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BioSc221/325
Exam 2
Name ______________________________
Multiple choice. (2 point each) Choose the one best answer to each of the following questions.
____ What is the fate of pyruvate in a microbe that uses respiration?
A.
B.
C.
D.
E.
It is reduced to lactic acid.
It is oxidized to lactic acid.
It is oxidized in the Krebs cycle.
It is reduced in the Krebs cycle.
It is catabolized in glycolysis.
____ What happens to ATP synthesis if the electron transport chain is stopped by
addition of an inhibitor?
A. ATP synthesis would stop due to a buildup of excess protons outside the
cell.
B. ATP synthesis will speed up due the excess buildup of protons outside
the cell.
C. ATP synthesis will stop due to the lack of protons outside the cell.
D. ATP synthesis will stop due to excess buildup of protons inside the cell.
E. None of the above
____ Which of the following is not an end product of fermentation?
A.
B.
C.
D.
E.
lactic acid
acetic acid
propionic acid
pyruvic acid
ethanol
____ The conversion of phosphoenolpyruvate (PEP) to pyruvic acid
A.
B.
C.
D.
releases CO2
involves the conversion of ADP to ATP
involves electron transport phosphorylation
none of the above
____ Which of the following is the best definition of fermentation?
A.
B.
C.
D.
The oxidation of a carbohydrate with organic molecules serving as final electron acceptors
The reduction of glucose to pyruvate
The complete catabolism of glucose to CO2 and H2O
The production of ATP from glucose
____ The primary purpose of catabolism is
A.
B.
C.
D.
E.
generation of ADP
biosynthesis
generation of ATP
degradation of organic molecules
oxidation of NADH to NAD+
____ What is the biological function of the reaction: pyruvic acid + NADH 2 -> lactic acid + NAD+.
A.
B.
C.
D.
E.
reduction of NAD+
oxidation of NADH2
oxidation of pyruvic acid
reduction of pyruvic acid
formation of lactic acid
____ Why do bacteria need to produce ribulose-5-phosphate via the hexose monophosphate shunt?
A.
B.
C.
D.
to replenish 6-phosphogluconate
to produce 2-keto-3-deoxy-6-phosphogluconate (KDPG )
to produce pentose sugars for nucleotide synthesis
to fix CO2
____ What can anoxygenic phototrophs use as an electron source?
A.
B.
C.
D.
E.
water
oxygen
sulfide
nitrate
CO2
____ The photosynthetic bacteria best suited for growth in the lower areas of a pond are the
A.
B.
C.
D.
E.
cyanobacteriu
heliobacteria
purple sulfur bacteria
green sulfur bacteria
purple nonsulfur bacteria
____ Which of the following major types of phototrophs carry out oxygenic photosynthesis?
A.
B.
C.
D.
E.
purple bacteria
green sulfur bacteria
green nonsulfur bacteria
Heliobacterium
cyanobacteria
____ Carotenoids function in which part of the photosynthetic apparatus?
A.
B.
C.
D.
Light harvesting center (antenna)
Reaction center
Electron transport chain
None of the above
____ How many molecules of ATP can potentially result from the reaction: pyruvic acid + NADH 2 -> lactic acid + NAD+?
A. 0
B. 1
C. 2
D. 3
E. 38
____ The cyanobacteria can fix gaseous nitrogen in structures termed
A.
B.
C.
D.
hormogonia
akinetes
cyanophycin
heterocysts
____ Some cyanobacteria, such as Synechococcus do not produce specialized structures to protect their nitrogenase so to avoid
harming nitrogenase they
A.
B.
C.
D.
fixi nitrogen at night
live in areas where there is low light intensity
consume the oxygen as soon as it is produced
form communities that keep out oxygen
____ In microorganisms that can synthesize all their cellular components, there is a central core of metabolic pathways
consisting of
A.
B.
C.
D.
