Enzymes

Question 1

Explain why an enzyme is specific to its substrate.

Answer 1

Enzymes have a specific 3D shape with an active site that is complementary to the shape of the substrate, enabling successful binding. Substrates that are not complementary to the enzyme’s active site will not be able to bind.

Question 2

Define activation energy.

Answer 2

The initial input of energy required for a chemical reaction to take place.

Question 3

Explain how enzymes increase the speed of a chemical reaction.

Answer 3

Lower the activation energy by placing stress on the bonds of the substrate, meaning less energy is required to break the bonds.

Question 4

State three factors that may affect enzyme activity. Explain how each factor affects enzyme activity.

Answer 4

Temperature:
* Too low; molecules have less kinetic energy (do not move as quickly), resulting in less successful collisions between reactants and enzymes per unit time.
* Too high: thermal energy causes enzyme to denature (irreversible change in shape of enzyme) – thus active site is no longer complementary to substrate, preventing successful binding.
pH:
* Excess H+ or OH- in environment of enzyme can denature the enzyme - disrupt the charges of amino acids, altering the bonding and therefore structure of the enzyme. (no longer complementary to substrate).

Presence of Chemical Inhibitors
* Competitive: has a shape complementary to the shape of the active site, enabling it to bind. This prevents the substrate from binding to the active site.
* Non Competitive: binds to a site other than the active site, changing the shape of the active site so that it is no longer complementary to the substrate, preventing successful binding between substrate and active site.