Factors affecting enzyme action Flashcards
What factors affect enzyme action?
Temperature
pH
Substrate concentration
Enzyme concentration
Inhibitors (competitive/non-competitive)
What happens at low temperatures to enzymes?
Rate of reaction is low
Enzyme and substrate molecules have low kinetic energy
What happens to enzymes when the temperature increases up to the optimum?
Increases rate of reaction
Kinetic energy of the enzyme and substrate molecules increases
Increases the chance of successful collisions
More enzyme-substrate complexes are formed
When is the rate of reaction at its highest in terms of temperature?
When optimum temperature is reached
What happens to enzymes when the temperature goes above the optimum?
Rate of reaction decreases
Molecules have more kinetic energy
Increasing vibrations begins to break hydrogen bonds, changing the tertiary structure of the enzyme
Alters shape of the active site so its no longer complementary to the substrate
Lowers the rate of reaction as enzyme-complexes cannot form
What happens to enzymes at very high temperatures?
Rate of reaction falls to zero
Enzymes are denatured
When the active site is permanently distorted by irreversible breaking of hydrogen bonds
This prevents the substrate from binding as it is no longer complementary to the active site
What do most enzymes have in terms of pH?
An optimum pH
Which the rate of reaction is at its maximum
What sort of range can enzymes only work within in terms of pH values?
Narrow range
What can small deviations from the optimum pH cause?
Reversible changes in enzyme structure resulting in inactivation
What can extreme deviations from the optimum pH cause?
Can permanently denature an enzyme
What may an extreme change in the pH alter?
Electrostatic charge on the side chains of the amino acids
If the active site has too many H+ ions (acidic) or OH- ions (alkali) the active site and substrate may both have the same charge and the enzyme will repel the substrate
Why might buffers be added to enzyme-controlled reactions?
To maintain a constant pH
What happens to the rate of reaction at a fixed enzyme concentration?
Rate of reaction will increase as substrate concentration increases
What is the limiting factor at low substrate concentration?
Substrate concentration
Enzyme molecules have only a few substrate molecules to collide with
What happens when more substrate is added?
More successful collisions
More enzyme active site become occupied
Eventually the rate of reaction reaches a maximum
Substrate molecules are in excess
Enzyme concentration becomes the limiting factor
