enzymes

Question 1

enzyme

Answer 1

1. it is a protein
2. it functions as a biological catalyst
3. it speeds up chemical reactions
4. it remains chemically unchanged at the end of the reaction
5. it speeds up chemical reaction by lowering activation energy
6. enzymes are required in a minute/ small amount
7. enzymes are highly specific in action

Question 2

activation energy

Answer 2

energy needed to start a chemical reaction

Question 3

lock and key hypothesis

Answer 3

• an enzyme has an active site
• only substrate with 3-D shape complementary to that of the active site of the enzyme can fit into enzyme to form an enzyme substrate complex
  (enzyme is lock; substrate is key
• chemical reactions occurs and the substrate is converted into products
• the products then detach from the active site of enzymes. the enzyme remains chemically unchanged at the end of the reaction

Question 4

temperature

Answer 4

point A [low temperature]

• > enzymes are inactive at low temperatures - kinetic energy is low
• > effective collisions between enzymes and substrate are very low, leading to lower rate of reaction

point B [as temperature rises]

• > as temperature increases, enzyme activity increases
• > increase in kinetic energy increases the chances of effective collision between substrate and enzyme molecules
• > this increases the rate of formation of enzyme-substrate complex, hence rate of reaction increases.

point C [optimum temperature]

• > the optimum temperature is where the rate of reaction is the highest and enzyme is most active
• > the optimum temperature for different enzymes varies
• > for most enzymes, the optimum temperature is about 40-45°C

point D [beyond optimum temperature]

• > beyond the optimum temperature, the enzymes start to denature the enzyme activity decreases
• > high temperature breams the bond within the enzyme and changes the active site of its 3-D shape
• > the active site of enzyme loses its original shape.

point E [beyond optimum temperature]

• > the enzyme is now completely denatured
• > there is no enzymatic reaction.

Question 5

pH

Answer 5

• different enzyme have different optimum pHs, where it is most active
• extreme changes in pH (too high or too low) can denature the enzyme and cause it to lose its function

Question 6

limiting factor

Answer 6

any factor that directly affects the rate of reaction

• substrate concentration
• enzyme concentration

Question 7

denaturation

Answer 7

• the change in the 3-D shape of an enzyme or any protein.
• > affects the function of enzymes
• > caused by temperature or pH
• > when an enzyme is completely denatured, there is loss or change in the active site
• > the substrate can no longer fit into the enzyme’s active site, hence, no reaction can take place.