Four
major groups of macromolecules are essential for the life of the cell:
carbohydrates, lipids, proteins and nucleic acids. These four
categories
of molecules consist of very large organic compounds with an enormous
variety
in terms of function. Fortunately, the basic concept of their structure
is a simple one: a large number of building blocks (monomers) are
joined
together with covalent bonds to form larger molecules (polymers). Their
unique structures give them a variety of different functions within
living
systems. Natural selection and the process of evolution is the source
of
variety in structure and function in these molecules.
Review
Questions: [continue
to the links
or the outline]
It is often stated
that
life is
made of organic compounds. What exactly is meant by that statement?
The carbon atoms and
other elements
are joined to form different functional groups. How does different
functional
groups affect the different properties (charged, non-charged, bulky,
small,
polar, non-polar etc.) of a molecule?
How do monomers form
polymers
via dehydration synthesis?
How are polymers
broken
down to
monomers via hydrolysis?
Note: You need to
be
able to
recognize different types of monomers and polymers. E.g. assume the
test
has a figure of fructose. You should be able to recognize it as a type
of monosaccharide
(simple sugar). A figure of any of the twenty amino acids should be
recognized
as an amino acid and so on.
What is a
monosaccharide? Give
examples of, and recognize figures of, monosaccharides
(simple sugars).
What is a
disaccharide?
Examples?
Understand the
concept
of polysaccharides.
Describe the following three examples of polysaccharides (including
their
source and function): Starch, glycogen
and cellulose.
What is a lipid
(definition)?
How do hydrophobic
and
hydrophilic
compounds differ from each other?
What is the function
of
fats and
oils in living organisms?
Do animals use fats
differently? E.g.
compare a seal, a marmot and a fox in terms of how they use their
adipose (fat) tissues.
Animals often use fat
as a way to store
energy. Why do animals not typically store energy in the form of
carbohydrates?
Fats are often
referred
to as
triglycerides. Describe the basic components of a triglyceride.
What is the
difference
between
unsaturated and saturated fatty acids?
Can you give
examples of
where
one can expect to find unsaturated and saturated fats? Is there a
reason
for why either of these fats/oils dominate in those organisms?
There are other
types of
lipids
than triglycerides. Some examples are phospholipids, waxes and
steroids.
Briefly describe how these differ from each other as well as their
function
in biological systems.
Give examples of
different kinds of
steroids.
What is an anabolic
steroid?
Proteins are very
important macromolecules.
Give six examples of the different functions proteins can have within
an
organism.
Are proteins
important? Why?
What are the
building
blocks for
proteins? How many different kinds of these building blocks are
available
for human proteins?
Sketch an amino
acid.
Would you
recognize it on a test?
How are amino acids
joined together
to form a peptide?
What is the
connection
between
the shape of a protein and its function?
What is
denaturation?
What causes
denaturation? How does the process of denaturation affect the function
of a protein?
Define the primary
structure of
a protein.
Define the secondary
structure
of a protein (local folding into a helix or a sheet).
Define the tertiary
structure
of a protein. It is crucial that you understand how the shape of a
protein
determines its function.
Define the
quaternary
structure
of a protein (more than one polypeptide unite to form the protein e.g.
hemoglobin). Do all proteins have a quaternary structure?
Who is Linus
Pauling?
How did
he contribute to our knowledge of macromolecules?
What is the role of
nucleic acids
in living organisms?
There are two
different
types
of nucleic acids in a cell. What are they and how do they differ from
each
other in structure and function?
What is adenosine
triphosphate
(ATP)?
What is the function
of
DNA?
What
are
the building blocks of nucleic acids?
Describe how the
building blocks
(nucleotides) are joined together with covalent bonds to form a
macromolecule
(nucleic acids).
Know the general
structure of
the double helix and the concept of base pairing (A with T, G with C).
What is the
complementary sequence
to the following DNA sequence: ATC CTA AAC GTA?
Lecture Outline Macromolecules: We
will look at four major groups of macromolecules: carbohydrates/
lipids/
proteins and nucleic acids. These very large molecules fulfill
important
roles in the cellular realm.
The building blocks of
macromolecules
are referred to as monomers. The macromolecule itself is a polymer.
The process by which the
monomers
are joined together to form the polymer is called a condensation
reaction.
The breakdown of the polymer
to form the monomers is called hydrolysis.
Carbohydrates
"Carbon water" -
since
they are formed by the elements C, H and O. If these atoms are counted
in a sugar molecule they will form a multiple of C and H2O. All the
molecules
in this group (from the small sugar molecules to the enormous starch
molecules
(macromolecule)) are referred to as carbohydrates.
The building blocks of
carbohydrates
are referred to as monosaccharides (or simple sugars). Examples of such
sugars are glucose, fructose and galactose.
Disaccharides are
two monosaccharides
joined together (e.g. sucrose, lactose or maltose)
Monosaccharides and
disaccharides
are joined
together to form polysaccharides.
