Level 7 IA (22/25 points) conducted on topic 2.5 (enzymes). The IA explored what affect does Enzyme Trypsin has on protein Casein which is contained in milk. In addition to that, the IA explores how inhibitor ethanol affects the rate of the reaction.
Research Question
How does increasing the concentration of ethanol (5%, 20%, 40%, 60%, 80%) affect the rate of hydrolysis
of the protein casein in Bon taurus milk by 2% of the enzyme Trypsin, measured by absorbance of green
light by a colorimeter set at 565nm (±0.001nm)?
Background Information
Ever since I was a little child, my parents always told me that if I drink milk I will grow taller and
stronger. However, as I grew older and went to school, where in science classes we conducted research
investigation and experiments, I found out that what my parents were telling me was false and considered
myths. In addition to that, a lot of my friends are lactose-intolerant, and some are even allergic to dairy. This
made me question what other health implication milk might have.
An enzyme is a protein which acts as a biological catalyst by speeding up the rate of a chemical
reaction. (Cornell) Enzymes are proteins that function as the biological catalysts by increasing the rate of
chemical reactions in the body (a.k.a. metabolic reactions). (Cornell) The active site is a binding region for
the substrate that complements the enzyme in shape and chemical properties. Enzymes catalyze substrates at
the active site. During the catalysis of the substrate, an enzyme-product substrate is created where the
product then dissociates. (Cornell)
Trypsin is an enzyme that is important for the digestion of proteins and regulation of the trypsin
levels in the body. (Worthington) Since trypsin is a protein itself, it degrades proteins by “itself digestion”
which in other words is called autolysis. It is produced in the pancreas and is inactive pro-enzyme called
trypsinogen. Trypsinogen is secreted in the small intestine where it then gets activated for digestion and
turns into trypsin. Humans are able to generate enough enzymes, including trypsin, which helps to break
down food and proteins into amino acids that the body then uses for healthy tissue growth, maintenance and
repair. (Worthington)
Casein is a protein that is found in milk. It is found in cow’s milk and any other dairy products made
from cow’s milk. (Bond) It makes up the majority of the proteins found in dairy products and supposedly
has hidden risk for health complication. (Bond) Casein has a thick consistency and forms a strong mucus
substance therefore, it can cause problems with a respiratory system which will lead to clotting and
irritation. Due to the clogging, the body may experience high fevers, asthma, colds and other common
allergies to dairy. (McClees) In addition to that, studies such as one conducted by Dr. Collin Campbell
called “The China Study” where it was investigated the relationship between nutrition and diseases such as
diabetes, cancer and other heart diseases in rural countries in China. (Campbell) He discovered that there is a
link between the animal protein ingested into the body and the
occurrence of cancer and since the dairy is mostly composed of
casein, he concluded that it speeds up spreading of cancer in all
the stages. (Campbell) Therefore, trypsin is important to the body
as it hydrolyses casein molecules into peptides and amino acids
which can be easily absorbed by human bodies rather than casein
untreated casein, which prevents clogging in the respiratory
system.
However, enzyme inhibitors can be the cause of the decrease in
rate of hydrolysis. Ethanol is a competitive inhibitor of trypsin,
which means that it directly competes with substrates for the
Fig. 1: (Cornell)
attachment to the active site. It happens due to the structures of inhibitors and substrate molecules being
chemically and structurally similar therefore capable of binding to an active site. Therefore, as seen on the
graph if the substrate concentration is increased, it will outnumber the inhibitor molecules and the reaction
will increase. However, if the number of inhibitor molecules will increase, then the substrate molecules will
be outnumbered which will cause the reaction rate to decrease. (John)
In my experiment, I will investigate if increasing ethanol solution which acts as a competitive
inhibitor for enzyme Trypsin will affect the hydrolysis rate of casein in Bon taurus milk. I will increase the
concentrations of ethanol to see if higher concentrations will decrease the reaction rate more efficiently.
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