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Microbio 3220 > Exam 2 - Lecture 12 > Flashcards

Exam 2 - Lecture 12 Flashcards

1
Q

many _____________ _____________ are used as starting substrates for amino acids

A

precursor metabolites

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2
Q

what atom is a major component of protein, nucleic acids, coenzymes, and more?

A

nitrogen

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3
Q

what are potential sources of nitrogen used by cells?

A
  • ammonia (NH3)*
  • nitrate (NO3-)*
  • nitrogen gas (N2)
  • *most cells use these
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4
Q

why is ammonia easily incorporated into organic material?

A

it is more reduced than other forms of inorganic nitrogen

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5
Q

ammonia is added to ______-_____________ under high ammonia conditions to form ______________

A

alpha-ketoglutarate; glutamate

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6
Q

what enzyme transfers amino groups to carbon skeletons?

A

transaminases

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7
Q

what enzyme reduces nitrate to nitrite?

A

nitrate reductase

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8
Q

what enzyme reduces nitrite to ammonia?

A

nitrite reductase

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9
Q

what enzyme catalyzes the reduction of atmospheric nitrogen (N2) to ammonia?

A

nitrogenase

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10
Q

what organisms have nitrogenase?

A

only bacteria and archaea

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11
Q

how many ATP and electrons does it cost the cells to reduce N2 to NH3? what % of cellular ATP can this process consume?

A
  • 16 ATP and 8 electrons
  • up to 20% cellular ATP
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12
Q

which two amino acids have sulfur groups?

A

cysteine and methionine

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13
Q

what is an example of a coenzyme that contains sulfur?

A

coenzyme A

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14
Q

where is sulfur commonly obtained from?

A
  • external sources
  • intracellular amino acid reserves
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15
Q

sulfate (SO4,2-) has to be ________ in order to be incorporated into organic molecules

A

reduced

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16
Q

what is assimilatory sulfate reduction?

A

sulfate is reduced into hydrogen sulfide (H2S) and then is used to synthesize cysteine. cysteine is then used to make sulfur contained organic compounds

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17
Q

what is the first step in assimilatory sulfate reduction? how many ATP does it use?

A
  • sulfate activation through the formation of PAPS (phosphoadenosine 5’-phosphosulfate)
  • uses 2 ATP
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18
Q

what takes place after sulfate reduction in assimilatory sulfate reduction? how many NADPH are used?

A
  • sulfate in PAPS is sequentially reduced to sulfite (SO3-) and H2S
  • 2 NADPH used
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19
Q

what is the final step of assimilatory sulfate reduction?

A

H2S is used to create cysteine

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20
Q

how do fungi make cysteine? how about bacteria?

A
  • fungi: H2S + serine
  • bacteria: H2S+ O-acetylserine
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21
Q

what is transamination? what serves as the source of the amino group?

A
  • the direct addition of amino groups to precursor metabolites to make some amino acids
  • glutamate
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22
Q

glutamate + pyruvate = ?

23
Q

glutamate + oxaloacetate = ?

24
Q

what is an amino acid biosynthetic pathway?

A

when the carbon skeleton is first modified in a precursor metabolite and that single precursor gives rise to several amino acids

25
what four amino acids can be made biosynthetically from oxaloacetate?
threonine, methionine, lysine, and isoleucine
26
what is a nucleoside?
nitrogenous base + 5 carbon sugar
27
what is a nucleotide?
nucleoside + phosphate (base + sugar + phosphate)
28
which end of DNA has the phosphate? how about the hydroxyl?
- 5'-phosphate - 3'-OH
29
what are the purines? are they made of one or two rings?
- adenine and guanine - 2 joined, cyclic rings
30
what are the pyrimidines? are they made of one or two rings?
- cytosine, uracil, and thymine - single ring
31
how many steps is the purine biosynthesis pathway?
11 complex steps
32
what is the base of all purine molecules?
ribose-5-phosphate
33
what is the first purine product formed? all initial products are _______________
- inosinic acid - ribonucleotides
34
how are purine deoxyribonucleotides made from ribonucleotides?
by the reduction of the 2'-OH to a 2'-H
35
what are the first two pyrimidines made?
(deoxy)uridine and (deoxy)cytidine
36
what are the starting molecules for pyrimidine biosynthesis?
- aspartic acid - high energy carbamoyl phosphate - (and bicarbonate and glutamate)
37
what is the important difference between purine and pyrimidine biosynthesis?
- purine rings are synthesized while attached to ribose - ribose is added AFTER synthesis of the pyrimidine ring
38
what % of Earth's surface is water? what % of that water is freshwater and salt water?
- 70% of the surface - 97.5% salt, 2.5% fresh
39
what are important physical factors for microbes in aquatic environments?
- dissolved O2 (most important) - dissolved CO2 - temperature - pH - light penetration
40
in the very deep ocean, oxygen concentration __________ with depth
increases
41
in warm environments, oxygen may become _________ a few meters below the surface
limited
42
the constant exchange of CO2 at the water's surface is called the:
carbonate equilibrium system
43
what is high levels of atmospheric CO2 causing in the carbonate equilibrium system? what does this do to the water?
- higher CO2 dissolution into seawater - it decreases the pH
44
what is an estuary?
a semi-closed coastal region where a river meets the sea
45
what is the characteristic salinity profile of an estuary called?
a salt wedge
46
microbes in estuaries must be able to withstand large changes in salt concentration. what is their salt requirement?
halotolerant
47
are estuaries nutrient rich or poor?
rich
48
what is eutrophication? can this lead to algal blooms?
- enrichment of an ecosystem with chemical nutrients, typically compounds containing phosphorus and nitrogen, which can be caused by pollution - yes
49
what are harmful algal blooms?
HABs are blooms that occur when a single microbial species (algae or cyanobacteria) grows at the expense of other members of the community
50
what toxins are released by cyanobacteria into the environment from the algal blooms in Lake Erie?
microcystins
51
drinking or swimming in algal blooms can cause _________
illness
52
what are two ways algal blooms harm other members in the community?
- strips all the oxygen from the water - photosynthesizing microorganisms and plants can't get light
53
what is the euphotic zone?
the range of water depth where light penetrates with enough intensity so that the rate of photosynthesis by microscopic autotrophs exceeds the collective rate of respiration - basically there's enough light for photosynthesis here
54
what microbe is the most numerous in marine ecosystems?
virioplankton

Microbio 3220 (24 decks)

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