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BIO239 Microbiology And The Cycles Of Life > L6 Phototrophy > Flashcards

L6 Phototrophy Flashcards

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1
Q

What is captured to generate enrgy in phototrophy

A

Photon (light)

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2
Q

What can capture light

A

Chlorophyll
Bacteriorhodopsins
Accessory pigments

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3
Q

What do photoautotrophs do

A

Link energy generation and cabon sioxide biomass fixation in the Calvin cycle

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4
Q

What do photoheterotrophs do

A

Harvest energy (ATP) from light and use organic carbon sources for biosynthesis

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5
Q

The excited electrons are responsible for..

A

Driving the electron transport system / proton pumping

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6
Q

What is the cycle in chlorophyll photosystems

A

Double-cycle Z pathway

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7
Q

How can light collection be maximised

A

Packing membranes with photoreceptors

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8
Q

What are 3 events that can follow after electron excitation

A

Electron transferred
Energy transferred (resonance) to another electron
Returns to ground state (energy transformed)

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9
Q

What is the most common result of an excited electron in phototrophy

A

Energy transferred (resonance) occurs commonly in photosystems

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10
Q

What wavelength of light is absorbed by bacteriorhodopsin / proteorhodopsin

A

Green wavelength

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11
Q

What groups of microbes do bacteriorhodopsin and proteorhodposin belong to

A

Bacteriorhodopsin = archaea
Proteorhodopsin = bacteria

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12
Q

What percentage of marine bacteria contain proteorhodopsin and how was this discovered

A

13%
Metagenome analysis

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13
Q

What occurs once photons have been absorbed by bacteriorhodopsins and electrons have been excited

A

Change binding in retinol and alter shape of protein
Binds H+ to one side of membrane
Releases on other side of membrane as it returns to ground state
Proton gradient used to generate ATP

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14
Q

What is photolysis

A

Light absorption coupled with splitting a molecule

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15
Q

What absorbs light in purple bacteria

A

Light harvesting centres LH1 and LH2

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16
Q

Hat absorbs light in green bacteria

A

Chlorophyll

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17
Q

What are the carotenoids in purple bacteria

A

Rhodopin and rhodopinal

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18
Q

What are the carotenoids in green bacteria

A

Carotenes e.g. Chlorobactene and isorenieratene

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19
Q

What is phycobilisome

A

Highly structured array of pigments in cyanobacteria antenna (allophycocyanin, phycocyanin and phycoerythrin)

20
Q

Where are phycobilisomes found

A

Bound to thylakoid but not embedded in the membrane

21
Q

What is the light absorbing molecule in a low vs high energy system

A

Low = bacteruichlorophyll and carotenoids
High = chlorophyll a and b and accessory pigments

22
Q

What is the wavelength of light absorbed in low vs high energy systems

A

Low = infrared, ultraviolet, green
High = red and blue

23
Q

What are the associated organisms in low vs high energy systems

A

Low = anaerobic heterotrophs such as green and purple bacteria
High = aerobic photoautotrophs e.g. Cyanobacteria

24
Q

What do green and purple bacteria hydrolyse

A

Hydrogen sulfate (H2S)

25
Q

What is released when green and purple bacteria hydrolyse H2S

A

Elemental sulphur or sulphate release

26
Q

What kind of light penetrated furthest down the water column

A

Infrared

27
Q

What kind of accessory pigments do purple vacteria ocntain
What wavelength of light do they absorb

A

Caeotenoid accessory pigments
Absorb green light

28
Q

Esplain the steps in the green / purple sulfur bacteria photosystem ehich create the membrne gradient

A

Absorbed photon energy is transferred to ets in membrane
Electron transferred from H2S
Electron is transferred via ferredoxin to make NADPH
Hydrogen splits from H2S making H+ gradient across membrane

29
Q

Explain the difference in the photosyetm of purple non-sulfur bacteria

A

Much lower energy is absorbed, not enough to reduce NADP to NADPH directly
H+ is transferred to create gradient for ATP synthase motor
Cyclic phosphorylation

30
Q

What wavelengths of light does chlorophyll absorb

A

Red and blue

31
Q

Which bacteria is the only one to use both photosystems I and II

A

Cyanobacteria

32
Q

What are 3 components of cyanobacterial cells

A

Thylakoids
Lipid and gas vesciles
Carboxysome bodies

33
Q

Which microbes carry out aerobiv photosynthesis in the Winogradsky column

A

Cyanobacteria and algae

34
Q

What is the role of microbes carrying out aerobic photosynthesis in the Winogradsky column

A

Release oxygen to be used by aerobic heterotrophs
Fix carbon into the system from carbon dioxide
Cyanobacteria are also able to fix nitrogen

35
Q

What microbes carry put anaerobic photolysis in the Winogradsky column

A

Green sulphir bacteria
Purple sulohur bacteria
Purple non-sulphir bacteria

36
Q

What do purple non-sulphir bateria fix
What is their nutritional mode

A

Fix carbon dioxide
Use hydrogenetrophy or heterotrophy

37
Q

What determines the limit for purple non-sulphir bateria growth

A

Sensitive to hydrogen sulphide

38
Q

What is the nutritional mode of purple sulphur bacteria and how is this carried out

A

Largely photoheterotrophic, can respire anaerobically
Split H2S to S

39
Q

What is the nutritional mode of green sulphir bacteria
How do they achieve this
How do they fix carbon dioxide

A

Photoautotrophic
Splie H2S
Reverse TCA cycle to fix CO2

40
Q

What are 3 alternative methods of arbon fixation besides the Calvin cycle

A

Reverse TCA cycle (green sulphur bacteria)
Acetly-CoA pathway
3-Hydroxypropinate cycle

41
Q

Where is Rubisco found

A

In carboxysomes

42
Q

What converts HCO3- to carbon dioxide

A

Carbonic anydrase

43
Q

What prevents diffusion of carbon dioxide in carboxysomes

A

Polyhedral protein shell

44
Q

What microbes carry out the reverse TCA cycle

A

Green sulphur bacteria
Sulphur-reducing archaea
Epsilonproteobacteria in hydrothermal vents

45
Q

What microbes use the Acetly-CoA pathway

A

Methanogens, soil anaerobes, autotrophic sulphur reducers

46
Q

What microbes use the 3-Hydroxypropinate cycle

A

Sulphir oxidisers

47
Q

What is a chlorosome

A

The antenna complex of green bacteria - mainly carotenes (chlorobactene + isorenieratene)

BIO239 Microbiology And The Cycles Of Life (12 decks)

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