1.7-1.8 Enzyme Action & factors affecting it Flashcards
What is the definition of a catalyst
A catalyst can alter the rate of a chemical reaction without undergoing permenant changes, therefore they can be used repeatedly and therefore only effective in small amounts
What is meant by the induced fit model of enzyme action
This model proposes that the active site forms as the enzyme and substrate interact. A change in the environment leads to a change in the enzyme that forms the functional active site.
The enzyme is flexible it is like a glove that has a general shape but moulds itself to the user’s hand. In other words the enzyme’s active site is complementary, it changes slightly for the substrate.
As it changes it’s shape the enzyme puts s strain on the substrate molecule. The strain distorts a particular bond/s in the substrate and consequently lowers the activation energy needed to break the bond.
Explain why enzymes are effective in tiny quantities
They are not used up in the reaction and therefore can be used repeatedly
Why would changing one of the amino acids that make up the active site prevent the enzyme from functioning
This will cause the changes amino acid to not properly bind with the substrate and therefore stop it from positioning correctly to the active site
Explain why. Hanging certain amino acids that are not part of the active site also prevent the enzyme from functioning
The changed amino acid may be part of the amino acid which forms hydrogen bonds. Therefore this will disrupt the tertiary structure of the enzyme resulting in the change of the active site and so the substrate will no longer fit .
What is the difference between the lock and key model and the induced fit model?
The lock and key model of enzyme action suggests that the active site has a fixed shape like a “lock” and only one key, a specific substrate can successfully form a enzyme substrate complex. However, through observation other molecules could bind to enzymes at sites other than the active site therefore it suggested that the enzymes shape was altered by the binding molecule.
This goes against the idea that the active site is a rigid structure like a lock. Therefore the induced fit model is a better explanation of enzyme action in current observations
What conditions are needed for an enzyme to work
It has to come in physical contact with its substrate
Have an active site which fits the substrate
What is the effect of temp. On enzyme action
Rise in temp = increase of kinetic energy of molecules.
= rapid movement increase of collusion therefore more successful e-s complexes.
However rise in temp causes the hydrogen and other bonding to break in the enzyme molecule. This results in the change of shape of the enzyme including the active store. The substrate fits less easily therefore slowing the rate of reaction. This brings at 45c in humans
Complete denaturalising is at 60 when the enzyme is so disrupted that it stops working altogether. It is when the hydrogen bonds completely unravel
Effect of pH on enzyme action
A change in pH alters the charges on the amino acid that make up the active site of the enzyme. Substrate can no longer become attached to the active site and so the e-s complex cannot be formed
Can also cause the bonds maintaining the tertiary structure to break and unravel and the active site changes shape
The arrangement of the active site is partially determined by the hydrogen and ionic bond of the polypeptides. The change in H+ ions affects the bonding.
pH fluctuations inside organisms are usually small this means they are far more likely to reduce an enzymes activity than to denature
What does pH measure
It is the measurement of hydrogen ion concentration. Therefore optimum pH is the pH which it works the fastest
