Now we can begin talking about the four major classes and macromolecules
found in biological systems and they are carbohydrates,
nucleic acids, the proteins
and lipids or fats, lets call them
lipids actually because fats are a subclass of lipids so we have carbohydrates, nucleic
acids,
proteins and lipids. We can
talk about how these polymers are build up,
what subunits are involved, that is
what monomers are involved
in being linked together to form these
various macromolecules
that are the carbohydrates, nucleic acid,
proteins or lipids
so for carbohydrates if we look at the
types of carbohydrates that are
common there are others but let's just
look at these we are starch and
glycogen which
are the storage forms of carbohydrate
in animals and plants, plants for starch,
glycogen in animals
and the subunit is a sugar molecule
called glucose that we'll
looking at and glucose is polymerized into starch or glycogen
and then when glucose is needed.
Starch or glycogen is broken down
into glucose which can then be fed
into the metabolic pathways to generate
the energy currency of the cell ATP
will talk about that later. So glucose, starch and clycogen for energy
storage
an example potatoes, potatoes are full of starch. Beets are
another example the roots of major plants are storage organs basically for
starch which can be used for energy later
cellulose is also a polymer of glucose.
Glucose being the monomer and celluloseis
one of the most abundant macromolecules on earth, if not the most
and it forms the cell walls, a major component
of plant cell walls. Paper
strings of celery the cellulose you find in celery, the reason you find it so fibrous
is because of cellulose we'll
talk more about that as well
now chitin is a modified glucose
molecule that is polymerized to form
chitin a type of carbohydrate that is
instructed, that is used for structural
support for the exoskeletons
of invertebrates of insects
and crabs and lobsters and things
like that so chitin
is an important
structural support it's also chitin is
also
found in fungi; mushrooms
interestingly enough so both
invertebrates
and fungi have seized upon chitin
as there skeleton support for them
its again its a polymer of modified glucose
now the nucleic acids named because they are acidic due to phosphate groups that we'll
talk about
and they found in the nucleus of cells
the nucleic acids
DNA and RNA and the building blocks for
DNA and RNA are nucleotides
that are polymerized to form RNA or DNA depending on the nucleotides that are
being used
DNA is the stuff of genes
and those genes carry the instructions
to build organisms and run the
biochemistry of
the cell an RNA as we will see and study
is needed for gene expression. Examples
DNA is found in chromosomes and
RNA a type of RNA called messenger RNA is used as the
messenger that links the
gene to proteins and we'll talk about the coding and decoding
of genetic information we will see that
messenger RNA is very important. Now
proteins
we can have functional proteins or structural proteins they're both
polymers of amino acids that are linked
together
for functional proteins there are many
things that proteins can be involved in
they can the enzymes that promote
biochemical catalysis and run the
biochemical pathways in the cell they can be used
proteins can be used for transport,
protein can be used as defense mechanisms the
immune globulin proteins that are an
important part of our
immune systems, our response to the
invasion of our bodies by foreign substances those
immune globulins are proteins they are proteins
that our regulatory proteins that bind
to DNA and
term genes on or off, there are
storage proteins, proteins can be used to
store
energy although usually
lipids or carbohydrates are used for that function and proteins can also
be used in transport as we will see proteins form molecular motors that
move substances within cells
and proteins are also conform rigid
support
in structures of the cell
these cytoskeleton that we will talk about. So examples for structural
proteins hair
silk the actin
microfilaments that we'll find in
cells that are part of the cytoskeleton
an example the functional protein would be hemoglobin which
carries
oxygen around in our blood streams. Now lipids the fourth major class of
macromolecules
we have fats, phospholipids,
prostaglandins, steroids, terpeines as examples of the lipids there
fats are used for energy storage and the
subunits the monomers that
are linked together to form fats are glycerol
and 3 fatty acids that are linked together
with the glycerol
we'll talk more about that shortly. Examples butter, corn oil, soap
fossil lipids are used in membranes
they are the major component of biological
membranes
the plasma membrane of cells as well as
the subside compartments in your
eukaryotic cells that we will mention
fossil lipids are made of glycerol as our fats
but linked to that glycerol are two fatty acids not three
and a phosphate and another polar group
