Enzyme Action Flashcards
What is meant by the active site of an enzyme?
the active site is the part of the enzyme that the substrate molecules bind to.
What is meant by the activation energy of a reaction?
The minimum amount of energy that needs to be supplied to the chemicals to begin breaking reactant bonds and start a chemical reaction.
How does lowering the activation energy of the reaction increase the rate of reaction.
Lowering the activation energy reduces the temperature needed for the reaction to take place, which increases the rate of reaction.
e.g. dehydrogenase enzmye
En enzyme fits together with a substrate to form an enzyme substrate complex. This helps to lower the activation energy of the reaction. Give two ways the formation of the E-S complex achieves this.
- the E-S complex lowers the activation energy by holding the two molecules to be joined close to each other, reducing any repusion so that they will bond more easily.
OR
- the E-S complex lowers the activation energy by creating a strain on the bonds of a substrate as it fits into the active site allowing the bonds to break more easily.
Scientists used to explain enzyme action using the lock and key model, but this model is now considered insufficient. Explain why scientific models become insufficient. Name and describe the current model of the E-S complex.
Scientific models become insufficient because new evidence comes to light that invalidates them.
The current model of the E-S complex is the ‘induced fit’ model. This is where, as well as the substrate molecules having to be the right shape to fit the active site, enzymes must also change their shape slightly to accomodate the shape of the substrate.
Amylase catalyses the breakdown of starch but won’t catalyse the break down of other carbohydrates. Explain why.
amylase will only catalse the breakdown of starch as enzymes are highly specific. This means they only usually catalyse one reaction as only complementary substrate will fit into their active site.
What would happen to the activity of amylase if the tertiary structure was altered?
If the tertiary structure of amylase was altered then the site of its active site would change. This means amylase’s substrate, starch, will no longer fit the active site and the enzyme-substrate complex will not be formed. Therefore, amylase will not be able to break down starch.
What factors may change the tertiary structure of an enzyme?
The tertiary structure can be altered by pH or temperature. Changes in the amino acid sequence, by mutations in the gene that encodes the enzyme, can also change the tertiary stucture.