E.
glycolysis
tricarboxylic acid cycle
hexose monophosphate shunt
all of the above
none of the above
____ The most metabolically versatile of the photosynthetic bacteria is
A.
B.
C.
D.
green sulfur
purple sulfur
purple nonsulfur
cyanobacteria
____ The major role of the tricarboxylic acid cycle in an autotroph or anaerobe is to provide
A.
B.
C.
D.
precursor metabolites
energy
energy and precursors
none of the above
____ An anapleurotic reaction is a reaction that
A.
B.
C.
D.
is used to ferment amino acids
produces multiple fermentation products
replenishes key intermediates of the TCA cycle
fixes carbon dioxide
____ In some cultures cyanobacteria are used as a high protein food source. These generally belong to the genus
A.
B.
C.
D.
Spirulina
Anabaena
Rhodococcus
Nobody would be foolish enough to eat cyanobacteria
____ A common compound in CO2 fixation and glucose catabolism that is a precursor metabolite (where the two pathways
meet) is
A.
B.
C.
D.
phosphoglyceric acid
glyceraldehyde-3-phosphate
pyruvic acid
phosphoenolpyruvate
____ An organism was isolated that could utilize gaseous nitrogen (N2) as sole source of nitrogen for growth. It would be safe
to assume that this isolate is a
A.
B.
C.
D.
E.
bacterium
fungus
plant
virus
any of the above
____ An enzyme complex found in both anoxygenic photophosphorylation and electron transport phosphorylation is
A.
B.
C.
D.
reaction center
bc1 complex
special pair
bacteriopheophytin
_____ Based on what you have learned about the elements that control synthesis of the enzymes for tryptophan synthesis, what
effect on enzyme activity would you expect under the following conditions: a mutation in the trpR gene, encoding TrpR the
tryptophan repressor, such that TrpR can bind DNA without the co-repressor
A.
B.
C.
D.
constitutive, high-level activity
no activity in the absence of tryptophan, high-level activity in the presence of tryptophan
high-level activity in the absence of tryptophan, no activity in the presence of tryptophan
no activity under any conditions
_____ Based on what you have learned about the elements that control synthesis of the enzymes for tryptophan synthesis, what
effect on enzyme activity would you expect under the following conditions: a mutation in the trpR gene coding for the
tryptophan repressor such that TrpR cannot bind tryptophan
A.
B.
C.
D.
constitutive, high-level activity
no activity in the absence of tryptophan, high-level activity in the presence of tryptophan
high-level activity in the absence of tryptophan, no activity in the presence of tryptophan
no activity under any conditions
_____ A repressible operon is important in regulating _____.
A.
B.
C.
D.
Amino acid synthesis
DNA replication
Sugar metabolism
ATP synthesis
_____ Catabolite repressor protein (CRP) binds to DNA when bound to ____ and ____ expression of catabolic operons such as
the lac operon.
A.
B.
C.
D.
E.
Glucose, represses
Glucose, activates
cAMP, represses
cAMP, activates
Lactose, represses
_____ The site of interaction between RNA polymerase and DNA that initiates transcription is called the ___.
A.
B.
C.
D.
Pribnow box
Shine-Dalgarno sequence
Promoter
Operator
___ Quorum sensing systems use ___ to determine cell density.
A.
B.
C.
D.
cell-cell contact
autoinducer
luminescence
phosphotransferase
____ Promoter strength is determined by
A.
B.
C.
D.
the DNA sequence of the promoter region
the number of operators
how close the promoter is to the start of transcription
the DNA sequence of the ribosome binding site
____ Protein involved in transcriptional termination.
A.
B.
C.
D.
core enzyme
stem loop
rho
sigma
____ Genes encoding the enzymes required for utilization of maltose as a growth substrate are likely to be controlled by what
type of repressor?
A. inducible
B. repressible
C. constitutive
____ In two-component regulatory systems a signal is relayed to the regulator protein by
A.
B.
C.
