Cell Biology Exam #2-Spring 2013
Name___________________
Lab section____________________
Multiple choice. Choose the best answer (2 points each)
1._____ Which of the following statements is TRUE concerning catabolic pathways?
A) They build up complex molecules such as protein from simpler compounds.
B) They combine molecules into more complex and energy-rich molecules.
C) They involve endergonic reactions that break complex molecules into simpler ones.
D) They are usually coupled with anabolic pathways to which they supply energy in the
form of ATP.
E) They are spontaneous and do not need enzyme catalysis.
2._____An endergonic reaction is characterized by: A) its tendency to occur
spontaneously. B) the net release of free energy. C) a value for delta G which is positive.
D) reactants that have a higher free energy than products. E) all of the above
3._____ Why is ATP an important molecule in metabolism?
A) Its synthesis is exergonic
B) It is extremely stable.
C) Its hydrolysis is endergonic.
D) It is readily obtained from an organism's environment.
E) Its phosphate bonds are easily formed and broken.
4._____ Which of the following does not have to be true if the reaction
AB + CD AC + BD occurs spontaneously?
A) The delta G of the reaction must be negative. B) the reaction must be endergonic.
C) the environment has adequate thermal energy to meet the energy of activation
requirement. D) The bonds must have absorbed enough energy to become unstable.
E) all of the above must be true
5._____ Which of the following reactions could be coupled to the reaction ATP + H2O
ADP + Pi (-7.3 kcal)? Numbers in () indicate the delta G of each reaction)
A)
B)
C)
D)
E)
CP C + Pi (-4 kcal)
A + Pi AP (+9 kcal)
E + Pi EP (+5 kcal)
B + Pi BP (+8 kcal)
DP D + Pi (-10 kcal)
6._____What best characterizes the role of ATP in cellular metabolism?
A) The release of free energy during the hydrolysis of ATP heats the surrounding
environment. B) Its exergonic hydrolysis is coupled to an endergonic process via the
formation of a phosphorylated intermediate. C) It is catabolized to carbon dioxide and
water. D) The delta G associated with its hydrolysis is positive. E) The polar phosphate
groups assist in the alignment of polar substrates as they enter an enzyme's active site.
7._____Succinylcholine is structurally almost identical to acetylcholine, but if
combined with the enzyme that normally hydrolyses acetylcholine, the enzyme is
no longer able to hydrolyze acetylcholine. This suggests that
A) succinylcholine must be a competitive inhibitor with acetylcholine.
B) the active site must have the wrong configuration to permit succinylcholine binding.
C) succinylcholine must be a noncompetitive inhibitor.
D) the energy of activation barrier for succinylcholine hydrolysis is higher than for
acetylcholine.
8. _____Researchers measured the reaction rate of an enzyme in a series of
experiments where substrate concentration was sequentially increased by 10
percent. Initially they observed a linear increase in rate, but eventually the rate
leveled; after which time additional substrate had no effect on reaction rate. How can
this be explained?
A) The enzyme was saturated.
B) A high concentrations the substrate becomes an allosteric inhibitor.
C) A high concentrations the substrate becomes a competitive inhibitor.
D) A high concentrations the substrate becomes a noncompetitive inhibitor.
E) A high concentrations the substrate feedback inhibition begins.
9._____ During a laboratory experiment, you discover that an enzyme-catalyzed
reaction has a Delta G = -20 kcal/mole. You double the amount of enzyme in the
reaction and the Delta G now equals:
A) -10 kcal/mole; B) -20 kcal/mole; C) +40 kcal/mole; D) -40 kcal/mole; E) It is not
possible to calculate the answer with the data given.
10._____ The word 'protease' refers to enzymes that . . . A) are constructed of protein.
B) are constructed of RNA. C) hydrolyze proteins. D) contain an allosteric site.
Question # 11 is based on the following information. A series of enzymes catalyze the
reaction X--Y--Z--A. Product "A" binds to the enzyme that converts X to Y at a
position remote from its active site. This binding decreases the activity of the enzyme.
11._____ In this example, substance X is:
A) the product. B) an allosteric inhibitor. C) a substrate. D) a coenzyme. E) an
intermediate.
12._____ Fermentation is essentially glycolysis plus an extra step in which pyruvic acid is
reduced to form lactic acid or alcohol and carbon dioxide. This last step: A) removes
poisonous oxygen from the environment. B) extracts a bit more energy from glucose.
C) enables the cell to recycle NADH into NAD+. D) inactivates toxic pyruvic acid.
E) enables the cell to make pyruvic acid into substances it can use.
13._____ For the following question; 1=glycolysis, 2=citric acid cycle; 3=ETS. In which of
these is ATP produced by oxidative phosphorylation?
A)1; B)2; C)3; D)1&2; E) 1&3
14._____ For the following question; 1=glycolysis, 2=citric acid cycle; 3=ETS. In which of
these is NADH oxidized?
