1. Chemical Reactions & Enzymes
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Chemical Reactions & Enzymes

2. A chemical reaction is a change in which one or more substances are converted into new substances.
A + B C + D
The substances that will be reacting together are called reactants.
The substances that are produced are called products.

3. Chemical reactions where the reactants release energy, often occurs almost instantly.
2H2 + O2 → 2H2O
Burning hydrogen gas
Oxygen gas
Water
Exothermic reaction
Chemical reactions where you have to add energy to the reactants will not happen unless you add energy to it.
Burning hydrogen gas
Oxygen gas
Water
2H2O → 2H2 + O2
Endothermic reaction

4. So how much ENERGY does it take to start a chemical reaction?
Energy is used to create chemical reactions no matter which method is used.
Energy +
Energy changes into… or forms. C A B
Reactants
Products
You have to put energy into the equation to get a reaction to work
So how much ENERGY does it take to start a chemical reaction?

5. The amount of ENERGY needed to start a chemical reaction is called the ACTIVATION ENERGY
If not enough energy is added, the ball cannot reach the Activation Energy level and there is NO REACTION.
If enough energy is added, the ball reaches the Activation energy level and the Chemical Reaction Occurs

6. Chemical A Chemical C Chemical B
(Reactant)
Activation energy
Chemical B
(Product)
(Reactant)
When the reaction occurs, ENERGY is RELEASED because the ENERGY is changing forms.

7. Energy Released B A
Product

8. ENZYMES

9. (which breaks down proteins like in a steak that you eat)
ENZYMES are proteins that help speed up a chemical reaction.
Another word for this (speed up reaction) is called CATALYST
A great example of an enzyme is in your stomach with the enzyme Pepsin.
(which breaks down proteins like in a steak that you eat)

10. When you eat, your food is still too big to digest properly.
Your stomach can’t absorb the food this way

11. Your stomach releases an ENZYME called PEPSIN, which breaks down the food proteins into small monomers which the body absorbs for energy.

12. If you didn’t have this enzyme, the stomach acids would take days for it to dissolve the food into smaller pieces.
What happens if you don’t eat for days?
1. You’re sluggish / no energy
2. Body systems start to shut down
3. Leads to illness

13. How does it do it? – It lowers the
So the enzyme PEPSIN, speeds up the chemical breakdown of proteins in our food.
How does it do it? – It lowers the
ACTIVATION ENERGY

14. Energy Released B A
Product
Remember this?

15. Pepsin lowers the activation level like this.
Energy Released B A
You don’t need as much energy!!!

16. ENZYMES:
Speed up a reaction
Lower Activation Energy.
Are reusable?
Yes, enzymes can be used over an over and over like re-chargeable batteries.
Let’s look at the enzyme “Pepsin” up close…

17. The reactant it attaches to is called a *SUBSTRATE*
Pepsin attaches one of the reactants (protein)
The reactant it attaches to is called a *SUBSTRATE*
Where it attaches is called the “Active Site”
Substrate (protein)
Active site
Pepsin
PEPSIN

18. Note how the curves fit perfectly together…
Pepsin is very specific for one Substrate only! (Just like only 1 key can fit a lock) All enzymes are specific
Note how the curves fit perfectly together…
Substrate
PEPSIN
Pepsin

19. Enzyme-Substrate Complex
When the enzyme and substrate join together, it gets a new name called the:
Enzyme-Substrate Complex
Substrate
Pepsin
PEPSIN
PEPSIN
This is when the chemical reaction occurs!

20. Notice that the lock & key curves are the same, yet the chemical reaction makes the new products in that same space.
Pepsin

21. After the chemical reaction, the new Products (proteins) are made and the Pepsin looks for more Substrate to break down.
Pepsin

22. The Process Simplified…
Pepsin
Pepsin
Pepsin + +
Enzyme + Substrate Enzyme Enzyme + Product(s)
SubstrateComplex
E + S ESC E + P

23. Since enzymes are specific for a certain substrate, there are many enzymes in your body.
Enzymes were originally named with a “-in” ending (Pepsin).
Later on, scientist started naming the enzymes with a “-ase” ending
Since Carbohydrate sugars are named with a “-ose” ending, there is a enzyme that is specific for each one.

24. SUGAR NAME
ENZYME NAME
Lactose
Lactase
Sucrose
Sucrase
Maltose
Maltase
What I want you to remember from this is:
Sugars – have “ose” endings
Enzymes – have “ase” endings

25. What could cause enzymes not to work properly?
When an enzyme doesn’t work properly it is said to be Denatured - the active sites on an enzyme change in shape, therefore unabling the enzyme to lock up with a substrate
Pepsin

26. Causes of Denaturation are:
1. Too high of Acid or Base (pH) in your body
2. Temperature differences (hot / cold) fever, chills
Pepsin
3. Lack of Water / Oxygen

27. One of the most important reactions in your body involves the enzyme Catalase.
Catalase turns the cell waste product of Hydrogen Peroxide (H2O2) into Water and Oxygen gas.
The reaction is: 2H2O2 ----> 2H2O + O2 (fix)
Hydrogen
Peroxide
---->
Water
Oxygen Gas