enzymes tracking. Flashcards
Describe the difference between intracellular and extracellular enzymes. Give an example of both.
Intracellular work inside cells
For example catalase
Extra cellular enzymes work out of cells
For example amylase
State the type of molecule that all enzymes are.
Globular proteins.
Explain why enzymes work as catalysts.
Enzymes lower the activation energy of the reaction.
It does this by holding the substrate molecule(s) in the active site
This either reduces any repulsion between the substrate molecules
Or puts strain on the bonds of the molecule
This increases the rate of reaction
Describe the lock and key model of enzyme action.
Each enzyme has a specific substrate
That has a complementary shape to the active site
This forms an enzyme substrate complex
The substrate is converted into products
To form an enzyme product complex
The products leave the active site because it does not have a complementary shape
Describe the induced fit model of enzyme action.
The substrate binds to the active site
The enzyme changes shape slightly
To fit the substrate more closely
State the four factors that can affect the rate of enzyme reaction.
Temperature
pH
Enzyme concentration
Substrate concentration
Explain why enzymes have a low rate of reaction at temperatures lower than the optimum.
The enzyme and substrate molecules have low kinetic energy
Therefore they move slowly
There are fewer successful collisions between the enzyme and substrate molecules
Explain what happens to enzymes at temperatures above the optimum.
The enzymes denature
This is because the extra kinetic energy makes the enzyme molecule vibrate more
This can break some of the bonds holding the enzyme in its tertiary structure
The active site changes shape
The substrate can longer fit into the active site.
Describe what is meant by the temperature coefficient Q10.
How much the rate of reaction changes, with a temperature increase of 10°C
For most enzyme controlled reactions Q10 = 2
But only up to the optimum temperature
Explain why enzymes are denatured in extremes of pH.
Acidic solutions contain hydrogen ions H+
Alkali solutions contain hydroxide ions OH-
These ions interfere with the ionic and hydrogen bonds holding the tertiary structure in place
Therefore the active site changes shape
The active site is not complementary to the substrate
Explain a graph where rate of reaction increases as substrate concentration increases, but eventually levels off.
The rate of reaction increases because the substrate concentration increases.
There are more substrate molecules
and therefore a higher chance of a substrate molecule colliding with an enzyme
to form an enzyme substrate complex.
When the rate reaction becomes constant the enzyme concentration is the limiting factor.
This is the Vmax.
Describe and explain the relationship between enzyme concentration and rate of reaction.
As enzyme concentration increase so does the rate of reaction.
There are more enzyme molecules
and therefore more chance of a collision between the enzyme and substrate
to form an enzyme substrate complex.
The rate of reaction will then become constant
as the substrate concentration becomes the limiting factor.
Describe the difference between a reversible and non-reversible enzyme inhibitor.
Reversible inhibitors form weak bonds with the enzyme
For example hydrogen or ionic
Therefore the inhibitor does not bind permanently
Irreversible inhibitors form strong bonds with the enzyme
For example covalent
Therefore they bind permanently
Describe how a competitive enzyme inhibitor works.
The inhibitor has a similar shape to the substrate
Therefore the inhibitor enters the active site and blocks it
Fewer enzyme substrate complexes can be formed
The rate of reaction decreases
Describe how a non-competitive inhibitor works.
The inhibitor binds to the enzyme
but not at the active site
It binds at an allosteric site.
The changes the tertiary structure of the enzyme
and therefore the shape of the active site.
Therefore the substrate can’t enter the active site.
The rate of reaction decreases.
State what is meant by product inhibition.
The product of a reaction inhibits the enzyme that catalyses the reaction
Describe how end product inhibition can regulate the rate of reactions in a metabolic pathway.
If the concentration of product is high
The enzyme catalysing the reaction will be inhibited
This will cause the concentration of product to fall
The enzyme will be less inhibited
The rate of reaction will increase.
Give an example of a cofactor and describe what it is.
An inorganic molecule or ion
They help the substrate to bind to the active site of the enzyme
The cofactor is not used up during the reaction
For example chloride ions are a cofactor for amylase
Give an example of a coenzyme and describe what it is.
A coenzyme is a cofactor that is an organic molecule
The coenzyme participates in the reaction
Normally by carrying chemical groups between different enzymes
For example vitamins
Give an example of a prosthetic group and describe what it is.
A cofactor that is permanently bound to the enzyme
For example Zn2+ ions are a cofactor for carbonic anhydrase
Explain what inactive precursors are and give an example.
An inactive form of an enzyme that needs to be activated to work
For example some protease enzymes are released as inactive precursors
This prevents them from damaging the cells they are produced in