D.
phosphorylation
adenylation
autoinducer
a peptide
____ Genes encoding the enzymes required for synthesis of the amino acid tyrosine are likely to be controlled by what type of
repressor?
A. inducible
B. repressible
C. constitutive
____ Several genes that are transcribed in the same direction and share the same promoter are called a(n)
A.
B.
C.
D.
operator
operon
polylinker
polypromoter
____ Small protein that associates with bacterial RNA polymerase to facilitate promoter recognition and is released during
transcription.
A.
B.
C.
D.
alpha
beta
gamma
sigma
____ Genes that are expressed at the same level at all times are said to be
A.
B.
C.
D.
constitutive
inducible
repressible
activated
____ Most prokaryotic promoters have a two-part consensus sequence that consists of a
A.
B.
C.
D.
promoter and terminator
promoter and operator
activator and operator
–10 and –35 region
Short answer. (variable points)
(2) The Fnr protein of E. coli can function as both a repressor and an activator. Describe the likely location of the DNA
binding site for Fnr relative to the promoter when it is functioning as an:
Activator
Repressor
(4) In the lac operon expression of the enzyme -galactosidase is under the control of the lac repressor (LacI) which binds at
the lac operator (lacO). Complete the table with High if -galactosidase is expressed at high levels under the conditions
described or Low if -galactosidase is expressed at low levels under the conditions described. Assume glucose is not present.
Mutation
lacI- - doesn’t make LacI
Lactose present
Lactose absent
lacIs - LacI can’t bind lactose
(1) Bacteriochlorophylls can be found with very diverse absorbance spectra. What advantage does this provide for the
phototroph?
(1) Anoxygenic photophosphorylation is also called cyclic photophosphorylation. Since the electrons can be recycled, why do
these organisms need an electron donor?
(4) The cartoon below depicts a standard electron transport chain from NADH/H + to O2. How many coupling sites (locations
where protons are translocated) are present in this electron transport chain? Indicate the location of each coupling site with an
arrow and an H+
(2) In the TCA cycle, one other hydrogen carrier is used in addition to NADH. Electrons from this molecule (FADH) follow
nearly the same pathway to oxygen but only yield 2 ATP. Now that you know how electron transport is coupled to ATP
synthesis, predict the reason why only 2 ATP may arise from FADH oxidation.
(1) Give one reason why an organism would want to hydrolyze a molecule of ATP to make the ATP synthase enzyme to run
“backwards”.
(4) Here are several electron carriers found in an electron transport chain and their respective redox potentials. Draw an
electron transport chain with the electron carriers in the correct order.
Cytochrome c (+300mV), Quinone (+60mV), Ferrodoxin (-200mV), Iron-Sulfur center (-100 mV), Cytochrome b (+100 mV)
Electron
donor →
Electron
→
acceptor
Short Essay Questions. Please answer 3 of the following 4 short essay questions (6 points each - 6 bonus points possible for
answering all 4 questions)
What are some basic differences and similarities between fermentation and respiration using glucose as the carbon and energy
source?
In the first section of this class we discussed stromatolites which are fossilized microbial mat communities. The microbial
mats consisted of layers of different prokaryotic phototrophs. Based on what you have learned about the properties of the
different kinds of phototrophs in this section of the course, explain the basis for this layering phenomenon and the types of
organisms you would expect to find in the different layers.
It has been assumed for many years that plants account for most of the “fixed” carbon on earth. However, microbes are being
discovered in significant quantities in environments such as the open ocean and in subsurface areas and it is now becoming
clear that microbes account for most of the “fixed” carbon on earth. Consequently, we have also discovered that microbes have
evolved several mechanisms for “fixing” carbon dioxide. Briefly discuss three mechanisms of carbon dioxide fixation found in
microbes.
Draw a growth curve of E. coli transferred from a stationary phase culture growing in minimal glucose medium to a minimal
medium containing a small amount of glucose and lactose. Show optical density vs. time. Describe what is happening at
various key points and why?