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Photosynthesis > Lecture 1/29 > Flashcards

Lecture 1/29 Flashcards

1
Q

What do we know of current bacteria diversity?

A

Photosynthesis is assembled from bacteria components that evolved through a process of endosymbiosis and lateral gene transfers.

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2
Q

What were the main points in the nature paper “Biomarkers evidence for green and purple sulfur bacteria in stratified Paleoproterozoic sea”?

A

What they did:
Looked at a set of rocks, crushed them and extracted the organic matter in liquid organic fractions.
What they found:
Found membrane components ->helped point out what bacteria were there.
Found pigments -> eg carotenoids, IMPT bc part of the photochemistry and metabolism was able to ID through the pigments to a set of bacteria.

Overall, was able to reconstruct the ecology of the ocean 2.5 Ma.

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3
Q

Who was CB Van Niel and what was this contribution?

A

Dutch biochemist. And he came up with the general equation of photosynthesis. He connected that photosynthesis was a life process connected to a redox process.

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4
Q

What is anoxygenetic photosynthesis?

A

Process by which energy is obtained from light but does not produce oxygen.
Most organisms use sulfur as their e- donor.

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5
Q

What is photosynthesis?

A

The biochemical process by which light is absorbed and converted into chemical energy, ultimately resulting in the reduction of carbon dioxide to organic carbon.

Occurs in two steps: Light reactions and carbon reactions.

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6
Q

What does light drive in anoxygenic photosynthesis?

A

Only the light reactions are driven by light.

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7
Q

What does light drive in oxygenic photosynthesis?

A

The reducing power that drives the carbon reactions is driven by light.
Light splits 2 waters, releasing oxygen.
This is bc it was two photosystems -> twice the power -> can split water

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8
Q

What are the main differences in anoxygenic photosynthesis?

A
  • Evolves many times and first
  • Primarily in bacteria
  • Gain reducing power from environmental sources, usually reduced sulfur
  • Pigments and apparatus are integrated into cytoplasmic membrane
  • Produces oxidized compounds (eg SO4^2-)
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9
Q

What are the main differences in oxygenic photosynthesis?

A
  • evolves once (no later than 2.5 Ma)
  • evolved in cyanobacteria into eukaryotes
  • Gain reducing power from splitting water, which is ubiquitous but difficult to split
  • Pigments and apparatus are found in chloroplasts, separate organelles
  • Produces oxygen gas (O2)
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10
Q

Why are plants green?

A

Pigments reflect parts of the EM spectrum they don’t absorb.

Thus, chlorophyll does not absorb green, so organisms with chlorophyll appear green

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11
Q

How does a plant cope with excess energy?

A
  • Fluorescence
  • Heat
  • Energy transfer
  • Photochemistry
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12
Q

How is light absorbed?

A

Light is absorbed by pigments

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13
Q

What are the main photosynethetic pigments? Their parts?

A

Chlorophylls.
They have a tail and head (which was a porphyrin ring).
Tail is anchored to a membrane and the head is where excitation occurs.

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14
Q

How do pigments absorb different wavelengths?

A

Small differences in the functional groups change absorbance wavelengths.
-huge diversity

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15
Q

What are the three main chlorophylls in cyanos and euks?

A

Chlorophyll a, b and c

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16
Q

What organism has chlorophyll a and chlorophyll b?

A

Cyanos, green algae, and terrestial plants

A+ B = GREEN

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17
Q

what organisms have chlorophyll a and c?

A

Red algae

A + C = RED

18
Q

What are the accessory pigments? What do they do?

A

Carotenoids and bilins are accessory pigments: they absorb light and energy. Carotenoids form a protective function. (Act as sunscreen, reason why leaves turn red)
Bilins help generate energy in cyanobacteria.

But chlorophylls are the ones doing all the activity.

19
Q

What are antennae complexes?

A

Aka light-harvesting complexes (LHC).

  • Many pigments together act as antennae - they are arranged spatially in order to obtain as much energy.
  • receive proton, get excited into a higher energy, then pass it to where the redox reaction occurs through resonance transfer.
  • no chemical reactions occur here
  • LHC are arranged around reaction centers
20
Q

What are reaction centers? What happens there?

A

This is where chemical reactions take place.

Energy gets turned to ATP

21
Q

In what direction does energy go?

A

Energy can only move towards the reaction centers, not away from it. Only downhill the energy gradient towards the reaction centers.

22
Q

What makes a photosystem? If there a difference between anoxygenic and oxygenic photosynthesis in regards to their PS?

A

Antenna complexes + reaction center = Photosystem
; light is absorbed by the pigments in PS
Anoxygenic photosynthesis there is one photosystem harvesting the light and doing the redox rxns.
Oxygenic photosynthesis there are two photosystems acting as one.

23
Q

Why are photosystems important in an evolutionary sense?

A

Comparing the biochemistry of different photosystems give us deep insight into how photosynthesis evolved.

24
Q

Where are the antenna complexes and reaction centers embedded? Why?

