Download BioSc221/325 Exam 2 Name

BioSc221/325
Exam 2
Name ______________________________
Multiple choice. (1 point each) Choose the one best answer to each of the following questions.
1. __B__ Biochemical synthesis of new cell material is called
A. Metabolism
B. Anabolism
C. Catabolism
D. Synthatabolism
2. __A__ The suffix -troph is derived from a Greek work meaning
A. to feed
B. to assimilate
C. to energize
D. to break down
3. __A__ Chemoorganotrophs use which of the following as an energy source?
A. Organic compounds
B. Inorganic compounds
C. Both organic and inorganic compounds
D. Light
4. __C__ A fastidious organism is
A. oxygen sensitive
B. temperature sensitive
C. nutritionally demanding
D. atmospheric pressure sensitive
5. __B__ If ∆G0 is positive
A. the reaction is exergonic and requires the input of energy.
B. the reaction in endergonic and requires the input of energy.
C. the reaction is exergonic and energy will be released.
D. the reaction is endergonic and energy will be released.
6. __B__ Which statement is true?
A. Coenzymes are generally bound tightly to their respective enzymes.
B. Prosthetic groups are generally bound tightly to their respective enzymes.
C. Coenzymes and prosthetic groups are both bound tightly to their respective enzymes.
D. Coenzymes and prosthetic groups are technically not bound to any enzymes.
7. _ D_ In an electron carrier system, the net energy change is determined by the difference in reduction potentials between the
A. primary electron donor and the terminal electron donor.
B. primary electron acceptor and the terminal electron acceptor.
C. primary electron acceptor and the terminal electron donor.
D. primary electron donor and the terminal electron acceptor.
8. __B__ The Embden-Meyerhof Pathway is another name for
A. the citric acid cycle
B. glycolysis
C. electron transport
D. NADH production
9. __A__ In glycolysis
A. the crucial product is ATP; the fermentation products are waste products.
B. the crucial product is ethanol or lactate; ATP is a waste product.
C. the crucial product is CO2 ; ATP is a waste product.
D. the crucial product is not relevant because glycolysis is not a major pathway.
10. __B__ In chemiosmosis
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A. OH accumulates on the outside of the membrane while H accumulates on the inside.
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B. OH accumulates on the inside of the membrane while H accumulates on the outside.
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C. both OH and H accumulate on the inside of the membrane.
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D. both OH and H accumulate on the outside of the membrane.
11. __A__Which statement is not true? Uncouplers prevent ATP synthesis
A. by interfering with electron flow.
B. by creating leaky membranes.
C. without affecting electron transport.
D. by destroying the proton motive force.
12. __B__ The chemical substance that enters the citric acid cycle for further metabolism is __
A. ethyl alcohol
B. acetyl-CoA
C. adenosine triphosphate
D. pyruvic acid
13. __D__ Which of the following occurs in the absence of oxygen?
A. Fermentation
B. Anaerobic respiration
C. Anoxygenic photosynthesis
D. All of the above.
14. __B__ Most chemolithotrophs are
A. phototrophs
B. autotrophs
C. heterotrophs
D. organotrophs
15. __A__For a carbon source, chemoorganotrophs generally use such compounds as
A. glucose
B. carbon dioxide
C. triglycerides
D. sunlight
16. __C__ For each molecule of pyruvate that enters the citric acid cycle, how many molecules of CO2 are generated?
A. 1
B. 2
C. 3
D. 6
17. __B__ Whether an organism is classified as a photoheterotroph or a photoautoroph depends on its
A. energy source.
B. carbon source.
C. oxygen requirements.
D. All of the above.
18. __C__ How many ATP result from the transfer of electrons from NADH to O2 through the electron transport chain?
A. 1
B. 2
C. 3
D. 6
19. __A__To describe a type of photosynthesis as "oxygenic" implies that
A. oxygen is produced
B. oxygen is consumed
C. oxygen functions as a catalyst
20. __A__ Which statement is true?
A. The cytochromes contain iron; chlorophyll contains magnesium.
B. The cytochromes contain magnesium; chlorophyll contains iron.
C. Both the cytochromes and chlorophyl contain iron but not magnesium.
D. Both the cytochromes and chlorophyl contain magnesium but not iron.
21. __C__ Chlorophyl a is green because it
A. absorbs green light and reflects red and blue light..
B. absorbs red and green light and reflects blue light.
C. absorbs red and blue light and reflects green light.
D. absorbs green light and what it reflects is irrelevant.
22. __D__ The carotenoids and the phycobilins
A. are involved in the capture of light energy.
B. function as accessory pigments.
C. are photoprotective.
D. All of the above.
23. __B__ Non-unit membrane structures known as chlorosomes and functioning in photosynthesis are characteristic of
A. heliobacteria
B. green sulfur bacteria
C. purple phototrophic bacteria
D. myxotrophic bacteria
24. __C__ When electrons are forced backwards, against the thermodynamic gradient, to reduce NAD+ to NADH, the process
