BIO 173 Quiz 1 UMich Study Guide
Exam and Actual Answers 2025-2026
Set.
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
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
, 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
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.
***
Exam and Actual Answers 2025-2026
Set.
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
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
, 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
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.
***