Polysaccharides: large
polymers
of simple sugars connected with covalent bonds Examples:
starch
(storage of
energy in
plants)
glycogen
(storage
of energy in
animals [liver, muscle] (remember that most of the energy in animals is
stored in the form of fat [triglycerides]); branched structure for
faster
access)
cellulose
(structural carbohydrates
in plants and algae in their cell walls) [all of the three
carbohydrates
above are made of glucose units as monomers]
chitin
(structural
component of
fungi (cell walls) and in exoskeletons of arthropods [e.g. insects and
crustaceans]
starch
(energy storage
in plants)
glycogen
(energy
storage in animals esp in muscle tissue and the liver)
cellulose
(structural component
in plants (cell walls))
Lipids
A group of several types of
molecules. They are all referred to as lipids since they cannot be
dissolved
in water. They are hydrophobic ("water fearing").
In contrast a hydrophilic
("water loving") compound is attracted to water.
Understand the difference
between hydrophobic versus hydrophilic characteristics in a molecule.
We are studying A. Fats, B.
Phospholipids and C. Steroids in this section.
A.
Triglycerides
or Fats/oils (components:
glycerol + three fatty acids)
There are
two
major types of fatty acids: unsaturated versus saturated fatty acids;
these
are the building blocks of fats.
The
presence
of double bonds in an otherwise uniforms chain of carbon and hydrogen
atoms
cause kinks in the molecular structure.
Unsaturated
fatty acids are prominent in triglycerides with an origin from
plants.
FATS: (glycerol
+ three
fatty acids) [triglycerides] (to the right)
Biological roles:
energy storage
(2x energy/weight
compared to carbohydrates). It is not surprising that animals were
selected
for using fat for energy storage since it is an efficient form of
storing
energy relative to its weight. Plants tend to use starch instead for
storing
energy. Why do you think that is?
insulation:
especially prominent
in some mammals and birds. Recall the example from class (penguins and
seals).
padding (some
organs have extra
padding of fat)
The diagram to the
right compares
a saturated versus an unsaturated fat molecule. Notice the "bulky"
aspect
of the unsaturated fat. What do you think are some possible
consequences
of this "bulkiness"? In which organisms do you tend to find unsaturated
fats? Why do you think that is?
B. Phospholipids
(glycerol + two fatty acids + phosphate group [polar])
the
molecules
form a bilayer in water. One part of the molecule is hydrophobic while
the other is hydrophilic (this is often referred to as amphipathic).
Phospholipids
is
a basic structural component of the cell membrane. You will learn more
about membranes later. They serve as selective barriers.
C. Steroids
Some hormones
are
steroids (estrogen/ testosterone)
Another example
is cholesterol is an important structural componment of cell membranes
in animals (it stabilizes the fluidity of the membrane).
Proteins:
Crucial
functions in
the organism
Examples:
structural
proteins (e.g. keratin
in hair, nails and skin)
enzymes (e.g.
amylase that breaks
down starch to maltose)
antibodies
(immunoglobulins [Ig])
hormones (not
all)
(e.g. insulin
and human growth hormone)
clotting
factors
in blood
transport
proteins
(e.g. hemoglobin
transporting oxygen)
membrane
proteins
Amino
acids are the building blocks of proteins.
The
figure above shows the basic structure of an amino acid
(R is the variable
side chain
that strongly influences the property of
the amino acids (see
below))
There are 20 different
kinds
of amino acids in the human species
(you do
not need to
memorize them!).
Each amino acid has different chemical properties
(large vs small,
hydrophobic
vs hydrophilic)
The amino acids
are
joined by peptide bonds (a type of covalent bond) to form a polypeptide.
The amino acid sequence will
determine the three-dimensional structure of the protein which
ultimately
is linked to its function. Since life is waterbased their behavior
relative
to water is very important. The protein folds into a unique structure
as
it is exposed to a water environment.
The structure of
proteins
can be viewed as primary, secondary, tertiary and quaternary structure
The three dimensional
shape
of the protein very important for its function.
This shape is
influenced
by the solvent (water) as well as surrounding solutes, pH and
temperature.
Even physical pressure can affect the shape. This is not something that
is critical for us as humans, but for deep sea fish species it is a
critical issue.
Denaturation of proteins
(caused
by temperature or chemicals) may inactivate the protein (this may be
irreversible)
by changing its tertiary structure.
Nucleic acids
function:
information
carriers and information storage
deoxyribonucleic acid
(DNA)
ribonucleic
acid (RNA)
building block:
nucleotides
(a 5-carbon sugar + a phosphate + a nitrogenous base)
4 bases in DNA:
adenine,
thymine, guanine, cytosine (A T G and C)
4 bases in RNA:
adenine,
uracil, guanine, cytosine (A U G and C)
link the
nucleotides
to form a polynucleotide (a nucleic acid)
DNA: double helix
made of
two chains of polynucleotides
Watson and
Crick determined
the structure of DNA in 1953
the bases face
inwards
and pair up ( A with T / G with C)
the pairing is
a weak
interaction: hydrogen bonds
the pairing
gave Watson
and Crick the firs clues in regards to how the DNA double
helix replicates.
After
reading these chapters you will have the fundamental knowledge to
approach
biology on a cellular level. Remember to not be intimidated by complex
terminology. You
are learning a lot of new concepts
and structures. It is necessary to use labels to be able to study the
cellular
realm and journey further into the field of biology.
Biology
Book - Water/ Organic Molecules
: An
excellent
overview of water chemistry as well as of the macromolecules with lots
of graphics. The page may take a while to load unless you have a fast
connection,
but it is definitely worth the wait.
Page
created by: Peter
Svensson Updated:
February 17, 2010