is called
A. reverse proton motive force.
B. reverse reduction
C. reverse electron flow
D. reverse energy flow
25. __D__ Photosystem II in oxygenic phototrophs is able to accept electrons from water because
A. excitation of P680 by light results in a redox potential of -0.75V.
B. pheophytin, the next electron carrier has a redox potential of -0.5V.
C. noncyclic electron flow doesn't require electrons to come from cytochrome c.
D. P680 has an initial redox potential of +1.0V.
26. __C__ Plastocyanin is
A. a membrane bound sac found in certain bacteria.
B. a photosynthetic pigment found in all phototrophic bacteria.
C. a copper-containing protein that donates electrons in photosystem II
D. a blue-green bacterium known for its unusual photoreactive complex.
27. __A__ The Calvin cycle
A. is responsible for the fixation of CO2 .
B. utilizes only ATP.
C. requires phosphofructokinase and pyruvate decarboxylase
D. all of the above
28. __A__ Which of the following phototrophs are most sensitive to sulfur and are also often capable of respiration or
fermentation?
A. purple non-sulfur
B. purple sulfur
C. green sulfur
D. heliobacteria
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29. __D__ The electron carrier used by the green anoxygenic phototrophs to directly reduce NAD is called
A. iron sulfur protein
B. bacteriochlorophyll
C. plastocyanin
D. ferrodoxin
30. __D__ Phototrophic bacteria responsible for up to 50% of CO2 fixation in aquatic environments belong to the
A. purple bacteria
B. green bacteria
C. heliobacteria
D. cyanobacteria
31. __C__ Compounds produced by cyanobacteria that are responsible for the earthy odors in water supplies contaminated by
these organisms are called
A. geobacteria
B. gleothece
C. geosmins
D. geodecans
32. __A__ A specialized pigment that protects cyanobacteria from UV damage is called
A. scytonemin
B. cyanophycin
C. phytoerythrin
D. akinete
33. __B__ The bc1 complex serves as a coupling site in both photophosphorylation and electron transport phosphorylation.
Protons are released to the exterior of the cell due to the action of a
A. proton pump.
B. Q-cycle.
C. terminal electron acceptor.
D. primary electron donor.
Matching. (1 pt. each) Match the phototrophic genera in the left column with the appropriate description in the right column.
__A__ Synecococcus, Gleothece
A. Unicellular, used to study circadian rhythms.
__D__ Rhodospirillum, Chromatium
B. Filamentous, some used as a popular food source
__G__ Fischerella, Stigonema
C. Anoxygenic green bacteria
__F__ Pleurocapsa, Dermocarpa
D. Anoxygenic purple bacteria
__E__ Anaebaena, Nostoc
E. Filamentous, produce specialized nitrogen fixing cells called heterocysts.
__B__ Oscillatoria,Spirulina
F. Produce offspring called baeocytes by internal division
__C__ Chlorobium
G. Branching filaments.
Short answer. (1-2 pts each)
Phycobiliproteins occur as high-molecular-weight aggregates known as ____Phycobilisomes____. Cells with an
increased number of these structures are grown at __________Lower________________ (higher/lower) light intensities.
In synthesizing one molecule of glucose from carbon dioxide, the Calvin cycle must be run ___Six (6)_____ times.
When external electron acceptors are not available in anoxic environments, carbon is catabolized by ____Fermentation____.
Explain the difference between a chemically defined (minimal) medium and an undefined (complex) medium.
A chemically defined medium is one in which all the chemical constituents are precisely known whereas as a complex
medium contains components for which the exact chemical composition is not known such as yeast extract or beef
extract.
Rhospirillum rubrum is capable of growing either photoheterotrophically or chemoorganotrophically. What do these terms
mean?
Photoheterotroph means that the organism uses light as an energy source and organic compounds as carbon sources.
Chemoorganotroph means that the organism uses organic compounds as an energy source. It does not necessary mean
that the organism uses organic compounds as carbon source.
You are an anoxygenic green bacterium that contains chlorophyll a. What are your two favorite colors and why?
Your favorite colors are red and blue because those are the colors that excite the chlorophyll a pigment for
photophosphorylation.
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Some bacteria are capable of fermenting glucose to 2 molecules of lactate and 2 protons (H+). What is the free energy yield?
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∆G0 f values - glucose (-917kJ), lactate (-517kJ), H (-39kJ @ pH7). Theoretically, how many ATP would this produce?
The theoretical free energy yield would be -195 kJ. This would be enough energy to produce 6 ATP at a cost of -32
kJ/ATP
Complete the following diagrams. (0.5 points each item)
Identify the steps at which NAD(P)H is generated by circling the appropriate reaction on the following diagram of the citric
acid cycle
Using the bar on the left side of the page, draw an electron tower indicating the relative positions of the following redox
couples. Circle those compounds that would act as electron donors to the fumarate/succinate couple (+0.03). Be sure to label
the bar appropriately.
