Transcript Ch. 2.4 and 2.5

Section
2.4 &2.5:
Enzymes
To the penny placed on your desk.
1. Observe the penny but don’t touch it. What happens?
– Explain why
2. Give the penny a little push. What happened?
– Why did the penny move the second time and not the
first time?
– What was added the second time and not the first
time?
Chemical Reactions Release and Absorb Energy
• Energy is neither created or destroyed, it
continues to be transferred.
Potential Energy
Potential Energy
Potential to
Kinetic Energy
• All Chemical reactions involve a
change/transfer in energy.
Potential Energy
Observing a Chemical Reaction
1. Put 50 mL of water into a flask
2. Add 10 drops of Bromothymol Blue (an acid
indicator which will turn the solution yellow if an
acid is present)
3. Get the temperature in `C.
4. Add one Alka Seltzer tablet (split into two)
5. Observe reaction and write down observations
6. Get the temperature after the reaction occurs.
What you observed was:
CO2 + H2O
H2CO3 (Carbonic Acid)
Reactants
Product
Energy is needed to start a Chemical Reaction
Activation Energy is the amount of energy that
needs to be absorbed to start a chemical
reaction
– The push to get the boulder to go down the hill
Activation Energy
Do you have this bottle at home?
1. What is it? Hydrogen Peroxide
2. What is it used for? Disinfecting a wound
3. Can you keep it in your medicine cabinet
forever? NO!!
4. Why? It will naturally break down into Water
and Oxygen
What happened when the Manganese Dioxide was
added to the 3% Hydrogen Peroxide?
What happened when the Manganese Dioxide was
added to the 30% Hydrogen Peroxide?
How can we reduce the amount of activation energy
needed to get a reaction started?
2H2O2
2H2O + O2
– This reaction will occur on its own but will take a long time
and a lot of activation energy
– Catalysts reduce the amount of activation energy necessary to
get a reaction started
– This is a method of cleaning contact lenses using a Manganese
dioxide disk which will quickly break hydrogen peroxide into
water in oxygen and get your contacts totally disinfected!!
• The Manganese dioxide disk can be used over and over again without a
loss of functioning.
A Chemical Reaction with and without a catalyst
a catalyst
a catalyst
• The Catalyst decreased the amount of activation
energy needed to get the reaction started
Does anyone suffer from eating…?
…Beans, peanuts, broccoli, cauliflower, Brussel
sprouts, cabbage, peppers, onions…?
• You know what I am talking about!!!
• This happens because we can’t digest
alpha-galactose present in these foods
• There is something to prevent this!!
• Beano contains the Enzyme alpha-galactosidase
to allow us to break down alpha-galactose
What is the name of the sugar found in milk? Lactose
Maybe you can’t tolerate lactose sugar and are lactose
intolerant.
What do people do who are lactose intolerant?
They take Lactaid pills which contain the enzyme
Lactase
We will do a lab on this
Enzymes are protein catalysts made by living
organisms that reduce the amount of activation
energy necessary to start and control the rate of a
chemical reaction
Our cells always produce Hydrogen Peroxide.
2H2O2
2H2O + O2
This is highly toxic to our cells.
An enzyme called catalase will allow hydrogen
peroxide to quickly break down to water and
oxygen.
You have seen this with a cut and blood when you
put hydrogen peroxide on it.
One catalase molecule can convert 40 million of
molecules of hydrogen peroxide to water and
oxygen each second
Characteristics of Enzymes
1. Made up of Proteins
2. Are specific to whatever they act upon
3. Are reusable – don’t get used up in a
chemical reaction
4. Usually have names ending in “ase”
5. Enter directly into a reaction
How Enzymes work
• Their shape is specific to what they act upon
(the substrate)
• They will bind directly to the substrate as an
enzyme-substrate complex
• The binding site is called the Active Site
• A substrate and its enzyme fit together like
puzzle pieces – Lock and Key Theory
Substrate
What can influence an enzymes reactivity?
1. Temperature
Since enzymes are proteins, their structure can be
changed or destroyed by high temperatures.
As temperature increases, the rate of enzyme activity
increases to a point then quickly decreases.
Study Island Virtual lab
In us, this temperature is at ~ 40`C
2. pH
Too high or too low pHs will effect the enzyme
activity and possibly change its shape.
Lactase activity virtual lab
Different for different organs
3. Concentration of enzymes
As the number of enzymes increases, the rate of
reaction increases also to a point where all the
enzymes are already bound to an active site of a
substrate.
Additional enzymes won’t speed up a reaction at
this point.
Review
1. To which biomolecule group do enzymes belong
to and usually end in …?
Proteins, -ine
2. What is an enzyme?
Organic catalyst
3. What do enzymes do?
Controls the rate of a reaction
4. What part of the enzyme enters into a reaction?
Active Site
5. What is the term used for the molecule which is
acted on by the enzyme?
Substrate
6. When the two are together, what is it now
called?
Enzyme-Substrate Complex
7. What will extreme pH’s and temperatures do to
the active sites of enzymes?
Denature the active site – Change the shape
8. What is the ideal pH and temperature for most
reactions in our body?
~6.5 – 7.4 & 37`C
Label the diagram using the terms, Product, substrate,
enzyme, active site and, enzyme-substrate complex.