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LSCI230 (Microbiology) > Lecture 4 > Flashcards

Lecture 4 Flashcards

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1
Q

what are the 2 groups that is used to classify metabolism of microorganisms?

A
  1. o2 requirement

2. source of energy, electrons and C

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2
Q

what are the 3 groups of microorganisms based on o2 requirement?

A
  1. aerobes: requires o2 for growth
  2. anaerobes: o2 not needed
  3. facultative aerobe: o2 not required but enhances growth rate
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3
Q

classes of microorganisms based on energy sources?

A
  1. chemoorganotrophs: energy sources are organic chemicals
  2. chemolithotrophs: energy sources are inorganic chemicals
  3. phototrophs: light
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4
Q

classes of microorganisms based on C sources?

A
  1. heterotroph: C from organic chemicals

2. autotrophs: C from Co2

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5
Q

when does fermentation occur?

A

when nothing can act as the final electron acceptor

doesn’t use ETC

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6
Q

what are the 2 pathways in anaerobic conditions?

A
  1. fermentation

2. anaerobic respiration

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7
Q

what is used as the final electron acceptor in anaerobic resp? how do they compared to o2 in energy yield? (redox tower)

A

something other than O2

if molecule is higher in redox tower than o2 = can produce less ATP = less efficient

if molecule is lower in redox tower = can produce even more energy than o2
(usually toxic = rarely found)

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8
Q

what are denitrifying bacteria?

A
  • when N is used as final electron acceptor in anaerobic conditions
  • nitrate (NO3-) becomes Dinitrogen (N2)
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9
Q

how much H+ is pumped out in nitrate based anaerobic resp vs oxidative?

A

nitrate based: 6H+
oxidative: 8H+

[?]

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10
Q

sulfate reduction vs nitrate in ATP production?

A

sulfate is higher than nitrate in redox tower = generates less ATP

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11
Q

2 types ofsulfate and sulfur reduction rxns

A
  1. desulfuromonas:
    - terminal e- acceptor: sulfur (rotten egg smell)
    - e- donors: acetate, ethanol
  2. desulfovibrio:
    - terminal e- acceptor: sulfate or sulfite
    - e- donor: organic or inorganic compounds
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12
Q

2 groups of phototrophs?

A
  1. photoautotrophs:
    - uses Co2 as C source
    - needs environment with lots of light
  2. photoheterotrophs
    - uses organic compounds as C source
    - lives in environment with less light

light energy = used to generate a pmf

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13
Q

what is oxygenic and anoxygenic photosynthesis?

A

oxygenic: electrons are taken from H2O (H2o is oxidized to O2)
anoxygenic: doesn’t produce o2. source of electrons are sulfides = produces sulfate)

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14
Q

role of LH1 and LH2?

A

funnels light energy to the reaction center where the reaction occurs

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15
Q

what pigments participate in the photosynthesis reaction?

A

only the pigments in the reaction center

ie P680, P700, P840

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16
Q

primary role of carotenoids?

what happens when there is too much bright light?

A

protect system against bright light

too much light = too much energy = produces toxic forms of o2 = harmful to organism

17
Q

function of phycobilins?

A

forms complexes with proteins that are main light harvesting systems = gives another peak of absorbance to the complex

found in microorganisms with very little light environment = allows more production of ATP

18
Q

site of photosynthesis in plants and algae?

A

chlorophyll in the chloroplast

19
Q

describe the pmf across the thylakoid membrane

A

H+ pumped to interthylakoid space

inside becomes positive and acidic

stroma becomes alkaline and negative

20
Q

photosynthesis site in bacteria?

A

pigments are inetegrated in internal membranes

either cytoplasmic, intracytoplasmic, thylakoid membranes or chlorosome

21
Q

what is the best photosystem to capture light at low intensity??

A

chlorosome (in green sulfur and green nonsulfur bacteria in deep aquatic habitats)

has antennae systems that transfer light to the RC

22
Q

describe photosynthesis in purple bacteria

A

anoxygenic photosynthesis:

needs electron source to reduce NAD+, but P870* does not have enough energy to produce NADH

NADH is produced by reverse electron flow

  • energy is supplied by pmf
  • electrons are transferred to NADH dehydrogenase (complex 1)
23
Q

what is the goal of reverse electron flow

A

to reduce NAD+ to NADH by using energy from pmf when there is not enough light energy

less efficient in producing ATP

24
Q

describe cyclic photophosphorylation

A

light is funnelled to the RC > RC is good electron acceptor when in resting state > RC is energized when it receives light > electrons are pushed down the redox tower which allows energy to be harvested > electron goes back to first state > RC is ready to accept another electron

25
Q

Describe anoxygenic photosynthesis in green sulfur bacteria

does it use reverse electron flow?

A

doesn’t use reverse e- flow because there is enough energy in the system already (starts higher on the redox tower = NAD+ can be reduced to NADH)

26
Q

describe photosynthesis in algae and cyanobacteria

A

noncyclic photophosphorylation + no reverse electron flow = very efficient

e- is taken from H2O > H2O is reduced to O2 > pmf is produced when e- moves down > e- moves to PS1 > e- is excited by light > another pmf is produced > e- is used to reduce NAD+ to NADH

27
Q

when is there cyclic or non cyclic phosphorylation?

A

cyclic: when reducing power is sufficient for the cell’s needs. No need for an electron source

non cyclic:needs creation of a pmf to drive ATPase. Not enough reducing power (not high enough on redox tower)

28
Q

describe anoxygenic photosynthesis in some cyanobacteria

A

PS2 is inhibited by H2S = only PS1 is functioning

pmf drives cyclic phosphorylation at PS1

29
Q

what are primary producers (chemoautotrophs)?

A

chemoautotrophs that can live without organic C present

they produce their own C from CO2 (carbon source)

30
Q

what are nitrifying bacteria?

what are the groups?

A

Organisms that use inorganic nitrogen compounds as electron donors (ie NH3 or NO2-

groups:

nitrosomonas: oxidizes ammonia to nitrite
nitrobacter: oxidzes nitrite to nitrate

31
Q

what is NO2- and NO3-?

A

NO2- is nitrite

No3- is nitrate

32
Q

do nitrifying bacteria need O2?

A

yes. only grows in aerobic conditions b/c O2 is the final electron acceptor

33
Q

does nitrosomonas and nitrobacter use reverse e- flow?

what is the final electron acceptr?

high or low ATP yield?

A

yes

final e- acceptor: o2

very low ATP yield (b/c reverse e- flow is energy demanding but produces very low ATP

34
Q

describe sulfur bacteria energy production.

final e- acceptor?

products?

A

oxidized sulfur compounds

final e- acceptor: o2

products: so4^2- (sulfide) and protons (sulfuric acid)

35
Q

describe how methanogens produce energy

A

produces CH3

anaerobes (found in marches, anaerobic sediments, intestinal tract, etc…)

2 diff pathways:

  1. reduces CO2 by using H+
    - converts Co2 into organic material
    - H is energy source
    - uses Na+ motive force
  2. acetate as source of energy and C
    - uses pmf
36
Q

describe methanotrophs

A

aerobes

burns methane (CH4) as carbon and energy source

pumps 10 protons (high ATP yield)

37
Q

difference between methanotrophs and methanogens?

A

methanogens:
- anaerobes
- produces CH4

methanotrophs:

  • aerobes
  • burns CH4 (reactant, not product)
38
Q

location of calvin cycle in euk vs prok?

A

euk: stroma of chloroplast
prok: cytoplasm

LSCI230 (Microbiology) (4 decks)

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