In This Lesson:
Enzymes and
Reactions
(Lesson 9 of 9)
Today is Friday (!),
October 2nd, 2015
Pre-Class
In your notebook, write
down your definition of
what energy is. What does
energy do? Better yet,
where is the energy in this
picture?
P.S. There’s homework, but it’s short.
P.P.S. Turn in your homework if you did it
on paper.
http://todaysfacilitymanager.com/facilityblog/wp-content/uploads/energy_plant_21.jpg
Pre-Class #2
• What is your ideal temperature for the
thermostat?
– I’m going to ask all of you.
http://www.library.drexel.edu/blogs/thesuggestionbox/Thermostat.jpg
Today’s Agenda
•
•
•
•
•
Review
Energy
Chemical Reactions
Enzymes
Enzyme Contest
• Where is this in my book?
– P. 43-44, 76-77
By the end of this lesson…
• You should be able to identify the properties
of enzymes and the function of the active site.
• You should be able to describe how enzymes
catalyze chemical reactions and make life
possible.
Quia
• Today you’ll be trying two activities
individually. These are called:
– Organic Molecule Matching
– Organic Molecule Fill-In
• This one is particularly good for test prep and studying.
• You’ll also be doing one as pairs (so put away
one computer when you get here).
– Organic Molecule Challenge Board
Okay, so about energy…
• What do we think of energy? What is it?
What’d you write for the pre-class?
• According to science, energy is the capacity to
do work.
– For our biology class, it might be easier to think of
energy as a force.
– Example: The force (energy) a cell needs to keep
making protein.
Conservation of Energy
• According to the Law of Conservation of
Energy, energy cannot be created or
destroyed.
– In other words, energy can only change form.
• For example, a ball at the top of a hill has a lot
of potential energy. When it rolls to the
bottom, it’s moving nice and fast, and it has a
lot of kinetic energy.
Reaction Example
• Thermite video
• In this reaction, chemical energy from bonds is
changed into thermal energy, which is
released as new bonds form.
Putting it together…
• The reactant(s) are shown on the left of the
reaction equation.
• The product(s) are shown on the right of the
reaction equation.
• The reaction itself is indicated by an arrow (
- say “yields”).
• Example:
• Reactant(s)  Product(s)
• Fe2O3 + 2Al  2Fe + Al2O3
Just checking…
• 2H2 + O2  2H2O
• Which is/are the product(s)?
– H2O
• 2NaCl  2Na + Cl2
• Which is/are the product(s)?
– Na + Cl
Enzyme Review!
• Whiteboards!
• What do you know about catalase or
enzymes?
– What kind of organic molecule?
– What do they do?
– How do they do that?
Some examples…
• Catalase
– Hydrogen peroxide molecules broken into H2O and O2.
• DNA Helicase
– DNA spiral helix shape opened or “unzipped” (breaks
Hydrogen bonds).
• DNA Polymerase
– Polymerizes nucleotides into DNA (forms bonds).
• RNA Polymerase
– Polymerizes nucleotides into RNA (forms bonds).
What’s in a name?
• Enzymes typically end in –ase and the first
part of the name usually describes what it
does.
• DNA Polymerase
– -ase tells you it’s an enzyme.
– Polymer- talks about its action – polymerization!
Enzymes
• Most enzymes are proteins.
• Enzymes speed up reactions that would
otherwise be too slow for life to be efficient.
– They don’t directly speed it up.
– They lower activation energy of a reaction.
• Wait, what’s energy again?
– Energy is “the capacity to perform work.”
– We can think of it as a force.
– Activation energy is the force needed to start the
reaction.
Activation Energy Example
• Imagine you earn an allowance of $1 per week.
• You want to buy a video game system that costs
$349.
– How many weeks do you need?
• 349. Enjoy that.
• If the game system goes on sale for $50, how many
weeks would you need?
– 50.
• So you can get the system sooner, but are you
earning money at a faster rate?
– No.
– This is how enzymes work – they lower the “threshold.”
Threshold?
• In this case, the “threshold” is activation
energy.
• Another way to think of activation energy is by
an example from our chemistry textbook:
– If you roll clay into a thin rope, then shake it
vigorously, eventually the clay will break.
– Similarly, a certain amount of energy is required to
get molecules to “reorganize” themselves and
form bonds. This is activation energy.
Activation Energy
• Enzymes are catalysts because they catalyze
reactions.
– In other words, they “kick-start” ‘em.
Without Enzyme
With Enzyme
Sketch
me!
http://www.saskschools.ca/curr_content/chem30_05/graphics/2_graphics/catalyst1.gif
Sketch
me!
Some other enzyme details…
• Enzymes are typically not used up in a
reaction.
• Enzymes tend to be specific to certain
substrates (reactants).
– What are substrates again?
Substrate
Products
2H2O2 --------> 2H2O + O2
Enzyme
working…
Putting it all together…
• Enzymes affect substrates at the enzyme’s
active site:
http://waynesword.palomar.edu/images/enzyme5.gif
In note form…
• Recyclable
– They don’t get used up in reactions.
• Substrate-specific
– Each enzyme only works on specific reactants.
• Non-Reversible
– Enzymes can either put stuff together or break
stuff apart (but not both).
– In other words, they break or form bonds.
• Active Site
– Where the bonding and “unbonding” happens.
Denaturation
• So what’s your ideal temperature (from the preclass)?
• It turns out that enzymes (and other proteins)
have an ideal set of conditions too.
• If the environment (the body or elsewhere) gets
too hot, they will break or not function efficiently.
Basically, they change shape, and not in a good
way.
• If the environment gets too acidic or basic, or
even too salty, the same thing occurs.
Denaturation
• This process of changing shape, breaking down,
or not functioning efficiently is called
denaturation.
