Enzymes Flashcards
(22 cards)
Define metabolism
Metabolism is a combination of catabolic and anabolic reactions that are catalysed by enzymes.
What is anabolism?
The process where anabolic reactions build larger products from smaller substrate molecules.
What is catabolism?
The process where catabolic reactions break larger substrate molecules into smaller products.
What is an enzyme?
An enzyme is a globular protein and biological catalyst that can increase the rate of reaction by lowering the activation energy of a metabolic reaction.
Define intracellular
An enzyme that acts within cells
Define extracellular
An enzyme that is secreted by cells and functions outside of them.
Define activation energy
The minimum amount of energy that is required for an chemical reaction to occur.
What is the induced fit model?
Where the substrate molecule changes the shape of the active site so that the enzyme and substrate are complimentary to one another.
What factors affect the rate of enzyme controlled reactions?
Temperature
pH
Enzyme Concentration
Substrate Concentration
How does temperature affect the rate of enzyme controlled reactions?
As the temperature increases, the rate of reaction also increases as the molecules gain kinetic energy, moving more rapidly increasing the chances of a successful collision leading to the formation of more enzyme-substrate complexes.
How does pH affect the rate of enzyme controlled reactions?
Small changes in pH=reversible changes
Extreme changes in pH=denature the enzyme
If there are too many H+ or OH- ions present the enzyme and substrate molecule will repel one another. Thus decreasing the rate of reaction and product formation.
How does enzyme concentration affect the rate of enzyme controlled reactions?
The rate of reaction is directly proportional to the enzyme concentration providing there is an excess of the substrate molecule.
If substrate concentration is a limiting factor then there will be less collisions as the substrate molecules are used up. Thus enzyme activity will decrease.
When the graph plateaus there are no substrate molecules left to combine with.
How does substrate concentration affect the rate of enzyme controlled reactions?
Initially there are too few substrate molecules to collide with the available enzymes.
When there are equal amounts of substrates and enzymes the rate of reaction increases as all enzymes are able to form enzyme substrate complexes.
The graph begins to plateau when all active sites are occupied.
What is a buffer?
A molecule that maintains a constant pH in a solution of diluted acid or alkaline.
What is an competitive inhibitor?
Molecules that are structurally similar to the substrate molecule bind to the active site preventing enzyme substrate complexes from forming.
How does increasing substrate concentration affect the competitive inhibitor?
It decreases the effect of the inhibitor as the enzyme is more likely to collide with the substrate molecule.
What is an non-competitive inhibitor?
Molecules that bind to the allosteric site of an enzyme and change the overall shape of the molecule including the active site.
How does increasing substrate concentration affect the non-competitive inhibitor?
No effect as enzyme substrate complexes are still unable to form.
What are immobilised enzymes?
Enzymes that have been fixed or bound to an inert matrix. Eg. Sodium alginate beads or cellulose microfibrils.
How are immbolised enzymes used in industries?
Immoblised on a membrane the substrate molecule must diffuse into the jelly matrix of the alginate beads to make direct contact.
How would you improve the use of immobilised enzymes?
Decrease flow rate so that there is more contact time between the enzyme and substrate molecule
Use smaller beads to increase the surface area allowing diffusion to take place quicker.
What are the advantages of immobilised enzymes?
Can be reused
Easily added and removed providing greater control over reaction
Can catalyse reactions over a wider pH range
Greater stability and so denatures at greater temperatures
Does not contaminate product.
