Practical: The Effect of the Enzyme Catalase from Chicken Livers on Hydrogen Peroxide
MEMO
PART A
1. Measured correct volume√.
(1)
2. The test for oxygen is putting a glowing splint into the gas that is being tested√. (1)
3. The glowing splint glows brightly√ and a flame is produced√
(2)
4. Yes catalase did speed up the reaction√
(1)
TOTAL PART A: 5 MARKS
PART B
1.
a. Measured correct volume√
(1)
b. Measured correct volume√
(1)
2. Measuring cylinder 1 had the greatest volume of bubbles that rose up ‘x ml’√
whereas measuring cylinder 2 rose by ‘y ml’√ and measuring cylinder by ‘z ml’√. (3)
3. At high temperatures, the rate of reaction decreases/almost stops completely√. This
is seen by the lack of O2 that is produced in the form of bubbles√. At cold
temperatures the rate of reaction is much slower√ as the O2 produced is not as great
as the room temperature experiment√. It seems that the optimum temperature for
chicken liver catalase out of these 3 experiments is room temperature√.
(5)
4. Volume of Hydrogen peroxide must be the same in all 3 experiments√
Mass of liver must be equal for all 3 experiments√
All three experiments must be done under the same time frame√
Concentration of hydrogen peroxide must be the same√
ANY OTHER 3 FIXED VARIABLES
(3)
5.
a. Temperature of the liver√
(1)
b. Volume of the bubbles that rise in the measuring cylinder√
(1)
6. If chicken liver catalase is at room temperature√ and placed into hydrogen peroxide,
it will produce a greater volume of oxygen bubbles√ than ice cold chicken liver or
boiled chicken liver.
√ MARK FOR WRITING HYPOTHESIS IN A STATEMENT.
7. Chicken liver catalase placed into hydrogen peroxide, produces the greatest volume
of oxygen bubbles√ when it is at room temperature√ compared to when it is ice cold
or boiled for 4 minutes. This shows that speed of the reaction is greater when
catalase is at room temperature.
(2)
TOTAL PART B: 15 MARKS
1
PART C
The reaction is a simple degradation/breakdown reaction in which hydrogen peroxide is
broken down into water and oxygen.√
We measured the reaction rate by the height/volume of oxygen bubbles that rose up in the
measuring cylinder√. It is safe to assume that the higher and quicker the bubbles rise will
indicate the speed of the reaction√.
This method is accurate, however it could be made more accurate by replicating the
experiment many times, thus getting a reliable average as a result√.
ANY OTHER LOGICAL REASONS SHOULD BE CONSIDERED.
(4)
Temperature and pH both affect the rate of reaction, as all enzymes have an optimal
temperature and pH at which they function√.
Enzymes denature at extreme pH and high temperatures√. Denaturation occurs when an
enzymes structure is irreversibly altered, so it stops functioning as it is supposed to√.
Low temperatures usually slow down the rate of reaction of enzymes and as the
temperatures increase to optimum, the rate or reaction increases√.
(4)
The importance of regulating temperature in living organisms√√.
The dangers of having a high fever√√.
Control of pH and temperature in the brewing process√√.
ANY EXAMPLE OF ENZYMES ACTION IN THE REAL WORLD.
TOTAL PART C: 10 MARKS
2
(2)