– Typically due to pH or temperature swings.
• In a sentence:
– The small child had such a high fever that some of his
enzymes actually began to denature.
• In an example:
– Protein denaturation is why raw eggs are liquidy and
cooked eggs are solidy.
Enzyme Contest
• I need 3 volunteers and 3 official judges.
• Each volunteer will simulate an enzyme. We’ll
call this enzyme “Splint Splittase.”
• When I say go, you will have 60 seconds to
break in half (and half again) as many wooden
splints as you can.
– Judges will count the total.
Enzyme Contest
• Splint Splittase 1
– You are operating normally. Go!
• Splint Splittase 2
– pH in the body has gotten too acidic. As a result,
your structure has changed. Cross your fingers on
both hands before beginning.
• Splint Splittase 3
– Temperature has gone down. Stick your hands in
ice-water for 60 seconds before beginning.
Enzyme Contest
• Okay, so what was the active site?
– The enzymes’ “hands.”
• What was the substrate?
– Splints.
• And what did you notice about the results?
• Denaturation is a serious problem if it happens in
a living thing.
– The body’s necessary chemical reactions may halt.
– This is why if you get a really high fever you need to go
to the doctor immediately.
One more thing…
• Here’s an off-topic example:
– Let’s say you’re sick and you take a dose of
medicine. You start to feel a better.
– If you were to have taken half a dose, you might
not have felt as good.
– However, taking two doses wouldn’t make you
feel EVEN better than one dose, right?
• So, medicine only helps up to a certain point.
• Similarly, your car can only go so fast.
One more thing…
• You also may have noticed that it didn’t really
matter how many splints I gave the enzymes.
• As long as I gave them enough that they couldn’t
possibly run out, they’d keep working.
• Therefore, in reality, enzymes can only work up to
a certain speed, no matter how much substrate
you give them.
– A small amount of substrate and they may slow down.
– A medium amount of substrate and they’ll work well.
– Lots of substrate? They won’t work any faster.
Enzyme Activity
Enzyme Activity as a Function of
Substrate Availability
Amount of Substrate
Poisons and Enzymes
• Many poisons and drugs (both illegal and
pharmaceutical) work by bonding to enzymes
and staying there.
• Because the active site is taken up, the
enzyme can’t do its normal job.
Enzyme Competition
• Sometimes enzymes are
shut off by competition
with enzyme inhibitors.
– Can be a good thing or a
bad thing…
http://www.elmhurst.edu/~chm/vchembook/573inhibit.html
Real Enzymes
• Some real enzymes to note:
– Amylase: Found in saliva – breaks down
carbohydrates.
– Protease: Found in stomach – breaks down
proteins.
– Lipase: Made by pancreas – breaks down fats.
Enzyme Closure
• For today’s closure:
1. Write the definition of “denaturation” in your
own words in your notebook.
2. Write the word “denaturation” with your fingers
crossed (on your writing hand).
One More Thing…
• We can’t forget to talk about how monomers
are linked together and polymers are broken
apart (digested).
• Two basic chemical reactions are typically the
way living things do this.
– Dehydration synthesis
– Hydrolysis
• Which reaction does what, do you suppose?
Dehydration Synthesis
• Enzyme(s) required.
• Water removed (de-hydration) to put
monomers together (synthesis).
– Results in two linked monomers + 1 extra H2O.
• Dehydration synthesis is sometimes known as
a condensation reaction because water is a
by-product.
Dehydration Synthesis
• Forming a glycosidic bond:
http://staff.jccc.net/pdecell/biochemistry/sucrosesyn.gif
Dehydration Synthesis
• Forming a peptide bond:
http://img.sparknotes.com/content/testprep/bookimgs/sat2/biology/0003/peptide.gif
Synthesis of Disaccharides
• With your lab group, build any two of the
following monosaccharides:
– Note the difference in shape, but not elements.
Carbon = Black 4-peg | Oxygen = Red 2-peg | Hydrogen = White 1-peg
Synthesis of Disaccharides
• Now, take your two carbohydrates and
remove an H from one and an OH from
another to join them.
Carbon = Black 4-peg | Oxygen = Red 2-peg | Hydrogen = White 1-peg
Dehydration Synthesis Example
http://bio1151.nicerweb.com/Locked/media/ch05/05_05Sucrose.jpg
Synthesis of Polysaccharides
• Now that you have a disaccharide, attach your
disaccharide with another group’s, making a
small polysaccharide.
– Use the same dehydration process as before.
Hydrolysis
• Enzyme(s) required.
• Water added (hydro-) to break polymers apart
(lyse).
– Results in a monomer or two, minus 1 H2O.
• How to remember?
– Hydrolysis: “Hydro-slices”
Hydrolysis
http://2.bp.blogspot.com/_GsPuGchS5Fg/So7giHvBKCI/AAAAAAAAAIY/7gWtmgiNQ4s/s1600-h/c8.8x13.hydrolysis.sucrose.jpg
Hydrolysis
• Using the reverse process as before, use
hydrolysis to break down the molecule into
individual monosaccharides again.
Carbon = Black 4-peg | Oxygen = Red 2-peg | Hydrogen = White 1-peg
Conceptually
• Dehydration synthesis:
H2O
• Hydrolysis:
H2O
Molecularly
• Dehydration synthesis:
• Hydrolysis
Closure
• Work on the half-worksheet called “Enzyme
Reactions.”
Closure
• BBC – Bitesize Enzymes
Homework
• Watch/read this animation:
– http://www.sumanasinc.com/webcontent/animati
ons/content/proteinstructure.html
– Also available by Googling protein structure egg.
• First result…
– Also available as a link from my website: Eggs and
Protein Structure.