Enzymes

Question 1

Define enzymes [6]

Answer 1

Biological catalysts[1] Made up of proteins[1]
Speed up chemical reaction via lowering activation energy required to start the reaction[1]
Remain chemically unchanged at the end of reaction thus can be reused[1]
Specific reactions with specific substrates, which is complementary in shape to active site of enzyme[1]
Sensitive to temperature and pH / can be denatured by extreme temp or pH[1]

Question 2

With reference to the lock and key hypothesis, describe enzymatic reaction. [4]

Answer 2

Enzyme is the lock, substrate is the key [1]
The three dimensional structure of the substrate must fit complementarily to the three dimensional structure of the active site on the enzyme [1]
To form enzyme-substrate complex for reaction to form products [1]
The enzyme remain chemically unchanged at the end of the reaction and can be reused.[1]

Question 3

With reference to the figure, explain how the inhibitor works in affecting enzymatic reaction. [3]

Answer 3

The inhibitor has complementary three dimensional shape to the active site of the enzyme and bind, thus blocking /occupy the active site. [1]
Substrate cannot bind to the active site to form enzyme-substrate complex. [1] The enzyme reaction is inhibited, no products form. [1]

Question 4

Describe and explain how enzyme functions are affected by temperature [4]

Answer 4

*note: must quote data if the Q involves graphical / table result analysis
Low temperature, enzyme activity is low as enzyme is inactive.
Temperature increases, enzyme activity increases due to kinetic energy increases, more effective collision between enzyme and substrate in forming more enzyme-substrate complex to form products
Optimum temperature, enzyme activity is the highest as enzyme is most active.
Beyond optimum temperature, enzyme activity drops. enzyme denatured due to change in three dimensional shape of active site.

Question 5

Describe and explain how enzyme functions are affected by pH [3]

Answer 5

pH too acidic, enzyme denatured due to change in three dimensional shape of active site. Enzyme activity decrease to zero, rate of reaction drops.
Optimum pH, enzyme is most active, enzyme activity is the highest
pH too alkaline, enzyme denatured due to change in three dimensional shape of active site. Enzyme activity decrease to zero, rate of reaction drops.

Question 6

Describe and explain how enzyme functions are affected by substrate concentration [3]

Answer 6

Increasing substrate concentration increases rate of enzymatic reaction. [1]
Max rate of reaction is reached when all enzymes’ active sites are saturated. [1] Reaction will only increase further if the concentration of enzymes is increased[1]

Question 7

Describe the importance of water in the human body [4]

Answer 7

Solvent in dissolving substances in the blood plasma
Maintain water potential in the blood plasma
Regulate body temperature by evaporation during sweating Site of chemical reactions in the cell cytoplasm.