA
molecules are passed from parents to
offspring
– More distantly related species have chains
that are less similar
Review questions
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Section 4.1 page 59, number 1
Read Inquiry 4.2. Think about the what if question.
Section 5.1 page 69, number 1
Section 5.2 page 74, number 3
Self quiz page 91 numbers 1-8.