Mashrek International School

Effect of Different Concentrations of Enzyme on Enzyme Activity

What is the effect of changing the concentration of lipase enzyme on the enzyme activity in catalyzing lipids in whole milk?



Naim Al-Haj Ali
MYP Year 4B



Aim:
To investigate the effect of changing the concentration of lipase enzyme (2%, 4%, 6%, 8%, 10%) on the rate of enzyme activity in catalyzing lipids in whole milk (5cm3), by measuring the pH of the solution before and after adding the enzyme, keeping all the other variables controlled like the temperature, pH, and substrate concentration.

Scientific Background:
• Enzymes are biological catalysts, proteins that help in speeding up chemical reactions without being consumed. Enzymes have an active site to which one molecule called substrate can bind to. The active site makes each enzyme specific to one substrate; as the shape of the active site must complement the substrate’s to catalyze it. Enzymes catalyze chemical reactions by lowering their activation energy needed to start the reaction.
• Lipase is an enzyme that catalyzes the breakdown of lipids.
• Lipids are macromolecules, also called fats; they are made up of glycerol and fatty acids. Lipids can be found in dairy products, oil, and butter. Lipids can be used as long term energy storage and insulation; lipids are also a main part of the plasma membrane.
• Many factors can affect the rate of enzyme activity, like the enzyme concentration, substrate concentration, temperature, and pH.


Hypothesis:
If the enzyme lipase concentration increases, then the rate of enzyme activity would also increase; due to the fact that more enzyme molecules are present, thus more collisions with the substrate molecules happen in the same amount of time. Until a point (optimum point), where having a higher enzyme concentration would not increase the rate of enzyme activity, because the number of enzyme molecules become equal or more than the number of substrate molecules, thus having enzyme molecules with no substrate molecules to bind with. Also if the concentration of the enzyme decreases, then the rate of enzyme activity would also decrease.
The rate of enzyme activity increase when the concentration of enzyme increases due to the collision theory, where the more particles there is, the more effective collisions there is, thus increasing the rate of enzyme activity. 
Variables:
Independent:
The concentration of lipase enzyme (2%, 4%, 6%, 8%, 10%).
Dependant:
I will measure the pH of the solution after 5 minutes of adding the enzyme to the milk, using a pH meter.
Controlled:
• Temperature: an increase in temperature would make the particles

Materials: