Remedial Assignment: Enzymes
Name: ________________
Your mission is to “save-as” to your own directory, complete the assigned
questions (while you avail yourself of the CD-Rom presentation) and then send me the
completed package via Email (rstevenson@papcs.com)
Of course, if you’d rather, do feel free to print the beast up and turn it in the oldfashioned way. As you might have guessed, I’d prefer the more “high-tech” option.
Enzymes
o The chemical reactions involved in cell functions (e.g., food molecules
taken into cells are broken down to provide the chemical constituents
needed to synthesize other molecules; enzymes facilitate the
breakdown and synthesis of molecules)
o Chemical reactions can be accelerated by catalysts (e.g., metallic
surfaces, enzymes)
Enzymes and Chemical Reactions
Enzymes
Please load the CyberEd Biology Course Title: Enzymes.
View Scenes # 1 – 7 and complete the exercise below.
Examine where enzymes are produced, and where and how they act.
Multimedia
Presentation
Scenes 1 – 3
1a.
What is a chemical reaction?
When molecules react with each other to produce different molecules, the process
is called a chemical reaction.
1b.
What is an enzyme, chemically, and what is its function in a living organism?
Enzymes are large molecules that facilitate chemical reactions inside and outside
cells at production rates necessary to sustain life.
1c.
Where are enzymes produced?
Enzymes are produced within the cells of an organism.
1d.
Explain the terms “enzyme-catalyzed reaction” and “substrate.”
involving an enzyme is called an enzyme-catalyzed reaction.
Scenes 4 –6
2.
Body Heat: this graphic shows
the effect of lowering the energy of
activation.
2a.
Define “energy of activation.”
Energy of activation: the specific
amount of heat energy required
for a chemical reaction to occur.
2b.
In the bottom graph, why can’t
the energy of activation be
reached simply by adding heat to
an organism, as at label a?
The organism dies when its body
temperature is raised too high for
too long.
2c.
In the top graph, what keeps the
energy of activation within an
organism’s heat energy survival
zone, as at label b?
Enzymes
Scene 7
3.
Explain how enzymes are named.
The suffix added to a prefix derived from the name or type of the substrate.
Scenes 1 – 7
4.
After hunting and eating a mouse at night, a rattlesnake rests on an asphalt road
still warm from the daytime sun. Explain this behavior in terms of what you have
learned about enzymes.
The snake is raising its body temperature so that enzymes can carry out digestion
of the mouse. Too much direct heat would kill the snake. (Some students may
know that reptiles need to seek out warmth in order to regulate their body
temperature.)Enzyme Structure and Substrate Interaction
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
View Scenes # 8 - 12 and complete the exercise below.
Learn about the molecular structure of enzymes.
Multimedia
Presentation
Scenes 8 – 9
1a.
Enzymes are what kind of molecule? How big are they, relative to other molecules?
Enzymes are protein molecules consisting of a great many atoms (macromolecules), and are
usually much larger than the substrates they catalyze.
1b.
Define “active site.”
The active site of an enzyme molecule is a pocket (groove, cleft or crevice)
shaped to fit only one or two types of substrate.
Scenes 10 – 12
2.
Different Strokes: these two sequences show two different models for enzyme and substrate
interaction.
2a.
What model is
represented by the
series that starts with
label a?
Lock and Key
2b.
What model is
represented by the
series that starts with
label e?
Induced Fit
2c.
Label b points out what
feature?
A lock and key active site
2d.
What is happening at label f?
An induced fit active site is changing shape.
2e.
What are the couplings at labels c and g?
Each is an enzyme-substrate complex.
2f.
What is portrayed at labels d and h?
The products, after the enzyme has broken bonds within the substrate molecules
2g.
Besides breaking substrate bonds, what else can enzymes do?
They can also create bonds between substrate molecules, combining
them into one.
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
Complete Interactive Lessons #1 – 2.
A review of enzyme structure and chemical interactions.
Interactive
Lesson
Enzyme Activity: Environmental Factors
Scene 13 1. The essential characteristic of catalysts is that they are not
consumed or changed by reactions; they only facilitate reactions. Describe how
is this true for enzymes.
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
View Scenes # 13 - 19 and complete the exercise below.
Learn how temperature, concentration, and pH affect enzyme activity.
Multimedia
Presentation
Enzymes can participate over and over in reactions, a single molecule catalyzing thousands of
reactions each second. Therefore, small concentrations of enzymes in cells are sufficient.
Scenes 14 – 17
2.
These tables compare how temperature and concentration affect enzyme activity. Complete the
tables.
2a.
Increasing the Temperature
At low values, the effect on enzyme activity:
Enzyme activity steadily increases as the
temperature rises.
2b.
Increasing the Concentration of Enzyme
At low values, the effect on enzyme activity:
Enzyme activity increases with additional
enzyme molecules
2c.
Increasing the Concentration of Substrate
At low values, the effect on enzyme activity:
Enzyme activity increases with additional
substrate molecules.
Beyond what temperature in humans do
increases have a different effect?
Beyond 40 degrees Celsius, enzyme activity
begins to decline.
When does increasing the enzyme
concentration have no effect?
When all substrate molecules are occupied
there is no further effect.
When does increasing the substrate
concentration have no effect?
