1. Chemical Reactions and Enzymes
Standard 1.3

2. Chemical Reactions
Changing one set of chemicals into different chemicals.
Configuration of elements in molecule or compound is changed, not the kind of elements
Many chemical reactions require energy to occur.
Some chemical reactions release energy.

3. Chemical Reactions
Reactants- the molecules or compound that are changed in a reaction.
Products- the resulting new molecules or compounds
Reactants  Products
Yield (shows the direction of the reaction)
2H O2  H2O
Reactants Products

4. Learning Check
In the following chemical reaction, which set of chemicals are the reactants?
C6H12O6 + O2  CO2 + H2O
C6H12O6 + O2

5. Activation Energy Activation Energy The amount of energy
needed to start a
chemical reaction
Catalyst
Lowers the activation energy of a reaction, speeding up the rate of the reaction

6. Learning Check What is activation energy?
The energy needed to stop a reaction.
The energy needed to start a reaction.

7. Enzymes
Enzymes are catalytic proteins: (proteins that act as catalysts) change the rate of reactions in living things without being consumed (used).
Activation Energy (EA) is lowered causing the reaction to happen faster

8. Learning Check
When activation energy is lowered the rate of the reaction
Stops
Increases
Slows down
Stays the same

9. Enzyme-substrate complex
Substrate- the reactants of a chemical reaction that uses an enzyme to occur
Active site: pocket or groove on enzyme that binds to substrate

10. Enzyme-substrate complex
Substrates are converted to products
Enzyme remains unchanged and is released to find more substrates

12. Learning Check
What happens to an enzyme after it catalyzes a reaction?
It is broken down
It is unchanged and finds more substrate
It becomes part of the product
Nothing

13. Enzyme Action
Highly specific- one enzyme for each substrate or set of substrates
Substrates bind to the active site of the enzyme where the reaction occurs

14. Lock and Key
Just like there is only one key shape for each lock, there
is only one type
of enzyme for
each type of
substrate.
Substrate
Active Site
Enzyme

15. Enzyme Action

16. Learning Check What does it mean that enzymes are “highly specific?”
A. There is only one kind of enzyme for each kind of substrate.

17. Regulating Enzyme Activity
Enzymes depend on certain conditions to work
Homeostasis- all have optimum (best) temperature and pH.

18. Proteins (enzymes) will be denatured if conditions are not perfect and will stop working.

20. Learning Check
What kind of conditions would cause an enzyme to denature and stop working?
pH too high
pH too low
temperature too high
All of the above

21. Inhibitors
Some enzymes are inhibited by competitors (look and act like substrates without reacting).
Keeps enzyme catalyzed reactions under control

22. Some enzymes must be activated by another protein before they can bind to their substrates
Activator
Substrate

23. Naming Enzymes 1. Enzymes are named for the reaction the catalyze.
Lactase is the enzyme that helps break down lactose.
2. -ase: Almost all enzymes end in the suffix
–ase
Examples: Amylase, DNA polymerase, catalase

24. Learning Check
When naming enzymes, what three letters are usually used as a suffix?
-ose
-ase
-aes
-yme

25. Summary
Many chemical reactions require energy to occur. This is called activation energy.
Enzymes are proteins that lower the activation energy of a reaction, make the reaction happen faster.
Enzyme are highly specific, working only with certain substrates, and working only at optimum conditions.