Download Chapter 3 Presentation: Macromolecules

Chapter 3:
Chemistry of Life
Macromolecules
Macromolecules
• There are many molecules that comprise living
organisms and many of them are quite large.
• As such, they are called macromolecules.
• There are 4 main macromolecules that
comprise living organisms:
1. Proteins.
2. Lipids.
3. Carbohydrates.
4. Nucleic acids.
Macromolecules
• Three of the four classes (carbohydrates,
protein, and nucleic acids) are comprised of
polymers which are long molecules made
up of the same or similar subunits covalently
linked together.
• The subunits that are linked together are
called monomers.
Macromolecules
• The synthesis and breakdown of
macromolecules is governed by a series of
condensation/dehydration or hydrolysis
reactions.
Condensation Reactions
• In a condensation reaction (aka a
dehydration reaction) monomers are added
to a growing polymer and a water molecule
is given off--hence the name dehydration
reaction.
• These reactions require energy and the
action is carried out by enzymes.
Hydrolysis
• Hydrolysis is the process that adds a water
molecule to a polymer giving one of the
monomers.
• This occurs during digestion and it makes the
large molecules useable by our bodies by
producing smaller subunits that our cells can
uptake.
• The four main types of macromolecules can be
broken down further and analyzed.
Carbohydrates
• Carbohydrates are molecules consisting
of carbon, hydrogen, and oxygen.
• The three classifications are
monosaccharides or simple sugars,
disaccharides or double sugars, and
polysaccharides which are 3 or more
sugars linked together forming a sugar
polymer.
• They are involved in storage functions,
structural functions, and cell recognition
functions.
Monosaccharides
• Monosaccharides generally have the
formula CnH2nOn.
• C6H12O6, for example.
Disaccharides
• A disaccharide, such as sucrose and
lactose are joined together by a
glycosidic linkage--a covalent bond
between 2 monosaccharides by a
dehydration reactions.
Disaccharides
• The fruit of a plant is often a great source of
sucrose (the most common disaccharide)
consists of glucose and fructose.
• It’s the most common because as the plants
form it during photosynthesis, this is where it
gets stored.
Polysaccharides
• When monosaccharides are glycosidically
linked together thousands of times,
polysaccharides are formed.
• There are 3 main types of polysaccharides,
structural, storage, and those involved in cell
to cell recognition.
Structural or Storage?
• There are actually 2 forms of glucose, α and
β, and the form is determined by the
placement of a hydroxyl group.
Structural or Storage?
• In α-glucose, the -OH group is below the
ring structure and in β-glucose, it is above
the ring structure.
Structural Polysaccharides
• In structural
polysaccharides,
strong materials are
built to provide
strength and support
for the organism.
• A good example of
this is cellulose.
Structural Polysaccharides
• Plant cell walls are comprised of cellulose
which gives them strength. Some animals
such as cows can digest cellulose, but
humans can’t.
• For us, it is called “insoluble fiber” and is
found in many fruits and vegetables.
Storage Polysaccharides
• Although the starch and cellulose molecules
are comprised of glucose molecules, the
different types of glucose give them vastly
different uses.
• For example starch can be used by humans
for food, cellulose can’t.
Storage Polysaccharides
• There are two main
types of storage
polysaccharides:
That which is found
in plants (starch),
and that which is
found in animals
(glycogen).
• Glycogen is
branched, and
starch is helical.
Proteins
• Proteins are another
class of
macromolecules
consisting of many
monomers linked
together by peptide
bonds forming polymers.
• Enzymes are protein
polymers that act as
catalysts within cells.
Proteins
• Polymers of amino acids are called
polypeptides and the same 20 amino
acids form all polypeptides.
• Proteins consist of one or more of the
polypeptides coiled into a specific
conformation.
Proteins
• Amino acids are
organic molecules
containing a
carboxyl group and
an amino group.
• These are each
bounded to a
central carbon atom
which also has an
amino acid
attached to it.
 carbon
Amino
Group
Carboxyl
Group
Proteins
• There are 2 groups that are linked together
to form a peptide bond.
• A peptide bond is a dehydration reaction
which links the amino group of one amino
acid to the carboxyl group of a different
amino acid yielding water in the process.
Proteins
• Once amino acids are added to the
polypeptide, they begin to interact with the
other amino acids on the growing
polypeptide.
• The sequence then determines the 3D
conformation the protein will take.
• The conformation of the protein determines
how it will function.
Proteins
• An enzyme is an example and the
conformation it takes determines how it
functions when it interacts with a substrate.
• There are 4 different types of protein
structure: 1°, 2°, 3°, and 4°.
Proteins--Primary Structure
• The primary structure is
the specific sequence
of amino acids.
Proteins--Secondary Structure
• The secondary structure of the polypeptide is
the coiled and/or folded patterns that emerges
as the amino acids begin to interact with one
another (H-bonds) not from the R-groups, but
from the backbones of the amino acids.
Proteins--Secondary Structure
• There are two main types of secondary
protein structure, the α-helix and the βpleated sheet.
• The α-helix is a delicate coil held together
by H-bonds.
• The β-pleated sheet forms when 2
polypeptides are aligned side by side and
hydrogen bond along their lengths.
Proteins--Tertiary Structure
• The tertiary structure
of the protein is due
to the interactions of
the R-groups on the
amino acids.
Proteins--Quaternary Structure
• The quaternary structure of a protein
occurs when 2 or more polypeptide
chains interact with each other to form a
large, functional protein.
Nucleic Acids
• Nucleic acids store and transmit information
about a protein’s primary structure.
• There are 2 types of nucleic acids: RNA and DNA.
• DNA provides the necessary information for
guiding its own replication.
• It also guides RNA synthesis and using RNA
controls protein synthesis.
Nucleic Acids
• DNA is the information that controls the cell.
This information is used to create messenger
RNA that interacts with the cells protein
synthesizing machinery (ribosomes) to
create the proteins that run the cell.
• DNA--> RNA --> Protein
Lipids
• There are three classes of lipids:
• Fats (Fatty acids)
• Phospholipids
• Steroids
• Waxes
Lipids
• Lipids are not polymers, they are long chain
fatty acids attached via a dehydration
reaction to a glycerol head.
Lipids
• The fatty acid portion is a long hydrocarbon
usually 16 to 18 carbons in length.
• These portions are hydrophobic and this
makes fats hydrophobic.
• Fatty acids can be classified as saturated or
unsaturated as we often hear about in
nutrition.