Patho 1

1.

1 point

Industrial nitrogen fixation is achieved through the Haber process in which:

N2 is reduced catalytically by H2 at ambient temperature

N2 is hydrogenated by CH4 at extreme temperature and pressure

nitrate and nitrite are chemically converted to NH at ambient temperature

all of the above

2.

1 point

Gene expression of nitrogenase through NtrC is down-regulated in high concentrations of:

ammonium

nitrate

nitrogen

carbon dioxide

3.

1 point

How does bacteriorhodopsin couple photoexcitation with proton pumping?

Bacteriorhodopsin has a proton channel domain.

Bacteriorhodopsin makes the membrane porous to protons.

Light-induced conformational changes of retinal cause the protein to extrude one proton.

all of the above

4.

1 point

How many turns of the Calvin cycle does it take to provide one molecule of glyceraldehyde-3-phosphate into the biosynthesis of glucose?

1

3

6

2

5.

1 point

Based on the number of enzymes involved in its biosynthesis, which of the following is the most complex amino acid specified by the genetic code?

tryptophan

phenylalanine

tyrosine

leucine

6.

1 point

The incorporation of NH4+ into 2-oxoglutarate is the first step in nitrogen assimilation in bacterial cells. This reaction is catalyzed by the enzyme ________ and produces __________.

glutamate dehydrogenase (GDH); glutamate

glutamine synthase (GS); glutamine

glutamate synthase (GOGAT); glutamate

none of the above

7.

1 point

What is denitrification?

conversion of nitrate or nitrite to N2 by anaerobic respirers

oxidation of NH4+ to nitrate or nitrite by lithotrophs

conversion of N2 to NH4+

all of the above

8.

1 point

he most ancient CO2 fixation pathway in anaerobic phototrophic bacteria and archaea is:

the reverse TCA cycle

the Calvin cycle

the 3-hydroxypropionate cycle

the reductive acetyl-CoA pathway

9.

1 point

The amino acid biosynthetic pathways are designated as families. Which family generates only one amino acid?

pyruvate family

aspartate family

serine family

histidine family

10.

1 point

In anaplerotic reactions:

intermediates in a pathway are regenerated

nutrients are imported from the environment

molecules targeted for breakdown are salvaged for anabolism

all of the above

11.

1 point

The most ancient CO2 fixation pathway in methanogens is:

the reverse TCA cycle

the reductive acetyl-CoA pathway

the Calvin cycle

the 3-hydroxypropionate cycle

12.

1 point

In the mechanism of nitrogen reduction, __________ directly takes the place of the H2 in the FeMo subunit of the enzyme nitrogenase.

N2

NH3

HN=NH

H2N-NH2

13.

1 point

Microbial biosynthetic processes require:

essential elements

reduction

energy

all of the above

14.

1 point

Which pair is NOT matched correctly?

coenzyme B12—cobalt

chlorophyll a—magnesium

bacteriochlorophyll—magnesium

none of the above

15.

1 point

In oxygenic photosynthesis, __________ is the electron donor, whereas in anaerobic photosynthesis it can be succinate or __________.

H2S; S0

H2O; H2S

O2; H2

O2; H2O

16.

1 point

The term “genome degeneration” refers to:

irreversible

the loss of a particular biosynthetic pathway when an organism becomes dependent on other species in the environment

catabolic

the genetic regulatory mechanisms triggered after bacteria are exposed to UV

17.

1 point

In purple bacteria, bacteriochlorophylls are supplemented by accessory pigments called:

chlorophylls

thylakoids

antenna complexes

carotenoids

18.

1 point

The chlorophyll chromophore consists of a heteroaromatic ring complexed to a:

magnesium ion

potassium ion

calcium ion

chloride ion

19.

1 point

Chorismate is used in a branched pathway to synthesize:

purines and pyrimidines

polyketide antibiotics

fatty acids

aromatic amino acids

20.

1 point

Which of the following is NOT correct regarding secondary metabolites produced by free-living microbes?

Many of them are used as antibiotics.

