ENZYMES
are globular proteins that catalyze reactions without being consumed themselves
Why are enzymes essential to life
Because they allow chemical reactions to occur rapidly and efficiently without having to increase the temperature in the system
Each reaction is catalyzed by
its own unique/ specific enzyme
SUBSTRATE
is a REACTANT acted upon by an enzyme is called the SUBSTRATE of that enzyme.
What does the activity or specific function of an enzyme dependent on
it depend on its 3D shape ( tertiary structure)
Generally, How is the name of an enzyme formed
by addidding “ ase” to the name of its substrate
ACTIVE SITES
An enzyme molecule contains one more active sites where the SUBSTRATE fits
DENATURED
The shape of the enzyme is altered- it no longer is functional
EQUATION OF ENZYMATIC REACTIONS
ENZYME + SUBSTRATE ENZYME SUBSTRATE COMPLEX —–> ENZYME + PRODUCT
The variable that remains unchanged in a enzymatic ration is
THE ENZYME
What happens to the enzyme at the end of a reaction
The product is released and the enzyme returns to it original shape
Since all enzymes speed up the conversion of some substances(SUBSTRATE) into a product. How we study the activity of the enzyme
by detecting production of the product ( since only THAT enzyme can cause THAT PRODUCT to be produced
Why do some plants and vegetables turn burn if peeled or sliced
It is due to the formation of a class of compounds called QUINONES by the damaged plant.
The purpose of QUINONES in potatoes ( for example)
They protect the interior of the potato from invasion by soil microorganisms if the skin of the potato is damaged.
Molecules of quinones collect in the area of the damage and form a brown patch that
- seals the break
- is toxic to microorganisms
How does QUINONES protect the plant
Molecules of quinones collect in the area of the damage and form a brown patch that
- seals the break
- is toxic to microorganisms
High concentration of QUINONES is also toxic to plant cells. What mechanism do plants have that make quinone only after the plant skin is damaged.
In addition to cellulose the cell walls also contain CATECHOL
in its chemically reduced form ( gained electron) what does CATECHOL look like
It is colorless
What happens to CATECHOL in the presence of oxygen
It will oxidize to QUINONE
What is the purpose of POLYPHENOL OXIDASE (PPO)
It is an enzyme that catalyses the oxidization of CATECHOL to QUINONES
How does PPO work
- In an undamaged potato PPO remains inside the cells (in the cytoplasm) with the CATECHOL outside.
- When the potato cells are damaged the cytoplasm leaks out, allowing the PPO to come in contact with the CATECHOL on the outside and catalyze its conversion to QUINONE
What is the equation for the QUINONE PRODUCT
PPO( enzyme) + CATECHOL( substrate) ENZYME- SUBSTRATE COMPLEX —> PPO (enzyme) + QUINONE ( product/ brown)
How can the activity of any enzyme be measured
by detecting the product of the reaction catalyzed by the enzyme
QUINONE is a yellow/ brown liquid, its formation indicates
a reaction has occurred. PPO catalyzed CATECHOl to produce QUINONE
Why is QUINONE in its entirety darker than its individual molecules that are a faint copper colored molecule
A solution of QUINONE is proportional to its concentration. The darker the solution, the more product present
In the experiment why are the potatoes blended
to open up lots of potato cells
Why is the blended potato poured through 4 layers of cheese cloth
To remove most of the starch
The extract turns brown why
- once the cells are broken the PPO comes in contact with the CATECHOL and become QUINONE a brown color.
- The CATECHOL is used up in the solution to make QUINONE but soon after this product is made PPO IS free to catalyze waiting for more CATECHOL
Why does increasing the amount of PPO not increase the rate of the reaction
There are specific amounts of active sites per substrate. Adding more PPO will not make a difference unless more substrate is added