A)1; B)2; C)3; D)1&2; E) 1&3
15._____ Which of the following statements is false? A) oxidative phosphorylation
produces 32 of the 38 ATP produced from every glucose molecule; B)every NADH2
produced by the Citric acid cycle adds 6 H+ to the hydrogen pool in the intermembrane
space; C) glycolysis produces less net molecules of ATP than fermentation; D) for every 2
H+ ions that go through the ATPase channel, 1 ATP can be made.
16._____ Which metabolic pathway is common to both fermentation and aerobic
cellular respiration? A) Citric acid cycle B) electron transport chain C) glycolysis
D) synthesis of acetyl-COA from pyruvate E) reduction of pyruvate to lactate
17.____ Glycolysis starts with __________ and ends with __________:
a) glucose ... glyceraldehyde-3-phosphate. B) glucose ... diphosphoglycerate.
C) glucose ... pyruvate. D) pyruvate ... acetyl CoA. E) glucose ... acetyl CoA.
18._____ During respiration in a eukaryotic cell, the electron transport chain is located
in or on: A) the cytoplasm B) the matrix of the mitochondrion C) the inner membrane
of the mitochondrion D) the intermembrane space of the mitochondrion E) None of
the above
19._____ Suppose a molecule of glucose is fermented by a cell. One of the end products
is CH3CH2OH. Without even knowing the name of this product, how do you know that
energy could still be extracted from it?
A) The OH is an energy-rich molecule. B) The product contains C-H bonds from which
energy can be harvested (the hydrogens are potential energy). C) The product can be
converted back to glucose through the Citric acid cycle and then sent through aerobic
respiration. D) It is phosphorylated and thus energy rich.
20._____In addition to ATP, what are the end products of glycolysis? A) CO2 and H2O
B) CO2 and ethyl alcohol C) NADH and pyruvate D) CO2 and NADH E) H2O and ethyl
alcohol
21._____ All of the following reactions occur in the mitochondria except:
A) conversion of pyruvate to ethanol; B) conversion of pyruvate to acetyl Co-A;
C) CITRIC ACID cycle; D) the electron transport system; E) oxidative phosphorylation.
22._____ For the following question; 1=glycolysis, 2=citric acid cycle; 3=ETS. In which of
these is ATP used ?
A)1; B)2; C)3; D)1&2; E) 1&3
23.______ The most CO2 released during cell respiration is from:
A) glycolysis. B) the citric acid cycle. C) lactate fermentation. D) electron transport.
E) oxidative phosphorylation.
24._____ During photosynthesis in a eukaryotic cell, the Calvin cycle reactions occur in:
A) the thylakoid membrane; B) the (inner) thylakoid space (lumen);
C) the stroma; D) the matrix; E the cytosol
25.______ In the light dependent reactions of photosynthesis, light energy is used to
remove electrons and protons from water and ultimately transfer them to : A) RUBP;
B) NADP; C) oxygen; D ATP;
26._____ This event does not directly contribute to the formation of the H+ gradient
during the light dependent reactions of photosynthesis: A) the reduction of CO2 by
NADPH; B) the light dependent splitting of water in the thylakoid space; C) the electron
transport system in the thylakoid membrane; D) the reduction of NADP in the chloroplast
stroma.
27._____ While on a field trip to the tropical rain forest, you discover a plant with
orange leaves. It contains a photosynthetic pigment called orangophyll. Tests show
that orangophyll absorbs purple, blue, and green light most strongly, and it reflects
orange, red, and yellow light. You plan to grow these plants and sell them. What
wavelengths of light should your grow-tubes supply for best growth? A) Orange, red,
and yellow light because the color of the leaves indicates the best wavelengths;
B) Purple, blue, and green light because orangophyll absorbs those wavelengths;
C) Red and blue light because those are the best wavelengths for photosynthesis;
D) Orange, red, and yellow light because orangophyll reflects those wavelengths;
E) Purple, blue, and green light because orangophyll reflects those wavelengths.
28._____ A porphyrin ring containing an atom of magnesium and a long hydrocarbon
“tail” are important functional parts of this molecule? A) chlorophyll; B) ATP;
C) NADP; D) photosystem I; E) photosystem II.
29._____ Which of the following statements best represents the relationship between
the light reactions and the Calvin cycle? a) the light reactions provide ATP and NADPH
to the Calvin cycle, and the cycle returns ADP, Pi, and NADP+ to the light reactions
b) the light reactions provide ATP and NADPH to the carbon fixation step of the Calvin
cycle, and the cycle provides water and electrons to the light reactions c) the light
reactions supply the Calvin cycle with CO2 to produce sugars, and the Calvin cycle
supplies the light reactions with sugars to produce ATP d) the light reactions provide
the Calvin cycle with oxygen for electron flow and the Calvin cycle provides the light
reactions with water to split e) there is no relationship between the light reactions and
the Calvin cycle
30._____ This leaf structure can open and close depending on environmental conditions
and allow gas exchanges (CO2 andO2) to occur between the leaf and the atmosphere:
A) cuticle; B) stomate; C) vascular bundle; D) mesophyll
31._____ Which of the following sequences correctly represents the flow of electrons
during photosynthesis? A) NADPH —› O2 —› CO2; B) H2O —› NADPH —› Calvin cycle;
C) NADPH —› chlorophyll —› Calvin cycle; D) H2O —› photosystem I —› photosystem II;
E) NADPH —› electron transport chain —› O2.
