Lactase Enzyme
Activity with Data
Analysis
Simulation at jondarkow.com
Pre-Lab
1. Define the following and explain how each relates to the
lactase chemical reaction.
➔ Enzyme
An enzyme is a globular protein that works as a catalyst, which means that it speeds up chemical
reactions. Lactase is an enzyme that converts lactose into glucose and galactose.
➔ Substrate
A substrate is the substance that enzymes convert into products. In the case of lactase, its substrate is
lactose.
➔ Active site
The active site is the specific region on the surface of the enzyme to which the substrate binds. The
shape and chemical properties of the active site and the substrate match, which allows the substrate to
bind but not others. This means that in the case of lactase, lactase’s only substrate is lactose, and the
breakdown of lactose can only be catalyzed by lactase.
➔ Rate of reaction
The velocity at which substrates are turned into products. The rate varies depending on factors such as
pH, temperature and substrate concentration, which means that an enzyme, for example lactase, will
have an optimal pH and temperature at which the rate of reaction will be the highest.
➔ Activation Energy
The activation energy is the energy required to start a reaction.The rate of reaction increases if the
activation energy decreases as less energy is needed to catalyse the reaction. Lactase uses energy to
convert lactose into glucose and galactose.
2. What is the chemical reaction that lactase catalyzes?
The breakdown of lactose into glucose and galactose.
, 3. Why would having the enzyme lactase as an adult be an evolutionary advantage? (think about this,
but we need to study some Evolution first….)
It would be an evolutionary advantage because of the fact that lactose is not used by cells for
metabolism to produce ATP unless it is broken down into glucose and galactose, which can be used to
produce ATP. Without lactase, we wouldn't be able to use lactose as a source of energy for cells.
According to Darwin’s “natural selection” theory, species that acquire adaptations favorable for their
environment will pass those adaptations to the offspring, which in this case would be the ability to
produce lactase enzymes (LAC gene in humans).
4. Explain how the structure of an enzyme relates to how well the function catalyzes chemical reactions.
The structure of an enzyme is important as it allows for the correct substrate to bind to the enzyme’s
active site. The shape of the active site matches the shape of the substrate, which means that if the
enzyme changes its structure, it won't be able to catalyse the reaction anymore.
Simulation Option 1: Temperature
1. Start with the initial lactose at 500 mg/dL and the pH at 7. Do not vary these parameters while testing
for temperature, they are environmental controls. The temperature is in degrees Celsius.
Be sure to show the instructor your method for calculating therate of reaction for the first 3
minutesbefore going on. The units should be mg/dL glucose per minute.
Vary the temperature by 20oC. Run each experiment 5 times (for reliability in the results.) Record the rate
of reaction in the table below. The rate of reaction should be in mg/dL of glucose per minute.
0oC 20oC 40oC 60oC 80oC
Trial 1 0 mg/dL per 73,6 mg/dL 74 mg/dL per 8,83 mg/dL 0 mg/dL per
minute per minute minute per minute minute
Trial 2 0 mg/dL per 49,3 mg/dL 64 mg/dL per 7,1 mg/dL per 0 mg/dL per
minute per minute minute minute minute
Trial 3 0 mg/dL per 59,7 mg/dL 53,3 mg/dL 7,03 mg/dL 0 mg/dL per
minute per minute per minute per minute minute
Trial 4 0 mg/dL per 61,3 mg/dL 72 mg/dL per 4,57 mg/dL 0 mg/dL per
minute per minute minute per minute minute
Trial 5 0 mg/dL per 47 mg/dL per 74,3 mg/dL 3,77 mg/dL 0 mg/dL per
minute minute per minute per minute minute
Mean 0 mg/dL per 58,18 mg/dL 67,52 mg/dL 6,26 mg/dL 0 mg/dL per
minute per minute per minute per minute minute
Activity with Data
Analysis
Simulation at jondarkow.com
Pre-Lab
1. Define the following and explain how each relates to the
lactase chemical reaction.
➔ Enzyme
An enzyme is a globular protein that works as a catalyst, which means that it speeds up chemical
reactions. Lactase is an enzyme that converts lactose into glucose and galactose.
➔ Substrate
A substrate is the substance that enzymes convert into products. In the case of lactase, its substrate is
lactose.
➔ Active site
The active site is the specific region on the surface of the enzyme to which the substrate binds. The
shape and chemical properties of the active site and the substrate match, which allows the substrate to
bind but not others. This means that in the case of lactase, lactase’s only substrate is lactose, and the
breakdown of lactose can only be catalyzed by lactase.
➔ Rate of reaction
The velocity at which substrates are turned into products. The rate varies depending on factors such as
pH, temperature and substrate concentration, which means that an enzyme, for example lactase, will
have an optimal pH and temperature at which the rate of reaction will be the highest.
➔ Activation Energy
The activation energy is the energy required to start a reaction.The rate of reaction increases if the
activation energy decreases as less energy is needed to catalyse the reaction. Lactase uses energy to
convert lactose into glucose and galactose.
2. What is the chemical reaction that lactase catalyzes?
The breakdown of lactose into glucose and galactose.
, 3. Why would having the enzyme lactase as an adult be an evolutionary advantage? (think about this,
but we need to study some Evolution first….)
It would be an evolutionary advantage because of the fact that lactose is not used by cells for
metabolism to produce ATP unless it is broken down into glucose and galactose, which can be used to
produce ATP. Without lactase, we wouldn't be able to use lactose as a source of energy for cells.
According to Darwin’s “natural selection” theory, species that acquire adaptations favorable for their
environment will pass those adaptations to the offspring, which in this case would be the ability to
produce lactase enzymes (LAC gene in humans).
4. Explain how the structure of an enzyme relates to how well the function catalyzes chemical reactions.
The structure of an enzyme is important as it allows for the correct substrate to bind to the enzyme’s
active site. The shape of the active site matches the shape of the substrate, which means that if the
enzyme changes its structure, it won't be able to catalyse the reaction anymore.
Simulation Option 1: Temperature
1. Start with the initial lactose at 500 mg/dL and the pH at 7. Do not vary these parameters while testing
for temperature, they are environmental controls. The temperature is in degrees Celsius.
Be sure to show the instructor your method for calculating therate of reaction for the first 3
minutesbefore going on. The units should be mg/dL glucose per minute.
Vary the temperature by 20oC. Run each experiment 5 times (for reliability in the results.) Record the rate
of reaction in the table below. The rate of reaction should be in mg/dL of glucose per minute.
0oC 20oC 40oC 60oC 80oC
Trial 1 0 mg/dL per 73,6 mg/dL 74 mg/dL per 8,83 mg/dL 0 mg/dL per
minute per minute minute per minute minute
Trial 2 0 mg/dL per 49,3 mg/dL 64 mg/dL per 7,1 mg/dL per 0 mg/dL per
minute per minute minute minute minute
Trial 3 0 mg/dL per 59,7 mg/dL 53,3 mg/dL 7,03 mg/dL 0 mg/dL per
minute per minute per minute per minute minute
Trial 4 0 mg/dL per 61,3 mg/dL 72 mg/dL per 4,57 mg/dL 0 mg/dL per
minute per minute minute per minute minute
Trial 5 0 mg/dL per 47 mg/dL per 74,3 mg/dL 3,77 mg/dL 0 mg/dL per
minute minute per minute per minute minute
Mean 0 mg/dL per 58,18 mg/dL 67,52 mg/dL 6,26 mg/dL 0 mg/dL per
minute per minute per minute per minute minute