Some secondary metabolites can inhibit the growth of competitor microbes.

They are sources of carbon, nitrogen, and other elements in anabolic pathways.

none of the above

21.

1 point

Rubisco catalyzes the reaction:

CO2 + ribulose 1,5-bisphosphate → 2,3-phosphoglycerate

HCO3– + acetyl-CoA → malonyl-CoA + NADPH → 3-hydroxypropionate

H2S + light → S0 + 2 H+ + 2 e–

none of the above

22.

1 point

Which of the following molecules provides a way to simultaneously assimilate one carbon atom and one nitrogen atom during purine biosynthesis?

carbamoyl phosphate

acetyl-ACP

acetyl-CoA

malonyl-ACP

23.

1 point

Cyanobacteria have __________-based photosynthesis and are the only __________-producing bacteria.

H2O; O2

H2S; S0

succinate; O2

Mg2+; NO

24.

1 point

Which molecules use 5-phosphoribosyl-1-pyrophosphate (PRPP) in their biosynthesis?

nucleotides

amino acids

tetrapyrrole

fatty acids

25.

1 point

Which of the following is the reducing agent in the saturation step of polyketide biosynthesis?

ferredoxin

NADH

H2

NADPH

26.

1 point

Which of the following is the foundation of most biologically active tetrapyrrole derivatives?

5-aminolevulinic acid

chlorophyll

uroporphyrinogen III

heme

27.

1 point

What types of bacteria perform the reductive pentose phosphate cycle to fix CO2?

cyanobacteria

purple phototrophs

lithotrophs

all of the above

28.

1 point

Where is the catalytic site of Rubisco located?

large subunit

small subunit

a cavity that forms between the LSU and an SSU

none of the above

29.

1 point

The Calvin cycle is essentially:

started by the oxygen capture by Rubisco

a reductive pentose phosphate cycle

the reductive, or reverse, tricarboxylic acid cycle

none of the above

30.

1 point

What is the direction of the proton current in the chloroplast F1Fo ATP synthase during ATP synthesis?

from stroma to cytoplasm

from lumen to stroma

from cytoplasm to stroma

from stroma to lumen

31.

1 point

Which of the following molecules links glycolysis with the TCA cycle, and also serves as a precursor for many biosynthetic products?

acetyl-CoA

succinate

malate

citrate

32.

1 point

In the reductive TCA cycle, four or five ATPs are used to produce one oxaloacetate. How many molecules of CO2 are fixed in this cycle?

3

4

5

2

33.

1 point

Which of the following is a common component of photolytic electron transport systems?

antennae system

electron carriers

energy carriers

all of the above

34.

1 point

Which pathway is utilized for carbon fixation in chloroplasts and cyanobacteria?

the 3-hydroxypropionate cycle

the reverse tricarboxylic acid cycle

the reductive pentose phosphate cycle

the acetyl-CoA pathway

35.

1 point

Biological nitrogen fixation is energetically expensive. Assuming that NADPH is used as the reducing equivalent, how many ATPs are used in the enzymatic conversion of N2 to NH3?

48

16

32

64

36.

1 point

Which of the following pathways is NOT a route for CO2 assimilation?

reductive acetyl-CoA pathway

gluconeogenesis pathway

hydroxypropionate cycle

reductive pentose phosphate cycle

37.

1 point

Variations of the tetrapyrrole ring structure enable coordination to different __________ ions.

metal

halogen

organometallic

all of the above

38.

1 point

What kind of reaction is the formation of oxaloacetate from phosphoenolpyruvate?

anabolic

anaplerotic

carboxylation

all of the above

39.

1 point

__________ and __________ are unique in that they fix CO2 as their sole carbon source.

Organotrophs; iron oxidizers

Photoheterotrophs; chemiolithotrophs

Photoautotrophs; lithotrophs

none of the above

40.

1 point

This molecule CANNOT freely cross biological membranes:

O2

NH3

CO2

NH4+

41.

1 point

Electron donors for anaerobic photosystem I in green sulfur bacteria include:

H2S

organic molecules

Fe2+

all of the above