32._____ Which of the following statements is a correct distinction between autotrophs
and heterotrophs? A) Only heterotrophs require chemical compounds from the
environment; B) Cellular respiration is unique to heterotrophs; C) Only heterotrophs
have mitochondria; D) Autotrophs, but not heterotrophs, can nourish themselves
beginning with CO2 and other nutrients that are entirely inorganic; E) Only
heterotrophs require oxygen.
33._____ This is an adaptation of some plants living in hot dry environments to
counteract the harmful effects of photorespiration: A) bundle sheath cells. B) CO2
fixation using the enzyme PEP carboxylase. C) Fixing Co2 into organic acids at night.
D) C-4 photosynthesis. E) all of the above
34._____ How is photosynthesis similar in C4 and CAM plants?
A) In both cases, only photosystem I is used.
B) Both types of plants make sugar without the Calvin cycle.
C) In both cases, rubisco is not used to fix carbon initially.
D) Both types of plants make most of their sugar in the dark.
E) In both cases, thylakoids are not involved in photosynthesis.
5. (4 points each). Agree or disagree with the following statements. In either case, fully
defend your answer.
A. Because cells are open systems, they can exist and appear to violate the Second Law of
Thermodynamics.
B. The process of cellular respiration has another important function in metabolism in
addition to its role of breaking down food molecules to produce energy.
C. Photosystem I could not carry out the reduction of NADP into NADPH for a sustained
period of time without Photosystem II operating as well.
35. (20 points).
Answer any 2 of the following 3 essays (10
points each):
A. Draw an energy profile (free energy on the Y axis and progress of reaction on the X axis)
of an exergonic enzyme catalyzed and an uncatalyzed chemical reaction (two plots on
the same graph). Label the following for both reactions on your energy profile: a) delta
G, b) energy of activation, and 3) transition state. Propose one mechanism (involving
the formation of an enzyme substrate complex and induced fit) that explains the
different energy profile of the catalyzed and uncatalyzed reaction.
B. Based upon your knowledge of the basic differences between fermentation and aerobic
respiration, explain why aerobic respiration of glucose is so much more efficient (almost
19 X more efficient) at producing ATP than fermentation. You don't have to describe
both processes in complete detail to answer this question, concentrate on how the
basic differences in the two processes account for the large difference in efficiency of
ATP production/glucose.
C. For both the light reactions and the Calvin cycle (light independent reactions)
describe the a) location, b) raw materials used, and c) products formed for each process.
Describe the role that Photosystems I and II play in the light dependent reactions and how
the two photosystems interact with one another.
1._____ According to the hypothesis described in the passage, the bacteria that entered primitive
eukaryotic cells were able to carry out which of the following functions that the primitive
eukaryotic cells could NOT?
A. Glycolysis
B. Krebs cycle and electron transport
C. Cell division
D. Transcription and translation
2._____ The chemical gramicidin inserts into membranes and creates an artificial pathway for
proton movement. Based on Figure 1, if mitochondria are treated with gramicidin, the rate of
ATP synthesis will most likely:
A.
B.
C.
D.
increase, because of increased proton movement back into the mitochondria.
decrease, because of a decreased rate of hydrogen-atom donation by NADH.
decrease, because the proton gradient will rapidly reach equilibrium.
not be altered, because sufficient protons will remain between the membranes to generate
ATP.
3._____ Which of the following pieces of evidence most strongly supports the hypothesis of
mitochondrial origin described in the passage?
A.
B.
C.
D.
Mitochondria have fewer genes than typical bacterial cells have.
Mitochondria contain hundreds of different enzymes.
The diameters of mitochondria and typical present-day bacteria are approximately equal.
Nitrogen-fixing bacteria live symbiotically inside the cells of present-day plants.
4_____. To support the symbiotic hypothesis presented in the passage, mitochondria should be
similar to bacteria in which of the following ways?
A.
B.
C.
D.
They should use 80S ribosomes.
They should be incapable of binary fission.
They should have circular DNA.
They should be capable of anaerobic respiration.
5. _____ The chemical valinomycin inserts into membranes and causes the movement of K+ into
the mitochondria. Based on Figure 1, if mitochondria are treated with valinomycin, the rate of
ATP synthesis in the mitochondria will most likely:
A. decrease, because the K+ will compete with protons at the active site on ATP synthetase.
B. decrease, because movement of K+ into the mitochondrial compartments will disrupt proton
movement into the intermembrane space.
C. increase, because the net positive charge in the mitochondria will cause increased
movement of protons into the intermembrane space.
D. increase, because the additional positive charge will further activate ATP synthetase.