ENZYMES
NATURE’S EFFICIENCY EXPERTS
WHAT ARE ENZYMES?
• Enzymes are a special group of PROTEINS
Remember proteins are responsible
for structure and function
• They are referred to as CHEMICAL CATALYSTS
because they control chemical reactions without
becoming a part of them.
• The enzyme itself is not changed in the REACTION and
CELL PHONE
can be used
again and again.
EXAMPLES OF ENZYMES
• Most enzymes names end with –ase.
• Usually they are named for
the material they are acting
upon…
• Lactose is digested by lactase
• Sucrose is digested by sucrase
• Cellulose is digested by cellulase
and so on…
• What exactly does “digestion”
mean? To break bonds
between monomers in a large
polymer through enzyme activity!
NOT THIS…AGAIN!
HYDROLYSIS = DIGESTION
BREAKING DOWN
CONDENSATION = SYNTHESIS
BUILDING
BOTH REQUIRE ENZYMES!
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ENZYME CONTROL: DIGESTION
• There are over 4000 biochemical reactions that
are controlled by enzymes…
• Digestion: Amylase digests
carbohydrates into
monosaccharides.
• Amylase is in saliva.
• There are 7 digestive
enzymes.
ENZYME CONTROL: TOXIC BY-PRODUCTS
• Toxic By-products: Biochemical reactions
often produce substances that can be toxic
to cells. Enzymes digest them into substances
that are not harmful.
The enzyme catalase digests
hydrogen peroxide(H2O2)
into H2O and O2.
BTW: Not a good idea to use peroxide
on boo boo’s. The enzyme reaction
kills bacteria, but, it also kills healthy
cells too which means healing slows!
ENZYME CONTROL: POISONS/PRODUCTS
• Poisons: Act as enzyme inhibitors; they
prevent enzymes from working.
Examples like Raid(animals) and
Round-Up(plants). They kill certain kinds
of organisms without harming others
because they act on enzymes that are
specific to them. Many animal toxins
like snake venom do the same thing.
• Products
‘Biological’ stain or spill cleaners
Meat tenderizers(think about it!)
HOW ENZYMES WORK
• Enzymes are chemically and structurally
matched to the biomolecule
they digest(or build)…
In much the same way that
a key fits a lock, in fact this
“lock and key” analogy
is often used to describe
enzyme activity.
Let’s see why…
“LOCK AND KEY” MODEL
Sucrose
Glucose
Lock and Key
Sucrase
Enzyme changes
Shape and by heat
and friction the
bond is broken
Fructose
Once bond is broken
products are released
enzyme continues to
work as long as
substrate is present
It is important to note that this reaction can run in the opposite
direction…to build polymers. However, a different enzyme is
used and are called polymerases.
WHY ARE ENZYMES SO IMPORTANT?
• Because Nature Loves Efficiency!
• In order for all of the activities of life to occur; all the
chemical reactions, building and breaking down of
macromolecules, repair and maintenance of structures…If
cells had to wait around for these materials and reactions to
occur spontaneously…life would not be possible!
• Also, needless to say all of those activities require a great
deal of energy to get started, or keep going, or stop!…so
much so that those little mitochondria would not be able to
produce enough ATP fast enough to fuel everything a cell
has to do…again life would not be possible!
• Enzymes get the job done without the cell having to
expend the energy to do it! In other words they
lower the activation energy of chemical reactions
so they go faster and result in more product!!!!
COLOR PIECES USING ANY 3 COLORS
DO NOT COLOR THE ENZYME
HOW CAN WE VISUALIZE AN
ENZYME REACTION?
• NO Enzyme:
•
• High activation
energy
• Longer time
• Less Product
• With Enzyme:
• Less activation
energy
• Less Time
• More Product
MORE EFFICIENT!
CONCENTRATION OF SUBSTRATE
So…What happens if I eat this huge pizza?
You might think a lot more enzyme will be
produced to take care of this “extra large”
digestion issue…and you’d be right, to a
point…
Enzyme-substrate reaction rate depends
upon open activation sites; enzyme
production takes time…so, once all
available enzymes are in use, digestion
can actually slow and reach a plateau.
So, eating a lot-all at once-can actually
slow digestion down…mom is right, slow
down and chew your food smaller pieces
means enzymes can digest their substrates
faster!
ENZYMES CAN BE ALTERED …
• Enzymes are very sensitive to their
environment
• Any change can result in an enzyme that
will not work effectively, or, not at all…at
that point the enzyme is said to be
denatured.
TEMPERATURE
Any increase or decrease in the
temperature at which the enzyme
functions changes the shape of the
activation site. Just like when heating
wax causes it to fold and bend.
If the activation site changes shape
then the “key” no longer fits the “lock”
and the reaction stops.
This is why food doesn’t ‘digest’ well
when you have a high fever, and
…..well, you better be real close to a
toilet!
pH CHANGES
Any increase or decrease in pH can
denature an enzyme. pH is the measure
of how acidic or basic a substance is
Intestinal enzymes work best in neutralbasic environments
Stomach enzymes, like pepsin, are
designed to work best at a low pH(high
acid)
When you have an invasion of nasty
food borne bacteria, their metabolism
neutralizes your stomach pH, your
enzymes denature, and, again…
where’s that toilet!
GENETIC MUTATION
Since enzymes are proteins; their manufacture
depends upon a correct amino acid
sequence, and since that is determined by
DNA, mutation can change the “nature” of a
protein.
Lactose intolerance is caused by a mutation.
Folks with this mutation produce ineffective
lactase, i.e. the shape of the “lock” is changed
because the amino acids are incorrect; as a
result they cannot properly digest milk sugar.
If they eat dairy, the sugar is fermented by
intestinal bacteria doing their anaerobic thing
and, oh gosh…
Where’s that toilet again!
Lactase
in a box!