atoms linked together, the polar group, the polar functional group
those constitute phospholipids then
we'll talk a lot about those we'll spend
a lot of time talking about membranes
and the importance of membranes for
cellular life
now prostaglandins are
are chemical messengers like prostaglandin E, for example
and prostaglandins are five carbon rings with nonpolar hydrophobic tails
on them. Very important signaling
molecules
steroids also are used as signaling
molecules they are hormones like
estrogen and testosterone these primery sex hormones
but they also, steroids can also
be components membranes they can fit
into the phosolipids bilayers that
constitute
membranes as we will see
and steroids then are there four fused carbon rings
join together those identifie the steroids
and finally terpeines are a type to lipid
that are very long
carbon chains and they are,
they function as pigments or structural support
especially in plants and examples are
carotene,
that
causes carrots to be
orange carotene is a pigment and
carotene is also
a precursor to you some vitamins used in
animals
that animals need and rubber natural rubber. Now we all have synthetic rubber but
in the old days
rubber was all natural derived from rubber   trees and rubber
is basically an example
of polymer long carbon chains polymerized into terpeines
so now we're going to consider two types of
key biochemical reactions that
are used to polymerize monomers into
polymers
and then the reaction that depolymerizes 
polymers into individual
building blocks or monomers so first
dehydration synthesis
is used to polymerize many
polymers that we find
so for example here are
two molecules that are being linked together
and this carbon is being joined to that
carbon
and what's being removed is one hydrogen, two hydrogens and an oxygen
which form molecular water so
dehydration reaction that is we're removing water
we're dehydrating. it's also known as
condensation reaction just like you know
if you have water condense, if you breathe out onto a
cold surface your breathe will condense onto that surface
that's water condensing on the surface so dehydration reactions or condensation
reactions
remove water and are used often to
polymerize
sub-units into you polymers whereas,
hydrolysis this that is the addition of
water hydro meaning water
-lysis meaning to break up water can be added
to break up a polymer into individual
building blocks into individual monomers so
hydrolysis is the opposite of condensation or dehydration reactions
and these are very important in the
polymerization of
macromolecules in the depolymerization of macromolecules
water is heavily involved now.
So you'll want to get that straight dehydration is
used in synthesis hydrolysis is used in
breaking down
so now lets move on to talking specifically about carbohydrates
we'll now treat all four classes individually: carbohydrates,
nucleic acids, proteins and lipids
and we'll speak about those in each
in a bit of detail let's start with
carbohydates. So carbohydrates
are characterized by having a particular ratio of carbon, hydrogen, oxygen
that's what constitutes a carbohydrate
namely
one carbon to two hydrogens to one oxygen
so you could just say that this is
CH2O
times how many ever
how many ever repeats of this particular empirical formula there is
so one to two to one ratio of carbon hydrogen oxygen
and as you can see then there's
a lot of carbon and hydrogen
present a lot of CH bonds and those
those carbon hydrogen bonds are,
are high energy bonds they can be broken to derive energy from them
that's why carbohydrates are good storage molecules
for energy. So
as I have said the CH bonds hold a lot
of energy and therefore
carbohydrates are good energy storage molecules like sugars. sugars are
carbohydrates, starch
is a storage form of sugar linked together
glucose is a single sugar
so we'll come across these again. let's talk about some of these
carbohydrates
lets look at some monosaccharides mono meaning one and saccharides meaning sugars
so lets look at single ring sugar 6 carbon sugar
like glucose. six carbons twice that
number of hydrogens
and six oxygens one to two to one ratio
and fructose, fruit sugar, sugar found primarily in fruit
is an isomer of glucose is the structural isomer of glucose as we will see
whereas galatose is a stereoisomer we've already talked about that actually
we will revisit it briefly
now the enzymes that
are present the protein enzymes that,
that breakdown sugars or
that link sugars together into starches
can recognize the different isomers that
of the six carbon skeleton so this is
where isomers a very important
some of them are recognized by one enzyme other
isomers are recognized by other enzymes
now in starting the next section we'll talk about
these different isomers of a molecule glucose
talk about isomers of monosaccharides glucose
and look at the difference between
those isomers
and then that will set up later talking
about how those different
isomers of glucose are utilized to
form different starches