When all enzyme active sites are occupied
there is no further effect.
2d.
What is the effect of high temperatures on enzyme molecules?
High temperatures cause enzyme molecules to change their shape, or denature, thus altering the
shape of the active site so that it no longer fits the substrate. A denatured enzyme cannot catalyze
reactions.
2e.
Increases in temperature and concentration have what underlying physical cause in common?
They act to increase the frequency of contact between enzyme molecules and substrate molecules
Scene 18
3.
pH Degrees: this diagram shows two
different enzyme molecules and where
they function best in the human digestive
tract.
3a.
What number represents neutral pH,
between acid and basic?
pH of 7
3b.
Where does pepsin work best and is that
environment acid or basic?
Pepsin works best in the acidic
environment of the stomach.
3c.
Where does trypsin work best and is that
environment acidic or basic?
Trypsin works best in the basic
environment of the small intestine.
Scene 19
4.
You’ve read and heard about bodies
preserved in peat bogs and glacial ice
for thousands of years. Considering what
you have learned so far about factors
affecting enzyme activity, what are some basic strategies for lowering enzyme activity during longterm food storage?
You can lower enzyme activity by 1) storing under low temperatures, 2) storing in
at a pH that does not favor enzyme activity, or 3) reducing the concentration of
enzymes in preparation for storage.
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
Complete Interactive Lessons # 3.
A review of enzyme structure and chemical interactions.
Interactive
Lesson
Enzyme Activity: Interactive Factors
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
View Scenes # 20 - 24 and complete the exercise below.
Learn about cofactors, coenzymes, inhibition and activation.
Multimedia
Presentation
Scene 20
1.
Enzyme Companions: the foods in this
picture (most of which are rather heavy
in cholesterol) supply materials needed
by the body to make cofactors. What are
cofactors and how are they derived?
A cofactor is a non-protein molecule required by some enzymes. Some cofactors
are derived from minerals such as calcium or iron. Other cofactors, derived from
organic molecules such as vitamins, are also called co-enzymes.
Scenes 21— 22
2.
Shutting the Door: this two-picture sequence portrays non-competitive inhibition.
Describe how step a leads to step b, using the correct terminology.
enzyme consequently
distorts the shape of its
active site, excluding the
substrate molecule.
Scene 23
3.
Blocking the Doorway: this
picture portrays
competitive inhibition.
Describe competitive inhibition and
give an example.
Competitive inhibitor molecules compete with substrate
molecules for the active sites of enzymes, thus blocking
enzyme activity. Penicillin is used as a broad-spectrum antibiotic against bacteria
because it acts as a competitive inhibitor, blocking the cell wall construction
enzyme common to many different kinds of bacteria.
(However, bacteria are evolving increased resistance to penicillin.)
Scene 24
4.
Opening the Door: this picture sequence portrays an enzyme activation process.
Using the correct terminology, describe the steps a, b and c.
In form an enzyme-substrate complex.
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
Complete Interactive Lessons # 4.
A review of the interactive factors of enzymes.
Interactive
Lesson
Complex Interactions
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
View Scenes # 25 - 32 and complete the exercise below.
Examine multi-subunit enzymes and metabolic pathways.
Multimedia
Presentation
Scenes 25 – 27
1.
Flip-Flop Switch: these two pictures show how potential substrate binding sites in
a multi-subunit enzyme can be turned on and off.
1a.
What is the molecule at label a and what is it doing?
Label a substrate molecule binding to an active site of the enzyme.
1b.
What is the molecule at label b, and what is its effect?
Label b points out an activator molecule bound of the enzyme. It stabilizes all
active sites in all protein subunits of the enzyme so that other substrate molecules
may bind to any available site.
1c.
What is the molecule at label c, and what is its effect?
Label c points out molecules can bind with the enzyme.
Scene 28
2.
Describe cooperativity. Scenes 29 – 31
3.
Stepping Along a Metabolic Pathway: this diagram shows a sequence of steps in
a hypothetical metabolic pathway.
3a.
What is a metabolic pathway?
A metabolic pathway is an enzyme-catalyzed series of reactions that builds-up or
breaks down a compound.
3b.
What is characteristic of the enzymes used in a metabolic pathway?
Each reaction in the sequence uses a different enzyme.
3c.
What is characteristic of the substrates in a metabolic pathway?
The product for one reaction becomes the substrate for the next reaction.
3d.
What is feedback inhibition and what does it accomplish?
Feedback inhibition occurs when the end product of a metabolic pathway serves
as an
, feedback inhibition prevents the cell from wasting chemical resources on
excessive production.
Scene 32
4.
(Hint: you can address the following question with what you have learned, but you
will need to puzzle about how it all fits together.)
Instructions for manufacturing enzymes are coded in DNA. As enzymes carry out
their jobs, even in complex metabolic pathways, they don’t need to ask the DNA
for further instructions. Where are the operating instructions stored?
Enzymes
Please load the CyberEd Biology Course Title: Enzymes
Complete Interactive Lessons # 5 and 6
A review of allosteric cooperation.
Interactive
Lesson
Somewhat like a jigsaw puzzle, the operating instructions for enzymes are stored
in
thei
Comprehensive Exam: Enzymes
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