1. Proteins Making Chemical Reactions Possible
Enzymes
Proteins Making Chemical Reactions Possible

2. Energy and chemical reactions
Most chemical reactions require energy to begin
- the energy required to start a chemical reaction is called activation energy.

3. What are enzymes?
Enzymes are proteins which reduce activation energy allowing chemical reactions to occur in living things

4. Enzymes reduce activation energy

5. Enzymes Act as Biological Catalysts
Catalysts are inorganic molecules that speed up chemical reactions
- catalysts remain unchanged by the reaction that they speed up.
-one molecule of catalyst can catalyze (start) many
chemical reactions
Enzymes speed up reactions in living things
-enzymes are not changed by the reaction they speed up
- one molecule of enzyme can catalyze (start) many
reactions

6. Active Site Enzymes have an area called an active site.
- the active site is where the chemical reaction occurs

7. The Shape of the Enzyme Determines Function
The active site of the enzyme fits with only one type of molecule known as the substrate.
Substrate is the molecule that the enzyme acts on.
The fact that the active site can only accept one type of substrate is known as enzyme specificity

8. Enzyme Reactions Catalase + 2H2O2 ES Catalase + 2H2O + O2 Written as :
Enzyme + Substrate ES Enzyme + Product
- ES refers to the enzyme substrate complex, the time when the substrate joins with
the active site.
Example
Catalase + 2H2O ES Catalase + 2H2O + O2
enzyme substrate enzyme enzyme product product
substrate
complex

9. Two Ideas About Enzyme Action
Lock & Key Model Induced Fit Model

10. Lock & Key Model
Substrate fits into the active site like a key into a lock
The enzyme puts stress on the
bond which reduces the amount
of energy needed to break apart
the substrate
The products of the reaction
leave and make the enzyme
available for more substrate

11. Induced Fit Model Substrate doesn’t quite fit into the active site
Substrate causes (induces) the enzyme to
change shape – allows the substrate to fit into the active site
Enzyme stresses bonds
on substrate

12. Enzymes can build molecules
Substrate molecules can only bond one way. Substrate molecules fit into the active site in the best position to bond Once in the active site, the molecules of substrate join

13. Enzyme Inhibitors Inhibitors control the rate of enzyme activity
- if there is too much of an enzyme’s product, inhibitors can slow or even stop an enzyme’s activity
Two types of Inhibition
- Competitive Non Competitive

14. Competitive Inhibition
The inhibitor is a molecule that can occupy part of the active site
While the inhibitor is in the active site, substrate can’t bind with the enzyme – inhibitors compete with the substrate for the active site
inhibitor competes with substrate inhibitor blocks the active site

15. Noncompetitive Inhibition
The inhibitor binds with the enzyme at a site away from the active site.
Inhibitor causes enzyme to change shape – prevents
substrate from entering the active site
Inhibitor binds with enzyme Enzyme changes shape keeps
substrate from active site

16. Feedback Inhibition
Enzymes are often part of a series of reactions called a biochemical pathway
- the product of one enzyme acts as the substrate for another enzyme
-the final product – acts as an inhibitor for the first enzyme in the pathway
- this stops the pathway and the production of the end-product stops as well

17. Feedback Inhibition When the concentration of the end-product drops
to a low level, inhibition ends
and the enzyme pathway
resumes operation
The end-product of the
pathway is used for other
purposes
As the end-product is
used, its concentration
drops

18. Co-Enzymes and Co-factors
Co-enzymes and Co-factors are molecules that help certain enzymes to catalyze a reaction
- co-enzymes and co-factors often act as carriers of electrons, atoms or functional groups needed to complete a reaction.

19. Co-Enzymes and Co-Factors
- while they bind to an enzyme’s active site, and participate in the reaction, they are not changed by the reaction and aren’t considered substrates.
- Co-enzymes are organic molecules and include: NAD, NADP, FAD, vitamin B 1, vitamin B 6, and vitamin B 12
- Co-factors are inorganic molecules and include dietary minerals like zinc, iron, copper & potassium

20. Denatured Enzymes
Enzymes are proteins and if they are exposed to extremes of temp or pH lose their shape
- if a protein loses its shape, it loses its function
- a protein that loses its shape is said to be denatured
- if an enzyme is denatured, substrate can’t enter the active site
extreme
temp or pH

21. Common Enzymes Amylase - breaks down starch
Catalase – breaks down H2O2
DNA polymerase – joins DNA nucleotides to build DNA
Lipase – break apart fats
Lactase – breaks apart lactose – milk sugar
Protease- breaks apart protein molecules
-What does –ase in a molecules’ name imply?

22. Vocabulary for Enzyme Excitement
Enzyme Competitive Inhibition
Activation energy Non Competitive Inhibition
Catalyst Denatured Protein
Active site Feedback Inhibition
Substrate Biochemical Pathway
Enzyme specificity co-enzyme/co-factor
Lock & Key Model
Induced Fit Model
Enzyme inhibitor