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2H+/H2 (-.42)
NAD+/NADH (-.32)
Ubiquinoneox/ Ubiquinonered (+0.11)
NO 3-/NO 2- (+0.42)
1/2O 2 /H2O (+0.82)
2H / H2 (-.42)
NAD /NADH (-.32)
Ubiquinoneox/ Ubiquinonered (+0.11)
NO3 /NO2 (+0.42)
1/2O2 /H2 O (+0.82)
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Short Essay Questions. Please answer 3 of the following 4 short essay questions (5 points each - 5 bonus points possible for
answering all 4 questions)
Describe the process of aerobic electron transport phosphorylation beginning with NADH as the primary electron donor.
Include all electron carriers and all coupling sites. Include a description of the relative redox potentials of the various electron
carriers.
NADH dehydrogenase removes hydrogen atoms from NADH with hydrogen atoms donated to Flavoprotein
Flavoprotein donates electrons to iron sulfur protein - Protons are released outside the cell (coupling iste 1)
Iron sulfur protein donates electrons to quinone
Quinone accepts hydrogen atoms so must acquire protons from cytoplasm to go along with the electrons
Quinone donates only electrons to cytochrome bc1 - Q cycle results in protons outside of cell (coupling site 2)
Cytochrome bc1 donates electron to cytochrome c
Cytochrome c transfers electron to cytochrome a (terminal oxidase) - protons are "pumped" out of cell (coupling site 3)
Cytochrome aa 3 reduces O2 to H2 O.
Phosphorylation takes place as protons return to the inside of the cell by passing through ATP synthase which uses 4
protons to synthesize one ATP from ADP + Pi
Describe either oxygenic or anoxygenic photophosphorylation from the primary electron donor to the terminal electron
acceptor. Include a description of the relative redox potentials of the various electron carriers.
Anoxygenic (cyclic photophosphorylation)
P870 (E0 ' = +0.5 ) accepts electrons from H2S, organic compounds etc.
Absorption of light energy excites the special pair and E0 ' goes to -1.0
Electrons donated to bacteriopheophytin (Bph)
Bph donates electrons to intermediate quinone
Quinone exchanges with quinone "pool"
Quinone pool reduces bc1 complex where the Q cycle generates PMF
bc1 complex reduces cytochrome c2
cytochrome c2 reduces special pair to start cycle again
no net input or consumption of electrons
Oxygenic photosynthesis (Z scheme)
Starts at Photosystem II
P680 - E0 ' = +1.0 - can actually accept electrons from H2 0 releasing H+ and O2 (hence oxygenic photosynthsis)
Excited P680 - E0 ' = -0.5 - donates e- to pheophytin
Electron flow similar to anoxygenic electron flow but bf instead of bc1 then on to plastocyanin
Plastocyanin transfers electrons to Photosystem I (P700) (note - non-cyclic electron flow)
Excited P700 transfers electrons to a carrier at E0 ' = -1.1
Electron carrier reduces ferrodoxin (E0 ' = -0.39)
Ferrodoxin is electronegative enough to reduce NAD(P)+
Compare and contrast fermentation and respiration. Describe how proton motive force is generated in each type of
metabolism.
Respiration is defined as the oxidation of a compound coupled to reduction of an external terminal electron acceptor.
Fermentation is defined as a series of internally balanced redox reactions that release energy.
Respiration has several advantages over fermentation.
Complete oxidation of carbon compounds to CO2
Greater difference in reduction potential
Respiration produces ATP via electron transport phosphorylation which has a high net yield of ATP per glucose
oxidized.
Fermentation produces ATP via substrate-level phosphorylation which has a low net yield of ATP per glucose oxidized.
PMF is generated during respiration via the reactions associated with the electron transport chain.
PMF is not generated in fermentation therefore ATP must be hydrolyzed via the ATP synthase to produce PMF for
motility and transport.
What is chemiosmosis? How were uncouplers and inhibitors used to support the chemiosmotic theory?
Chemiosmosis is the establishment of a proton motive force by the separation of protons from electrons at the
membrane. As protons are released outside the cytoplasmic membrane an electrical potential is generated across the
cytoplasmic membrane that can be use for ATP synthesis.
Inhibitors block ATP synthesis either by stopping electron transfer or stopping ATP synthase.
Stopping electron transfer stops ATP synthesis because the H+ gradient is not formed.
Stopping ATP synthase stops ATP synthesis but also slows down electron transfer - no dissipation of H+ gradient
Uncouplers create proton permeable holes in the membrane which stops ATP synthesis because the uncoupler creates a
site of less resistance than ATP synthase for protons to enter the cytoplasm.