1. Activation Energy … is the amount of energy needed to start reaction
In order to speed up reaction, catalysts are used
Enzymes are catalysts in cells. @

3. holo enzyme (active enzyme)
active site
Non-protein part can be a cofactor or a coenzyme. It is the part which makes an enzyme active.
non-protein part
protein
apoenzyme
Cofactor
inorganic
ex: zinc, iron, potassium, copper
Coenzyme
organic
ex: vitamins, NAD, FAD, NADP+ @

4. Enzymes… Are made up of proteins
Simple Enzymes: only made up of proteins.
Complex Enzymes: are made up of proteins + non protein part

5. Structure of Enzymes… Two major parts: Protein part:
Apoenzyme : made up of protein.
not catalyze the reaction by itself
has to interact with non protein part
Non- protein part :
Coenzyme: made up of organic molecules (vitamins)
Cofactor: made up of inorganic molecules (K, Ca ) + +

6. Structure of Enzymes… Lock and key
Substrate:The molecule which enzyme acts on
Active site: Specific region on the enzyme that substrate binds
Enzyme –Substrate Complex
Lock and key

7. One apoenzyme works with only one coenzyme or cofactor
Enzymes are not changed or used up
The same enzyme works for the forward and reverse of the reactions
Lipid +H2O Fatty Acids +Glycerol
Lipase

8. Properties of Enzymes Specificity:
Enzymes work with only one type of substrate
Final molecule of the reaction is product
Not used up, destroyed at the end of reaction
Can be used over and over until destroyed by other factors (heat)

9. Properties of Enzymes…
Reversibility
Catalyze reactions for forward and reverse directions
Not determine direction
Ratio of equilibrium
Only digestive enzymes catalyze reaction in one way
Naming
According to molecules they act :
-ase
Exp: Lipase, Amylase or
Pepsin, Tripsin
According to type of reaction catalizing.

10. Properties of Enzymes…
The exact point of effect
Surface of area
Wider surface
Greater rate of reaction
Speed
Speed up reaction
Without enzyme breaking down takes more time

11. Properties of Enzymes…
Work in Teams
the product of one reaction catalyzed
The substrate for another enzyme
Place of synthesis
Apoenzyme part is protein, so synthesized in ribosomes just like proteins
Gene destroyed
Enzyme not synthesized
Cell dies
Maltase
Amylase
Starch
Glucose
Molecules
Maltose
Molecules

12. Enzyme-substrate complex (temporary)
There are two models that provide explanation to enzyme action:
Lock and Key Model: The substrate(s) fits exactly into the active site of the enzyme. @
E S
E – S
E P
Enzyme
Substrate
Enzyme-substrate complex (temporary)
Enzyme
Product

14. 2. Induced Fit Model: @
In this model, the enzyme has no rigid shape. Instead the enzyme changes shape slightly as the substrate enters the active site. Once it has changed shape, the enzyme fits tightly around the substrate As the enzyme embraces the substrate it can weaken the chemical bonds in the substrate, which helps the reaction to proceed.
The enzyme changes shape slightly to grasp the substrate at the active site.

15. Characteristics of Enzyme Action:@
Small amounts of an enzyme can cause the reaction of large quantities of substrate.
- The time needed for an enzyme-substrate complex to form and a reaction to occur is very short.
- A simple enzyme molecule can catalyze thousands of substrate reactions in a second.

16. 2. Enzymes enable cell reactions to take place at normal temperatures.@
enzyme activity
Optimum temperature for many enzymes (about 36oC)
temperature (oC)

17. At OoC, enzymes do not function although their structure is not changed (they are not denaturated).
The temperature at which an enzyme is most effective is called the optimum temperature of an enzyme. At their optimum temperature values enzymes work best.
At higher temperatures (like 55oC) enzymes are denaturated and they lose their properties. So they cannot catalyse a reaction.

18. 3. Each enzyme works best at a certain pH.
Optimum pH for pepsin
enzyme activity
Optimum pH for many enzymes
Optimum pH for trypsin pH
The effectiveness of an enzyme depends on the pH of medium.
Each enzyme works at different pH values.

19. 5. Some enzymes need substances called activators in order to function.
Activators are coenzymes or cofactors.
6. Some enzymes function inside the cell, others act outside of the cell. Ex: pepsin

20. 7. Inhibitors stop or slow down the activity of enzymes.
Antibiotics, pesticides, herbicides, heavy metal ions (Pb+2, Hg+2, Ag+2 ), CO, snake and scorpion poisons, CN, Cu
They slow down or stop the activity of enzymes

21. Inhibitors
Competitive
Non - Competitive
Those inhibitors compete with the normal substrate in attachment to the active site
They have an influence on the protein part of the enzyme apart from the active site

23. Enzyme activity
enzyme + activator
enzyme
enzyme + inhibitor
Concentration of inhibitor or activator

24. 8. Amount of water affects the enzyme activity.
If a medium contains less than 15% water, then the enzyme activity stops.
9. Substrate surface
Enzyme action begins from the substrate surface.
Therefore, increasing surface area of substrate increases the rate of recation until a maximum rate is reached.
rate of reaction
surface area