Enzymes Flashcards
What is the lock and key hypothesis?
This is when the substrate and active site are completely complimentary to each other.
What is the induced fit hypothesis?
This is when the active site is not initially complimentary but it then moulds around the substrate to make an enzyme substrate complex.
Define anabolism
Anabolism is the chemical reaction where bonds are formed
Define catabolism
Catabolism is the chemical reaction where bonds are broken
Define the activation energy
The amount of energy required to allow for a chemical reaction. The energy is acquired from the surroundings.
What is the difference between the active site in the lock and key vs induced fit theory?
The active site in the lock and key theory is rigid and complimentary vs the induced fit theory active site is flexible and initially not complimentary.
Can enzymes be reused after a reaction?
Yes enzymes can be reused after a reaction if they are not denatured.
What are enzymes?
Enzymes are globular proteins that catalyse a metabolic reaction
What two processes make up metabolic reactions.
Anabolism and catabolism
What gives the enzyme is catalytic ability?
Its tertiary structure
Where does the substrate act on the enzyme?
The active site
Give 4 examples of factors which affect enzyme reactions…
- Temperature
- pH
- Substrate concentration
- Enzyme concentration
How does low temperature affect enzyme activity?
Low temp - less kinetic energy in the molecules, resulting in fewer collisions between the substrate and enzyme active site. Therefore the enzyme is inactive
What happens to the rate of reaction as the temp increases?
Increase in kinetic energy, means an increase in the rate of reaction until it reaches its optimum temperature.
What happens to the rate of reaction as the temp increases?
Increase in kinetic energy, means an increase in the rate of reaction until it reaches its optimum temperature.
Describe what happens to the rate of reaction once the temp is greater than the optimum
rate of reaction decreases, the enzyme has been denatured, the hydrogen and ionic bonds within the tertiary structure are broken which causes the active site to lose its complimentary shape.
How is the rate of an enzyme catalysed reaction measured?
The amount of substrate changed / product formed over a period of time.
At what pH does maximum enzyme activity occur?
optimum pH (this will vary from enzyme to enzyme)
How does pH affect the activity of the enzyme?
Changes to pH will alter the active site of the enzyme
What is pH?
pH is the measurement of hydrogen ion concentration
How does hydrogen concentration affect enzymes?
Hydrogen concentration changes the charge on R groups which alters the amino acids and the ionic bonds are affected
Fill in the blanks:
At non-optimal pH the ____ attaches less readily to the _____
Substrate
enzyme active site
At minor pH changes, denaturation is reversible. True or false - explain:
True
ionic bonds can reform
At extreme pH changes, the denaturation is permanent. True or False
True
Define the saturation point
All active sites are occupied. Increasing substrate concentration will not change the rate of reaction
How does increasing substrate concentration affect the rate of reaction? (3)
- Rate of reaction increases
- Substrate levels are increased - (these are normally limiting factor)
- More enzyme-substrate complexes formed
What are enzyme inhibitors?
Substances that interfere with the activity of the enzyme either directly or indirectly
Where do competitive inhibitors act?
Compete with the substrate for the active site. (they have a similar shape to the substrate)
Describe the effect of a competitive inhibitor:
Rate of reaction decreases. Less enzyme-substrate complexes formed because competitive inhibitor will fill the active sites.
Describe the action of a non- competitive inhibitor:
Binds to the enzyme somewhere other than the active site, changes the shape of the active site. It is no longer complimentary to the substrate. The enzyme can no longer form a catalytic reaction.
Does increasing the substrate concentration increase the rate of reaction when there are non-competitive inhibitors present? (3)
No
The active site has changed and the substrate is no longer complimentary
Substrate concentration will not affect the rate of reaction.
What are the methods of immobilisation (5)?
Adsorption Covalent bonding Cross-linking Encapsulation Gel entrapment
Describe 1 advantage of adsorption: [1]
Easy to immobilise - cheap
Describe 2 disadvantages of adsorption [2]
Enzymes can be washed away
Some active sites may be blocked
Give one example of a material that may undergo adsorption:
Glass
Describe 2 advantageS of covalent bonding:
Resistant to pH and temperature changes
Enzymes are not washed away
Describe 2 disadvantages of cross-linking:
Disorientation of active site
Active sites may be blocked
Give one example of a material that may undergo cross-linking:
Glutaraldehyde
Describe 2 disadvantages of covalent bonding:
Expensive
Active sites my be blocked by support material
Give 1 example of covalent bonding:
Cellulose
Give 2 advantages of encapsulation:
Active sites aren’t blocked
Activity isn’t affected
Describe 2 disadvantages of encapsulation:
Some enzymes may leak out through mesh
Substrate has to diffuse through mesh
Give 1 example of encapsulation:
Nylon
Describe 2 advantages of gel entrapment:
Enzymes cannot leak out
Enzymes are not bound - active sites not blocked
Describe 1 disadvantage of gel entrapment:
Resistant to substances diffusing into and out of a gel matrix
Give an example of a material that will undergo gel entrapment:
Alginate
What is the role of biosensors?
Use immobilised enzymes to detect/ monitor a particular molecule
What is the role of biosensors?
Use immobilised enzymes to detect/ monitor a particular molecule
What is an enzyme co - factor?
A small non-protein substance
What is the role of a co-factor?
Acts as a bridge - between enzyme and substrate
Contributes directly to catalysis
What are co - enzymes?
Small organic molecule
Can co-enzymes be reused?
Yes again and again
What will occur if co-enzymes are covalently bonded?
Forms a prosthetic group or a conjugated protein
What is a co-enzymes main function?
catalytic function
What is a co-enzymes main function?
catalytic function
