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Chapter 8
An Introduction to Metabolism
Name ______________________
Date ______________________
Period _________
Matching: For each of the following definitions, choose the correct matching term from the list provided.
_____1.A quantitative measure of the amount of randomness or disorder of a
system.
_____2.An organic substance that is required for a particular enzymatic
reaction to occur.
_____3.Energy in motion.
_____4.A substance on which an enzyme acts.
_____5.An organic catalyst that greatly increases the rate of a chemical
reaction without being consumed by that reaction.
_____6.The total potential energy of a system.
_____7.A substance that increases the speed at which a chemical reaction
occurs without being used up during the reaction.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
Catalyst
Coenzyme
Energy
Enthalpy
Entropy
Enzyme
Free energy
Heat energy
Potential energy
Kinetic energy
Substrate
Thermodynamics
Multiple Choice: Read each question carefully. Choose the one best answer and write your selection in the
blank provided using CAPITAL letters.
_____8. Catabolic and anabolic pathways are often coupled in a cell because
a. both pathways use the same enzymes
b. the free energy released from one pathway is used to drive the other
c. the intermediates of a catabolic pathway are used in the anabolic pathway
d. their enzymes are controlled by the same activators and inhibitors
e. the activation energy of the catabolic pathway can be used in the anabolic pathway
_____9. A negative ∆G means that
a. the quantity G of energy is available to do work
b. the reactants have more free energy than the products
c. the reaction is exergonic
d. the reaction is spontaneous
e. all of the above are true
_____10. Which of the following metabolic processes can occur without a net influx of energy from some other
process?
a. ADP + Pi → ATP + H2O
b. 6 CO2 + 6 H2O → C6H12O6 + 6 O2
c. amino acids → protein
d. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
e. glucose + fructose → sucrose
_____11. According to the first law of thermodynamics,
a. all processes increase the order of the universe.
b. systems rich in energy are intrinsically stable.
c. energy is conserved in all processes.
d. matter can be neither created nor destroyed.
e. the universe constantly loses energy because of friction.
_____12. If an enzyme solution is saturated with substrate, the most effective way to obtain an even faster yield
of products is to
a. add more substrate.
d. add more of the enzyme.
b. heat the solution to 90°C.
e. add an allosteric inhibitor.
c. add a noncompetitive inhibitor.
_____13. Some bacteria are metabolically active in hot springs because
a. they use molecules other than proteins as their main catalysts.
b. their enzymes are completely insensitive to temperature.
c. their enzymes have high optimal temperatures.
d. high temperatures make catalysis unnecessary.
e. they are able to maintain a cooler internal temperature.
_____14. If an enzyme has been inhibited noncompetitively,
a. raising substrate concentration will increase inhibition.
b. the active site will be occupied by the inhibitor molecule.
c. more energy will be necessary to initiate the reaction.
d. the ∆G for the reaction it catalyzes will always be negative.
e. the inhibitor molecule may be chemically unrelated to the substrate.
_____15. Which of these is ATP?
a.
d.
b.
e.
c.
_____16. In the reaction to the right _____.
a. CD is a product
b. entropy has decreased
c. AC is a reactant
d. the products have less potential energy than
the reactants
e. the products have been rearranged to form
reactants
_____17. What is the correct label for "A" in the
diagram to the right?
a. ATP
b. energy of activation
c. substrate energy
d. enzyme energy
e. uphill
_____18. When substance A was added to an enzyme reaction, product formation decreased. The addition of
more substrate did not increase product formation. From this we conclude tat substance A could be
a. A cofactor
d. A competitive inhibitor
b. An allosteric enzyme
e. A noncompetitive inhibitor
c. Product molecules
_____19. In an experiment, changing the pH from 7 to 6 resulted in an increase in product formation. From this
we could conclude that
a. The enzyme became saturated at pH 6
b. The enzyme’s optimal pH is 6
c. This enzyme works best in a neutral pH
d. The temperature must have increased when the pH was changed to 6
e. The enzyme was in a more active conformation at pH 6
_____20. What is meant by induced fit?
a. Substrates are held in the active site by hydrogen and ionic bonds.
b. The binding of the substrate changes the shape of the active site, which can stress or bend
substrate bonds.
c. The active site creates a microenvironment ideal for the reaction.
d. A competitive inhibitor can out compete the substrate for the active site.
e. The binding of the substrate is an energy-requiring process.
Use the diagram below to answer the following questions.
N
L+M
_____21. Which of the following terms would best describe this reaction?
a. Nonspontaneous
d. coupled reaction
b. –∆G
e. anabolic
c. exergonic
_____22. Which of the following parameters does an enzyme raise?
a. ∆G
b. ∆H
c. Speed of a reaction
d. Free energy of activation
e. Equilibrium of a reaction
_____23. What is most directly responsible for the specificity of a protein enzyme?
d. Its cofactors
a. Its primary structure
e. The R groups of the amino acids in
b. Its secondary and tertiary structure
its active site
c. The conformation of its allosteric
site
_____24. When a cell breaks down glucose, only about 40% of the energy is captured in ATP molecules. The
remaining 60% of the energy is
a. Used to increase the order necessary for life to exist
b. Lost as heat because of the second law of thermodynamics
c. Used to increase the entropy of the system by converting kinetic energy into potential energy
d. Released when the ATP molecules are hydrolyzed
e. Stored in starch or glycogen for use later by the cell
_____25. Which of these statements about enzyme inhibitors is true?
a. A noncompetitive inhibitor does not change the shape of the active site.
b. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as
positive feedback.
c. Inhibition of enzyme function by compounds that are not substrates is something that only occurs
under controlled conditions in the laboratory.
d. The action of competitive inhibitors may be reversible or irreversible.
e. A competitive inhibitor binds to the enzyme at a place that is separate from the active site.
Short Answer: Read each question carefully and answer in essay format on a separate sheet of paper.
26. Amylase is a digestive enzyme that breaks down starch and is secreted in the mouth of humans. Amylase
functions well in the mouth but ceases to function once it hits the acidic stomach environment. Explain, in
detail, why amylase does not function in the stomach.
27. The ultimate goal of metabolism is to drive ATP synthesis. ATP is considered the energy currency of the
cell. Discuss how ATP couples endergonic and exergonic reactions and why it is so important in cellular
functions.
28. Explain how substrate concentration affects the rate of an enzyme-mediated reaction.
29. Enzymes are biological catalysts. Relate the chemical structure of an enzyme to its specificity and catalytic
activity.
30. Explain what is meant by "allosteric regulation" of an enzyme.
31. Design an experiment that could test the affect of either pH or temperature on the rate of an enzymatic
reaction. Be sure to include all of the key aspects of an experimental design and offer possible results.