FREE ESSAY ON PROTEIN ENZYME LAB

PROTEIN ENZYME LAB

Biology Lab Report
Title: Examining Some Properties of the Enzyme -amylase
Introduction: 
In this experiment a deeper meaning in the catalysts of reactions is studied. Catalysts
accelerate chemical reactions without permanently changing the reaction. Enzymes,
catalysts in biochemical reactions, are globular proteins which lower the activation
energy needed to begin a reaction and therefore increase the rate at which efficient
reactions can occur. Proteins (henceforth enzymes) are complex molecules made of amino
acids in polypeptide chains held together by peptide bonds. The structure of proteins is
broken up into primary, secondary, tertiary, and quaternary structures which create
complex structures which can be separated and identified by paper chromatography, or more
importantly spectrophotometry can determine the concentration of proteins in an aqueous
solution. 
Spectrophotometry is a quantitative analysis used to determine the amount or
concentration of a substance ( -amylase) from its ability to absorb radiant energy. The
substance is usually colored and radiant energy used is visible light, which passes
through the solution and is either absorbed or transmitted. The spectrophotometer
measures is an instrument (used here in our experiment) which electronically measures the
amount of transmitted and absorbed light, and can determine concentration and wavelength.
The concentration of a solution can be determined because the amount of light absorbed by
a solution is dependent on its concentration. A relationship between absorbance and
concentration can be made by the Beer-Lambert Law which states absorbance is equal to a
molar extinction coefficient times the concentration of the solution times the length of
the light path through the solution. The absorbances over a range of known concentrations
of the substance are measured at lambda max, the wavelength which shows maximal
absorbency. For the purpose of our lab, wavelength will not need to be found, but merely
the spectrophotometer must be set to 560 nm. 
The reacting molecule in an enzymatic reaction is called a substrate. The purpose of this
lab is to determine the maximum velocity and substrate concentration for the reaction of
-amylase and starch. The substrate (starch) and the enzyme ( - amylase) come together for
a short time and then break down to yield the products and enzyme. Once the enzyme
configuration is altered in the reaction it is useless and becomes decomposed in the
normal course of cellular metabolism. The rate of the enzymatic reaction, needed for
figures three and four, is set by the rate at which the enzyme-substrate complex forms
and then decomposes to form the product. The amount of time it takes the enzyme to effect
the substrate and the frequency at which the complex (enzyme-substrate) forms. The
frequency depends greatly on the concentration of the substrate. As the reaction
proceeds, and starch is turned into the product by the enzyme the chances of the enzyme
encountering a starch molecule becomes less and so the reaction rate decreases. Most
starch is converted at the initial stage of the reaction and therefore the maximum
reaction rate is highest at this stage in the reaction. From a resulting curve from of
the enzymatic reaction, showing disappearance of substrate over time, the maximum
velocity at which that particular reaction occurs and the concentration of the substrate
at which Vmax/2 occurs can be determined.
Although substrate concentration is important in determining the rate of the reaction, it
is not the only factor. Certain physical environment factors of the enzyme such as
temperature and pH can affect the reacting molecules and catalytic activity of the
enzyme. We intend to use these factors in determining the optimal efficiency for
-amylase, as an enzyme works optimally at a particular temperature and pH. We can find
these optimal levels more easily by graphing the reaction rate verse temperature, and
verses pH (figures three and four). We can also check the absorbance over time for
difference temperatures and pH's in order to help us procure the reaction rates (figures
one and two). Heat in any system (def.) tends to increase molecular motion, and therefore
increases the chances of the enzyme encountering a substrate. Therefore, the reaction
rate is clearly increasing as enzyme activity increases, and vice versa. However great
high temperatures may seem, there is a limit. At really high temperatures the shape of
tertiary structure of the protein can be changed, and thus the enzyme is not nearly as
effective, and the reaction rate shall slow down. The efficiency of enzymes can be
graphed in a bell or spike shape. The optimal level of enzyme efficiency is important in
not only simple experiments such as this, but in animal/human body upkeep and simple
internal systems such as digestion. So, thermoregulation of temperature in a system or
body is important in function of life.
pH is the logarithm of the reciprocal of the hydrogen ion concentration of an
environment. The pH of the system can affect the structure of some enzymes. A pH of 7.0
is neutral, anything greater is base, anything less is acid. A pH differentiating from
optimum the hydrogen bonds in the tertiary structure of the protein (enzyme) are altered,
and again the enzyme can not function as well as before and the velocity of the reaction
is decreased.