This is going to go over
An Introduction to Metabolism and Enzymes.
Metabolism is what keeps cells running.
This is the topic for this section of the course.
Metabolism involves both
building and breakdown reactions.
All of this is fundamentally linked 
to the cell's energy supply
mainly in the form of the ATP molecule.
When energy is supplied, ATP is utilized,
and a phosphate is released forming ADP
and a P.
The energy producing reactions 
recouple ADP to P to form ATP.
This cycling continues 
as long as metabolic processes occur.
The definition of metabolism is:
the sum of all the chemical reactions in a cell.
The ultimate goal, of course, is for
reproduction of the cell and or organism.
Catabolic pathways are the ones
that break up larger molecules into smaller products
They release energy.
The chemical term is exergonic.
These reactions release energy.
This is referred to as spontaneous,
but it does not equate to fast.
Think of how long it might take 
for a car to rust in your driveway.
That's spontaneous but not quick.
Anacboli-- Anabolic pathways 
synthesize or make things.
They are also required and in--
they also require an input of energy.
The term is endergonic.
They are also not spontaneous.
Oxidation-Reduction Reactions 
are essential to the system.
The chemical slang, or the shortened version, is Redox.
In a Redox Reaction,
there are partner molecules.
One gives; one takes.
The donating molecule gives up an electron,
and sometimes a hydrogen.
The receiving molecule picks these up.
Cells have specific molecules designated
to carry the electrons and hydrogens.
The three most important 
electron carriers in the cell,
to be discussed in this chapter,
are NAD+, NADP+ and FAD.
You may wonder what exactly these are.
They're just molecules,
modifications of nucleotides.
You don't need to remember 
the chemical name, just the abbreviation.
This image is illustration 
of a REDOX Reaction.
The electron donor molecule passes 
the electron to an acceptor molecule.
The donor is said to be oxidized in the process.
The receiver is reduced.
If you remember the mnemonic OIL-RIG,
for Oxidation Is Loss
Reduction Is Gain,
it helps clarify the terms.
The loss is of electrons, and
and usually hydrogens, and same for the gain.
As mentioned earlier the purpose of 
many of the catabolic reactions is
to produce ATP for use to 
power the anabolic reactions.
All this attention on ATP,
we need some terms.
Phosphorylation is the chemical term for
adding a phosphate group to a molecule.
Remember a phosphate group
from the functional group section?
Phosphorylating ADP is what the cell does
to produce the necessary stores of ATP.
Cells phosphorylate ADP to ATP,
in three ways.
One is substrate-level phosphorylation.
Two is oxidative phosphorylation.
And three is photophosphorylation.
We'll discuss each of these 
at various points in this chapter.
the whole purpose of producing atp is
power the anabolic reactions
that use the stored energy by removing
the phosphate from atp to produce atp
this image is illustrating the key
players in metabolism the enzymes
an enzyme will bind a specific molecule
termed
a substrate in the active site
when it does bind the enzyme shifts
shape to clamp down on the substrate
to enable a reaction to occur see this
yellow substrate
it fits in the blue enzyme depicted on
this right and notice how the enzyme
shifts its shape to better enclose
that substrate this is going to promote
the chemical reaction in the substrate
be that a splitting or a joining type of
activity
that depends on the substrate or
substrates and a given enzyme
enzymes are and enzymes are
catalysts of chemical reactions in the
cell
catalysts are unchanged themselves but
they promote a chemical reaction
thus one enzyme can perform many many
chemical reactions with the substrate
enzymes are largely composed of protein
the protein component is an apo enzyme
cofactors such as ions or coenzymes
like vitamins are often needed for an
enzyme to function
when all of the necessary components are
present
this is termed a holoenzyme
consider your bottle of supplements in
your home something like
flintstones or in my case centrum silver
the side of the bottle will list the
nutrients like calcium magnesium
zinc in addition to vitamin d
c e etc what are these
simply put they are the cofactors and
the coenzymes needed to keep your
enzymes functional
of note rna can have a catalytic
activity as well
these special rna molecules are termed
ribozymes
as mentioned catalysts are responsible
for driving the chemical reactions in a
cell
this graphic is depicting a set of
reactants that inherently possess
a certain level of energy within it
after the reaction depicted here
the products contain less energy
the line forming the upper dome
represents the amount of
activation energy needed to get the
reaction going
if no enzyme is present activation
energy is the energy needed to get a
reaction going
imagine a rock sitting on the end of a
cliff if you kick it
that that's the activation energy it
will fall off the cliff and
dive toward the earth below you notice a
dotted red line under that larger dome
this represents the amount of activation
energy if there
is an enzyme present it's less
and this is why enzymes speed up a
chemical reaction
by the way this is a spontaneous
reaction
that is depicted because the products
have less energy than the reactants so
energy came out
enzymes are proteins and proteins rely
on their shape
to perform their function you can alter
the environment only
so much before you affect the folding of
the protein and thus its function
the first graphic depends depicts a
rising temperature
on the x-axis and the activity of the
enzyme
on the y-axis
as you as you can see there is a point
of optimal activity
as you cool or you heat up the
environment
you reduce the enzyme function
ph demonstrates a similar effect to
acid or too basic
you reduce the enzyme functioning
this last graphic has a different shape
it's demonstrating the effect of
substrate concentration on activity
you can increase the substrate comp
concentration
only so much at some point you have
maxed out the system and the enzyme
cannot produce more products
any faster despite an increase in
substrate
the activity hits a plateau
this image is demonstrating a particular
protein in a normal conformation
and on the right the same protein has
loosened up
and unfolded this state is termed
denatured
denatured proteins aren't functional and
often they can't refold properly once
they are denatured
even if returned to a
optimal condition
chemicals other than the substrate can
bind an enzyme and interfere with enzyme
function
in this image the pink square molecule
represents a competitive inhibitor
such an inhibitor can bind the active
site of an enzyme
and block the substrate
the substrate is represented by the
clover-like molecule
in this image competitive inhibitors can
be overcome by
flooding the system with extra substrate
in this way you minimize the chance
that an inhibitor molecule has the
ability to bind
the active site of the enzyme
this image depicts a non-competitive
inhibition
a non-competitive inhibitor binds the
enzyme
in a spot other than the active site
this other site is designated an
allosteric
site an allosteric inhibitor is another
way to describe
a non-competitive inhibitor as you can
see in the image
the allosteric inhibitor binds and
causes a conformational
change in the enzyme such that the
substrate can no longer bind to the
active site
non-competitive inhibitors cannot be
overcome
by flooding the system with substrate
only when the inhibitor is removed
will the enzyme function again
the last concept of this section
is feedback inhibition this is the name
for a very common phenomena in cells
in this process the final
product of an enzymatic
set of reactions acts as an allosteric
inhibitor to the first enzyme in a
process
note that on this image to the left
there is a series of enzymatic steps
that work on the product of a previous
reaction
using the product to be the substrate
that produces another product
the last product in such a pathway is
termed the
end product the end product is an
allosteric inhibitor of the first enzyme
then
shutting down its own system
this is key to regulating substances in
the cell if a cell has plenty of an end
product it will halt the synthesis
pathway until it's needed again
that's pretty nifty don't you think this
particular
image from your book is just showing
some of the different feedback
inhibition systems that are known
in metabolism these are systems that
produce
amino acids such as tyrosine
phenylalanine
and tryptophan well this includes the
introductory section of the metabolism
module
