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Unformatted text preview: the lab notebook, but will not be graded. These items need to be prepared separately for each
1) Results. Begin by preparing the required graphs (if any) and then doing the required calculations.
Next prepare a simple table of your processed data (e.g. the different rates for the different
experimental conditions). Once the table is prepared, you then need to provide a brief statement
describing what the table shows. Do not make interpretations of your results at this time.
2) Discussion. For each question you need to do the following. First, briefly and clearly state how
well your predictions and results matched (be sure to mention the data that supports your claim).
In the case of a good match, conclude with a simple declarative statement of what was learned this should be expressed in the terms of your hypothesis. In the case of a poor match, describe
what you think went wrong and propose the specific changes that you think would improve your
results were you to perform the experiment again. These changes may be to the manner in which
you performed the experiment or to your original hypotheses.
*** Biology 05LA – Fall Quarter 2012 Lab 4 – page 6 The questions that will be addressed by the experimental labs this quarter are listed below or within the
relevant lab exercise.
The Enzyme Lab.
1) How will increasing substrate concentration affect the rate (v0) of an enzymatic reaction if the
enzyme concentration is held constant for the different trials?
2) How will altering pH affect the rate (v0) an enzymatic reaction?
The Fermentation and Respiration Lab – these will be presented with the lab exercise.
Learning Goals/Desired Outcomes
1) Be able to define and differentiate between the following pairs of terms:
a) inductive reasoning – deductive reasoning.
b) hypothesis – prediction. (an “educated guess” will not be considered as an adequate definition
of a hypothesis!)
c) experimental protocol – experimental strategy.
2) Be able to explain why gaining a thorough knowledge of the known facts related to a particular
question is a vital prerequisite to proposing a hypothesis for that question. Biology 05LA – Fall Quarter 2012 Lab 5 – page 1 LAB #5: ENZYMES
Enzymes are organic catalysts that participate in the chemical conversion of one organic
molecule to another. The molecule that is acted upon by an enzyme is known as its substrate and the
molecule that is formed by the reaction is called its product. Enzymes participate in these reactions
without being chemically changed as they are completed. Thus, one molecule of an enzyme could
theoretically catalyze many conversions of substrate to product. This recycling of enzyme in multiple
conversions of substrate to product is referred to as the catalytic cycle of an enzyme. It is described in
the box to the right.
When enzymes were first discovered, they were
given a wide variety of names. For example, the enzyme
that initiates the digestion of starch in the mouth, salivary
The catalytic cycle of an enzyme occurs in 3 steps.
amylase, was called ptyalin. Currently, enzymes are
The enzyme and substrate bind to form an enzymenamed systematically by what they do. The ending "ase"
substrate complex . While bound to the enzyme, the
identifies a substance as an enzyme. This ending is
substrate is converted to product resulting in an
preceded by a stem which indicates a specific substrate,
enzyme-product complex. The product is then released
and the enzyme if free to bind another substrate molecule.
the general nature of the substrate, or the type of action
catalyzed by the enzyme. For example, succinic
dehydrogenase removes two atoms of hydrogen from succinic acid, while hydrolases insert a molecule
of water across a bond and thereby hydrolyze a compound.
Most enzymes are proteins and are sensitive to environmental conditions. Enzymes, like most
proteins, can be irreversibly damaged or denatured by high temperatures or pH extremes. There are a
number of fascinating exceptions to these general rules: enzymes whose critical component is not
protein, enzymes from organisms that thrive in super-heated ocean volcanic vents, and enzymes that
operate quite well at very acidic or alkaline conditions normally viewed as deadly for all life. All
enzymes, even the unusual ones, have conditions of temperature, pH, and concentrations of enzyme
and substrates that promote their most efficient activity.
In today's exercises, we will examine the activity of bovine intestinal alkaline phosphatase
when exposed to variations in two of the above parameters. This enzyme normally operates in the
intestines of cattle, away from the acidic stomachs (cattle have more than one), breaking down a
variety of phosphorylated compounds found in their food. Alkaline phosphatase can hydrolyze the
artificial substrate p-nitrophenylphosphate, giving us a convenient way to make quantitative
measurements of its activity under different conditions. The basis for this convenien...
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- Fall '12