1.7 Enzyme action Flashcards
(14 cards)
What is an active site (only use this term for enzymes)
*A small part of an enzyme that attaches to a substrate to catalyse a reaction
*It is specific and unique in shape due to the specific folding and bonding in ther tertiary structure of the protein
How do enzymes act as biological catalysts
*Each enzyme lowers the activation energy of a reaction
*To speed up the reaction without getting used up
*Provide an alternative pathway with a lower activation energy
What does the Lock and Key model suggest (4)
- The active site is a fixed shape and due to random collisions the substrate can collide and attach to the enzyme
- forming an ENZYME SUBSTRATE COMPLEX
- Once they are in the ENZYME SUBSTRATE COMPLEX it will cause the substrate to slightly distort in shape lowering the activation energy
- After the substrate distorts in shape the products are then released and the active site is empty and ready to be reused
What is the analogy used for in the induced fit
The enzyme is a glove and the substrate is your hand
Explain the glove and hand analogy of the inducing fit
A glove is not exactly complimentary to your hand but when your hand enters it enables the glove to mold around your hand to become completely complimentary
Describe the induced fit model of enzyme action (4)
- Substrate binds to (not completely complementary) active site of enzyme
- Causing active site to change shape (slightly) so it is complementary to its substrate
- So enzyme-substrate complex forms
- Causing bonds in substrate to distort, lowering activation energy
Why are enzymes effective in small quantities
They can be reused repeatedly
What are the conditions required for a reaction (between enzyme and the substrate) (3)
- Reactants (substrate) must collide with sufficient energy to alter the arrangements of their atoms to form the product
- The free energy of the products must be less than that of the reactants
- The activation energy must be reached
Free energy= The energy available in a system to do work
Define activation energy
The minimum amount of energy required for a reaction to take place
What is the significance of enzymes?
Lower temperatures
Allows reactions to take place at a lower temperature than normal
This enables some metabollic processes to occur rapidly at 37*c
What happens if you change certain amino acids that are not a part of the active site
It prevents the enzyme from functioning as the changed amino acid could be the one that forms hydrogen bonds leading to a change in the tertiary structure
Describe how models of enzyme action have changed overtime
Initially lock and key model where it stated that the active site was a fixed shape and complementary to one substarte
Now it is induced fit model
Explain the specificity of enzymes (4)
● Specific tertiary structure determines shape of active site
○ Dependent on sequence of amino acids (primary structure)
● Active site is complementary to a specific substrate
● Only this substrate can bind to active site, inducing fit and forming an enzyme-substrate complex
What is a limitation of the lock and key model
The enzyme is ocnsidered to be a rigid structure and could only bind to one point
However enzymes can bind to sites other than the active iste
Strcutre is fexible
