BIO 173 Quiz 1 UMich Actual Exam/ 114 Q&A/ . Terms like:
Enzyme - Answer: A protein that catalyzes (speeds up) biological reactions
Active site - Answer: An area on an enzyme where the substrate binds during a reaction; The part of an enzyme where the chemical reaction occurs.
Substrate -...
BIO 173 Quiz 1 UMich Actual Exam/ 114 Q&A/
2024-2025
Enzyme - Answer: A protein that catalyzes (speeds up) biological reactions
Active site - Answer: An area on an enzyme where the substrate binds during a reaction; The
part of an enzyme where the chemical reaction occurs.
Substrate - Answer: The reactant of an enzyme-catalyzed reaction
Product - Answer: A substance produced in a chemical reaction
Vmax - Answer: The maximum rate of reaction, when virtually all enzyme active sites are filled
km - Answer: Substrate concentration at 1/2 Vmax (demonstrates the affinity an enzyme has for
a substrate). Will vary with temp, pH, and inhibitors. The lower the Km the more likely an
enzyme is operating at Vmax
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,Competitive inhibitor - Answer: A substance that reduces the activity of an enzyme by binding
to the enzyme's active site in place of the substrate. A competitive inhibitor's structure mimics
that of the enzyme's substrate.
Denaturation - Answer: A process in which a protein unravels, losing its specific structure and
hence function; can be caused by changes in pH or salt concentration or by high temperature
Denaturing agents - Answer: High temperatures or strong acids cause untwisting and
disorganization of the protein. Common factors that affect protein conformation are
temperature, pH, and the ionic composition of the solution
Non-competitive inhibitor - Answer: A substance that reduces the activity of an enzyme by
binding to a location remote from the active site, changing its conformation so that it no longer
binds to the substrate
Catalyst - Answer: Something that causes or accelerates a chemical reaction without being
affected itself.
Reaction Rate - Answer: The rate at which reactants change into products over time. For our
experiments, rate can be found by absorbance over time
Spectrophotometer - Answer: An instrument that measures the proportions of light of different
wavelengths absorbed and transmitted by a pigment solution. Used to measure the color of the
solutions in the experiments because the color change indicates the concentration of the
quinones and therefore the rate the reaction was occurring
Cofactor - Answer: Organic molecules or metal ions attached to the active site; extra substances
that are necessary for the reaction catalyzed by the enzyme
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, Logarithmic Graph - Answer: A logarithmic graph depicts decreasing returns. In a
Vmax/substrate concentration graph, as substrate concentration increases, the velocity
continues to increase by a smaller amount until the velocity increase is negligible. This velocity
"halt" is Vmax.
Absorbance - Answer: The amount of light absorbed by a sample. Used to measure reaction
rate, found by spectrophotometer
Catechol - Answer: The substrate used in the experiment, meant to react with PPO to produce
benzoquinone
PPO (polyphenol oxidase) - Answer: -The enzyme we used in the experiment, found in plants
and animals.
- an enzyme found in potatoes (and others), which may protect plants against predators
-converts catechol to orthoquinone
-orthoquinone breaks down into a series of other products, which happen to be colored
red/brown.
-the appearance of color suggests a way to measure reaction rate- spectrophotometry
-the amount of light absorbed is proportional to the amount of product present
Benzoquinone - Answer: Byproduct of PPO reaction; appears to be broadly toxic to a variety of
microbes and insects (protects the plant/fruit); turns brown/orange color
Percent inhibition - Answer: Percent drop in enzyme activity in the presence of the inhibitor.
***
Cellular Homogenization (in the centrifuge) - Answer: By homogenizing the potato in the
centrifuge we are able to release and extract the PPO enzyme, used as the enzyme in our
experiment
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