2.5 Enzymes

Question 1

What are enzymes?

Answer 1

• they are catalysts
• proteins
• used in all cell metabolic reactions
• lower the activation energy needed for the reaction to occur
• have an active site to which the substrate binds
• very specific and can only catalyse one reaction as active site and substrate are chemically attracted to one another

Question 2

How do enzymes work?

Answer 2

• because of their shape (active site)
• it brings the reactive parts of molecules together - clicking them together or breaking them apart
• temporarily forming an enzyme-substrate complex
• change is induced in the shape of the enzyme molecule
• they are unchanged in this reaction and hence are able to catalyse another reaction
• reactions can only occur if the substrate are in liquid forms and in random motion they collide with one another

Question 3

Denaturation of Enzymes

Answer 3

denaturation is a structural change in a protein
usually permanent
heat and pH are normally what makes enzymes denature

Question 4

How does temperature affect enzymes?

Answer 4

• at low temp reaction is slow due to few collisions
• as temp increases the rate of reaction increases up until a point (optimum temp)
• the optimum temp of an enzyme depends on enzymes natural environment
• then action is slowed as the protein denatures
• active site of enzyme is altered and can no longer fit the substrate

graph: fast rise then peak then very quick fall, not symmetrical

Question 5

How does pH affect enzymes?

Answer 5

• enzymes catalyse reactions at a specific pH
• the optimum pH is specific for enzymes

graph: very steep rise then quickish drop, range is not very big, (skinnier than temp graph)

Question 6

How does enzyme concentration affect enzymes?

Answer 6

• as enzyme conc increases so does rate of reaction

- graph is linear, relationship is proportional

Question 7

How does substrate concentration affect enzymes?

Answer 7

• initially increasing substrate conc increases the rate of reaction
• eventually, it reaches a conc where enzymes can’t bind any more substrate, maximum reaction rate

graph: steady increase, levels off

Question 8

What are co-factors/co-enzymes?

Answer 8

the activity of some enzymes requires co-factors
- these may include metal ions, vitamins, minerals and organic chemicals that assist enzymes during the catalysis of a reaction

Question 9

How are enzymes used in industry?

Answer 9

• production of items such as juice and washing powder
• enzymes are usually immobilised by attachment to another material (so that their movement is restricted and they can be separated from the product so they can be reused)