This preview shows page 1. Sign up to view the full content.
Unformatted text preview: s (of product) / unit time. There are
many ways to calculate v0. The approach we will use is
Absorbance vs. Time for Rxn. X
based on the following:
Begin by plotting absorbance vs. time for each
trial in a manner similar to that shown at right. (Note:
when analyzing your data, you should plot all of the
traces for a given experiment on the same graph.) @ 410 nm 2 1.5 Z 1 Once this is done, you should see that each trace
exhibits a relatively long segment that falls in a straight
line (or very close to straight). For the graph above, this
linear segment falls between points “Y” and “Z”. The
slope ( A/ t) of this portion of the trace is related to
(but not equal to) the v0 for Rxn. X. The reason that this slope does not represent the initial velocity of
the reaction is that A/ t is a meaningless expression since absorbance is a unitless value. A step in
the right direction is to use Beer’s law to convert the absorbances to concentrations of product. This
conversion gives the change in concentration of product made vs. the change in time. However, this
value does not tell us much more than A/ t. So, it is necessary to change the concentration values to
moles by multiplying the concentrations by the reaction volume used in the experiments: moles/liter
(concentration) x .005 liter (reaction volume) = moles of product. Once this is done, you end up with
moles/ t which is an expression of initial velocity.
QUESTION: If the product of Rxn. X is p - nitrophenol (E410 = 1.83 x 104 liters per mole x
centimeter), what is the v0 of Rxn. X as plotted above?
(ANSWER: 2.9 x 10-9 moles / sec.) Biology 05LA – Fall Quarter 2012 Lab 5 – page 4 Learning Goals/Intended Outcomes
1. Be able to define the following terms: enzyme, substrate, product, enzyme-substrate complex, and
2. Be able to use the above terms to describe the catalytic cycle of an enzyme.
3. Be able to define the term chromogenic substrate.
4. Be able to explain the experimental strategy for our investigations of the activity of bovine alkaline
phosphatase. Your response should include:
a. an explanation of why a chromogenic substrate and a spectrophotometer were used.
b. a definition of the term initial velocity (v0).
c. an annotated outline of the procedure used for converting the measured rates of color
change in the reaction tubes to the v0’s for these reactions.
5. Be able to explain the necessity of the “0.0 M substrate” trial in the [substrate] experiment.
6. Be able to present and explain the supporting facts that you used to support your hypotheses for the
two studies that you performed.
7. Be able to interpret the data presented in the following graphs by filling in the blanks in the table
below with the number of the plot that is the best match for the listed description / explanation of
the data. You must be able to explain your choice.
2 5. 1 1 Time Time 2 6. Abs. Abs. Abs. 2 3. 1 Time Time
4. 2 Abs. 1 1 2 2. Abs. 1. Abs. 2 1 Time Description / Explanation
The plot that depicts the slowest reaction rate
The plot that depicts data for which a v0 cannot be validly calculated.
The plot that shows the result of an experiment where the enzyme was denatured.
The plot that depicts the fastest reaction rate.
The plot that shows the result of an experiment where the substrate was
contaminated with enzyme prior to the start of the experiment.
The plot that shows the result of an experiment where the substrate was completely
converted to product during the experiment. Time Plot # Biology 05LA – Fall Qtr. 2012 Lab 6 – page 1 LAB #6: FERMENTATION AND RESPIRATION
All living organisms must continuously expend energy to maintain themselves and drive
energy-requiring life processes. This energy is ultimately derived from the sun via photosynthesis.
Because not all organisms are photosynthetic and the sun does not always shine, organisms need
alternative sources of energy. Plants provide this energy in the form of organic molecules that contain
large amounts of chemical potential energy. These molecules (e.g. sugars) are relatively stable and can
be stored or transported. This energy is extracted by a stepwise, enzymatically-mediated oxidation of
these molecules that results in the production of another energy-storing molecule, adenosine
triphosphate (ATP). When the terminal phosphate of ATP is split off, the ATP is converted to ADP
(adenosine diphosphate) and considerable energy is made available for “cellular work”. The ADP is
then available for the regeneration of more ATP. Shown below are balanced summary equations for
two classes of metabolism that provide most of the ATP that cells use.
C6H12O6 (glucose) + 2 ADP + 2 Pi 2 CH3CH2OH (ethanol) + 2 CO2+ 2 ATP + heat
Alcoholic Fermentation C6H12O6 + 6 O2 + 32 ADP + 32 Pi
6 CO2+ 6 H2O + 32 ATP + heat
The experiments that you will perform in this exercise are made possible by two features
related to the above equations. The first is that gaseous reactants and/or products are characteristic of
both metabolic processes. The second is that it is relatively easy to determine number of moles of a g...
View Full Document
This note was uploaded on 08/27/2013 for the course BIO BIOL05LA taught by Professor Abbottl during the Fall '12 term at UC Riverside.
- Fall '12