CHAP 4 ENZYMES

Question 1

define ENZYMES

Answer 1

a biological catalyst that speed up chemical reactions without being altered by the reactions

Question 2

Describe mode of action of enzymes using LOCK & KEY HYPOTHESIS [4]

Answer 2

1) enzymes has a specific active site
2) the substrate has 3D-shape complementary to the active site so it can fit & bind to the active site of the enzyme , forming an enzyme-substrate complex
3) the reaction converts the substrate into product molecules which detach itself from the active site , leaving the enzyme free to bind with more substrates & catalyse the reaction
4) the enzyme remains unchanged & can be reused

Question 3

Describe the effects of temperature on the rate of enzyme-catalyses reaction [6]

Answer 3

1) At low temperature-> enzymes have a low rate of reaction
2) Substrate & Enzyme molecules have little kinetic energy -> frequency of collisions is low
3) As temperature increases, the rate of enzyme activity increases -> enzyme have more kinetic energy & collide more frequently -> rate of effective collisions is increased-> increase of rate of enzyme-substrate complex formation
4) Each enzyme has its optimum temperature, enzyme activity is highest here
5) As temperature increases beyond the optimum temperature , enzyme loses its shape -> no longer complimentary to the shape over substrate molecules
6) At extreme temperatures, enzymes are denatured -> Rate of reactions=0

Question 4

describe the effects of pH on the rate of enzyme-catalysed reactions [5]

Answer 4

1) enzyme activity is the highest at the optimum pH of the enzyme
2) as pH increases or decreases from the optimum, enzyme activity sharply decreases
3) extreme changes in pH loses active shape of active site & denatures the enzyme
4) Rate of reaction =0
5) optimum pH for each enzyme differs