Lab Topic: Enzymes
Bring your Symbiosis Lab Manual to Lab
I Specific Objectives of this Lab: After completing
this lab a student should be able to:
1 Define "enzyme" and write a sentence
describing how enzymes function in cells.
2 Write a paragraph contrasting the way
competitive and noncompetitive inhibitors work.
3 Write paragraphs describing the effects of
pH and temperature on enzymatic activity.
4 Write paragraphs describing the effects of
varying enzyme and substrate concentration
on enzyme activity.
5 Write an appropriate hypothesis and
prediction when given a scientific question.
6 Draw graphs of scientific data and explain them.
7 Write a definition for enzyme, substrate,
catalyst, cofactor, coenzyme, competitive
and noncompetitive inhibition, dependent variable,
independent variable, control
II Introduction
A Enzymes
1 see lecture Energy and Metabolism
as it relates to enzymes
B Information specific to Lab Topic: Enzymes
in Symbiosis Lab Manual
1 study two enzymes
a catechol oxidase
-found in most plant cells
-structure of catechol oxidase (Jmol)
-has Cu atoms as cofactors at its active site
-reaction catalyzed by enzyme
-phenylthiourea (PTU) is a specific inhibitor
-PTU binds to the Cu atoms
-measuring catechol oxidase activity
-measure the increase in product
(benzoquinone)
-initially, no benzoquinone (substrate only)
(substrate = catechol (colorless))
-enzyme binds its substrate (catechol)
-enzyme catalyzes production of
product = benzoquinone (yellow)
-benzoquinone is yellow then dark brown,
easy to measure
-follow reaction by observing the
appearence of yellow/brown product
-could measure catechol disappearence,
but catechol is not colored,
harder to measure
b amylase
-see structure of human salivary amylase (gif) (Jmol)
-amylose is another name for starch
-hence, amylase is an enzyme that
hydrolyzes amylose (starch)
-starch hydrolysis reaction
-measuring amylase activity
-amylose (starch) can be made visible by
adding iodine (I2)
-amylose + (I2KI) = reacts to yield
a black color
-maltose (colorless) does not
react with (I2KI)
-measure decrease of substrate
(amylose (black)) to measure
amylase activity
c in today's lab we will study the
-activity of catechol oxidase
-mode of inhibition of phenylthiourea
on catechol oxidase activitiy
-effects of pH on amylase activity
-effects of temperature on amylase activity
-the effects of enzyme concentration
d we will also review the
process of science
-identify general questions
-come up with hypotheses
-come up with specific predictions
-analyze results
-draw conclusions
e Note the Specific Assignments
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