A

Antenna complexes and reaction centers are embedded in membranes where they can be close to key complexes and set up a proton gradient.
This is then used to generate ATP

25
Q

What is the specialized structure that some bacteria have?

A

Chlorosomes is the specialized structure. They are a sack filled with pigments sitting on top of the reaction center that are good at absorbing light at very low intensities.
(work like a magnifying glass that puts all the light directly to the reaction center)

26
Q

Where are the electrons passed in anoxygenic photosynthesis? Is this process cyclic or linear?

A

Electrons are passed from Chls to quinones to cytochrome complexes back to the reaction center.
This process is CYCLIC in anoxygenic photosynthesis.

27
Q

What is resonance transfer?

A

When there is a transfer of electrons from LHC to the RC. Passing of energy.

28
Q

Describe the process of photosynthesis

A
  • Diff pigments absorb diff wavelengths.
  • Light is absorbed by pigments.
  • Energy is transferred through resonance transfer.
  • Passes through LHC to RC
  • RC gets excited and does redox chemistry.
  • Electron flow generates ATP through ATPase.
29
Q

Is oxygenic photosynthesis cyclic or linear?

A

It is linear

30
Q

What is photophosphorylation?

A

When protons move across the membrane from high concentration to low concentration, in the process passing through the ATP synthase complex.
ADP is phosphorylated to ATP.

31
Q

What electron donors can be used in photosynthesis? What does anoxygenic/oxygenic photosynthesis use?

A

Hydrogen
Sulfide
Ferrous iron
Water

  • Anoxygenic photosynthesis tends to use sulfide or iron as their e- donors.
  • Oxygenic photosynthesis uses water.
32
Q

What do anoxygenic photosynthetic bacteria look like?

A
  • Green sulfur bacteria
  • Green non-sulfur bacteria
  • Purple bacteria
  • Heliobacteria
33
Q

What are some characteristics of green sulfur bacteria?

A
  • have lots of morphologies but little diversity
  • Photoautotrophs
  • Don’t move
  • Have chlorosomes
34
Q

What are some of the main physiology components of Green Sulfur Bacteria?

A
  • Carotenoids: Isorenieratene
  • Uses SULFIDE as ELECTRON DONOR. (makes to sulfate)
  • HAS FE-S at its PHOTOSYSTEM CORE.
  • Like PS1 bc of its Fe-S PS
  • FeS is e-acceptor.
  • Since can’t move, lives with other bac that are sulfate reduces and turn it back to sulfide.

*have chlorosomes and Fe-S complex in PS

35
Q

What are some characteristics of green non-sulfur bacteria?

A
  • motile
  • autotrophic
  • called filamentous anoxygenic phototrophs
  • some stains are facultatively aerobic (can live in environments with O2) others are obligate anaerobes (cant live in o2)
  • When aerobic, lose photosynthesis ability
  • not really related to green sulfur bac
36
Q

What are some of the main physiology components of Green Non-Sulfur Bacteria?

A
  • anoxygenic phototrophs
  • CHLOROSOMES like green S bac
  • QUINONE as electron donor
  • Has quinone-like in PS like PS2
  • Quinone is the electron acceptor
37
Q

What are some characteristics of purple bacteria?

A
  • Proteobacteria
  • Diverse, lots of morphology variety
  • Most use SULFIDE as E-donor
  • Purple sulfur: beta, gamma proteos (can withstand high levels of sulfide)
  • Purple non-sulfur: alpha (able to use sulfide, can’t tolerate high concentrations)
  • anoxygenic phototrophs
  • often use organic rich sediments (where H2S)
38
Q

What are some of the main physiology components of purple bacteria?

A

-anoxygenic phototrophs
-use calvin cycle with rubusco
-uses ANYTHING that gives electron as an Electron Donor
-Has a Quinone-Type Photosystem
(Like PS2)
-Quinone is the electron acceptor
-membranes can be in sheets (lamellae) or clusters (vesicles)

39
Q

What are some characteristics of Heliobacteria?

A
  • Gram positive
  • only known phototrophy in group (little diversity)
  • related to bacteria that are toxic to humans
  • can’t tolerate sulfide or oxygen
  • CAN fix nitrogen (the enzyme that fixes nitrogen gets destroyed by O2)
  • found in soils (land)
  • photoheterotrophs
40
Q

What are some of the main physiology components of heliobacteria?

A
  • Photoheterotroph
  • NO Carbon fixation
  • Electron donor: ANYTHING that will give up e (eg H2S, H2…)
  • Fe-S photosystem (Like PS1)
  • Electron acceptor is FeS
41
Q

In total, what are the come commonalities between the anoxygenic bacteria?

A
  • One photosystem
  • bateriochlorophyll as primary pigment
  • sulfide or hydrogen as the electron donor
  • cyclic electron transport

-Can generate enough energy to live but NOT split water.

42
Q

Which anoxygenic photosynthetic bacteria have photosystems that are similar to PS1/PS2? What is in their core PS?

A

PS1 - Greensr, helio
-They have Fe-S in their core PS
PS2 - Purple, green non-sulfu
-Has quinones in their core PS

Photosynthesis (4 decks)

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